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    • #30271
      Sgt. Mike
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      This past week a member( CA Dude) and I discussed this at work at great length as we was originally discussing barrel burner cartridges and this topic arose.

      Why well simple what is it?

      Where can I find it defined by the original person in print whom used this term whom was PO Ackley in the 60’s in his book?

      What makes a cartridge overbore?

      After our conversation I am of the opinion it is a term without a quantifiable definition except that
      1: I don’t like your cartridge
      2: I don’t think that is as practical as mine
      3: Why burn all that powder for not much gain
      4: Well maybe that is faster than mine, but you’ll burn out a barrel first

      So does that mean there is no such animal as a Overbore cartridge?

      The purpose of this post is to invoke thought not conjunction

    • #30272
      Goodsteel
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      I always defined “overbore” at the point where internal case capacity is at a place where powder burns efficiently, beyond which any gain comes a disproportional cost of powder.
      Take the 30-06. I would consider this a cartridge at the edge of being overbore. Why? Because

    • #30273
      farmerjim
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      This post got me to investigate a case volume to bore ratio chart. I knew the 220 swift was up there, but the position of the 270 win high in the chart surprised me.

    • #30275
      Sgt. Mike
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      Yes, indeed that exact cartridge was brought up.

    • #30276
      JPHolla
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      I believe it is not a technical term, but rather a vague description as well. I think the etymology comes from British parlance simply referring to a bottle-neck case because the case is greater than the size of the bore. Over time, as larger and larger cases were invented with smokeless propellent, it was said that some were “so overbore” they were hard on barrels, etc. I think different people have latched onto the term in slightly different ways, like the ratio of case capacity/bore where the end result is greater than 1000, but the end result is arbitrary. As “overbored-ness” goes up, barrel life and gains go down across the spectrum in a linear fashion; there is no wall where barrel life instantly tanks out.

      Case design also affects barrel life and powder burn efficiency in addition to (or despite) how overbore a case is.

    • #30277
      WCM
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      I think of it in terms of barrel life and efficiency.

      I always liked the .270 win , but never was too crazy about the 7mm Rem Mag.

      I also like the .358 win and never was too crazy about the .348 win although I do like the model 71 rifle.

      We all have our favorites, and what really matters is what works well for you,and what you enjoy shooting.

    • #30279
      lar45
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      The 22-50BMG = OverBore 😉

      I’d say that it is a relative term when compared to the 30-06 as a standard.
      25-06 marginal, 257 Wby = overbore
      All the new 26, 27, 28 Noslers = overbore
      375 and 416 Ruger, all perfectly fine.
      416 Wby, over the line.

      I’d say as long as you’re aware of the potential for reduced barrel life, then go have some fun. Then when it’s time, just have Tim set it back a thread or two and go some more.

      just my .02

    • #30280
      Scharfschuetze
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      With the development of slower burning powders, the number of rounds with an “overbore” reputation has decreased significantly.

      I like to get about 4,000 rounds out of an accurate barrel for match or prairie dog use. The hot 6mm and 6.5mm rifles that are now very popular for long range match shooting will rarely make it to half of that before loosing accuracy. For me, that meets the criteria of “overbore” capacity. Probably doesn’t matter if you only plan to fire a rifle 20 or times a year as a big game rifle, but my rifles will often get 100 times or more use than that.

      I think that the very first “overbore” rounds must have been the 220 Swift, the 244 H&H Magnum and perhaps the 280 Ross.

    • #30281
      Anonymous
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      Well, from a totally different perspective, you obviously have way to much free time at work, and should just get really busy so these mind bending questions aren’t distracting you………………:eek: heh! This is not rocket science, overbore, is the opposite of underbore, see.

    • #30286
      Sgt. Mike
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      LMAO — that is a good one Claude I like that definition.

      But thanks to everyone for your responses

    • #30287
      oldblinddog
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      .22 Eargesplitten Loudenboomer is overbore. [.22-.378 Weatherby]

    • #30289
      Goodsteel
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      I really can’t add to Scharfschuetz reply. Pretty much sums up my stance on it. I mean, what a downer it is to buy, or have built, a rifle that will have to be rebarreled in 1000 rounds?
      All rifles will need a rebarrel at some point. I often tell my clients how many shots they are likely to get before its time for a rebarrel. I council them to follow a procedure whereby every time they finish a box of 100 primers, they should put money in s jar so that when the barrel is toast, they have the funds to get me to rebarrel for them.

      Now, a rifle chambered in a non-overbore cartridge like 308 will require a deposit of only $12-$15, but a 300 Winchester Magnum will be more like $45, and a 6.5X284 will be closer to $60.

      So there’s a very clear example of how “overbore” socks it to you right in the pocketbook.

      The truth is, performance COSTS. Many of the folks who come to me asking for a performance cartridge have no intention of using it to its potential. The last 300WM I built was for a fellow who just couldn’t see that 30-06 would handle 99% of what he wanted to do with his rifle, and 308 would handle 90% of his stated goals.
      He made the choice to cut his barrel life in one third so he could have the privilege of getting beat to death (12 pound rifle) while roastin the crap out of his barrel. Why? Because it’s a Magnum, and 30-06 is just an old hunting cartridge.

      Understanding the concept of “overbore” is a worthwhile point of education.

    • #30291
      WCM
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      I could have done everything I have ever done in large game hunting with a .30/06
      I have owned many of the magnum ,and standard calibers.
      The older I get the less I like recoil.

    • #30297
      Sgt. Mike
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      Gentlemen again what is over bore?

      What make a cartridge over bore for it’s bore, and where is it written?

      What is the capacity level of a case that defines it overbore for the bore used in that barrel?

      Can I correct a overbore by extending the length?

      I have never seen a truly across the board accepted definition of what determines overbore.

      I am not discussing barrel erosion or shot out barrels that is a result of certain conditions.
      1. Rate of Fire – allowing a barrel to get too hot quickly. nothing says that if I’m testing for a 30 shot group that I can’t take 1 hour or more to shoot it.
      2. Poorly machined throat or bore
      3. Heat treatment of the barrel (stress relief) before and after land and groove being bored or machined
      4. Use of Slower powder for pressure range = more heat to the bore
      5. Allowing carbon build up in the throat….. face it some of ya’ll don’t clean the barrel. and when it hardens it is highly abrasive. BTW it doesnt take much to get it to harden.
      6. Barrel alloy tolerances in the manufacturing process of the materials from the foundry
      7. Improper cleaning such as allowing harsh chemicals to sit too long, using wrong size rods, excessive exiting and drawing back in of the crown non use of a bore guide to help with reducing rubbing a steel or aluminium rod against the bore.
      8. Coating on the powder used, some are more abrasive than others although those same coating exhibit other desirable characteristics (burn rate or temperature insensitivity)
      9. Break in procedures of a new barrel
      10. Twist rate
      11. etc etc you get the idea.

      Tim and others have heard me brag on the 30-06, However at one time this was considered a overbore cartridge. What happened to change this? Maybe powder development that allowed a higher expansion rate and less abrasive properties than earlier used powders, or maybe dialling pressures back?

      Look at the 22-250 versus the 220 Swift both has the same bore, the swift has a larger case capacity but if we use the definition of barrel life the 22-250 has a less accurate barrel life than the 220 Swift as reported by the experts.

      In the 6mm family same goes for the .243 Winchester versus the 244 Remington aka 6mm Remington, Ever consider why the larger capacity case get a higher rounds count over the smaller case that runs at pretty much the same level.
      Some have even claimed higher rounds count from longer barrels.

      I would highly suggest a close inspection of the shoulder angles and neck length in both examples, where is the turbulence point? Could that be a factor?

      Also bear in mind that barrel life is not always defined as 1 moa.
      So do we consider barrel life as done when we sling a bullet sideways? Or when it holds minute of barn, or when it exceeds .250 moa? Some barrels will only hold 3 MOA brand new. Barrel life and accuracy is defined by the user, not anyone else, some barrels get better life than others for reasons listed above. Even in the cartridges that have less usable barrel life.

      I can burn a barrel out in a 308 faster than the normal accurate accepted level does that make that cartridge overbore??
      I can burn a 308 Winchester cartridged barrel in 800 rounds easily.

      Within this discussion I can negate the use of short barrel life as a definition of overbore by simply asking what is the accepted rounds count for a certain bore. Hence is why I offered my definition

      1: I don’t like your cartridge
      2: I don’t think that is as practical as mine
      3: Why burn all that powder for not much gain
      4: Well maybe that is faster than mine, but you’ll burn out a barrel first

      Deep subject?
      Everyone has responded with logical and normally accepted responses, but never truly answered the question. But then again I can’t truly answer this either except to offer what I did.

    • #30299
      CA Dude
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      Overbore is clearly a undefinable term. I see it as a math problem: Is efficiency and barrel life more or less important than performance. Efficiency = powder used to achieve X performance (velocity). Barrel life = numbers of rounds fired to achieve X performance (accuracy). The wild card is performance. Do you really need 4000 fps to kill a prairie dog standing on the mound 200 or 400 yards away? The best thing about shooting; no one has to show a need, a want is good enough. Does a rifle that can no longer hit that prairie at 400 yards because it has had 4000 rounds fire through it need a new barrel, or can it still be used on bigger and closer targets? I think Tim covers on the consequences of this performance issue very well. Shooting is a lot like the Army; you can do anything you can afford. In the Army, the cost is rank. In shooting, the cost is a new barrel. And I think we are all cool with that.

    • #30300
      Sgt. Mike
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      Ed about time you responded, been trying to bait you into posting as you are really bad to lurk.
      Now you need to post some of your 300 Savage stuff I think many would respond favourably. I know many would like that 400 Whelen when you get it going.

    • #30301
      Sgt. Mike
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      Ed about time you responded, been trying to bait you into posting with this topic as you are really bad to lurk.
      Now you need to post some of your 300 Savage stuff I think many would like to see your progress with that rifle.
      I know many would like that 400 Whelen when you get it going.

    • #30303
      Artful
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      http://www.accurateshooter.com/techn…ed-by-formula/


      John notes that there is no generally accepted definition of “overbore”. Based on analyses of a wide variety of cartridges, John hoped to create a comparative index to determine whether a cartridge is more or less “overbore”. This, in turn, might help us predict barrel life and maybe even predict the cartridge’s accuracy potential.

      OVERBORE INDEX Chart

      So what do these numbers mean? John says: “My own conclusion from much reading and analysis is that cartridges with case volume to bore area ratio less than 900 are most likely easy on barrels and those greater than 1000 are hard on barrels.” John acknowledges, however, that these numbers are just for comparison purposes. One can’t simply use the Index number, by itself, to predict barrel life. For example, one cannot conclude that a 600 Index number cartridge will necessarily give twice the barrel life of a 1200 Index cartridge. However, John says, a lower index number “seems to be a good predictor of barrel life”.

      John’s system, while not perfect, does give us a benchmark to compare various cartridge designs. If, for example, you’re trying to decide between a 6.5-284 and a 260 Remington, it makes sense to compare the “Overbore Index” number for both cartridges. Then, of course, you have to consider other factors such as powder type, pressure, velocity, bullet weight, and barrel hardness.

      And yes I think the changes to powder formulations do change perceptions of cartridges that once were considered “Overbore”

    • #30304
      Sgt. Mike
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      Art seen that was well earlier when I was looking prior to posting the question and actually considered about using it. (think it was posted on accurate shooter) Thank you for weighing in with that article.
      I for the record do like Scharfschuetze’s as well as everyone’s reply on the topic as I agree with much as what has been said. And I don’t see where anyone is wrong. I do see where metallurgy, changes in machining process,and powder development have lessened certain barrel burner cartridge to a acceptable level.
      Earlier I alluded to the turbulence point based on the cartridge shoulder angle and neck length. A quick looking into that borne some interesting thought on this. Consider the large straight wall rifle cartridge never heard anyone refer to them as overbore or as barrel burners. Maybe because of a lack of a turbulence point for the powder column and escaping gasses? In CA Dude and my conversation this was thrown out as theory. ( and of course naturally more powder just accelerates the process)
      This does not discount the index that was shown but I am of the opinion that a modifier is in order to refine the math. I will agree it is as good or better merit system that I have seen offered thus far.

    • #30306
      Goodsteel
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      I’ll be dogged. Just realized with Sarge’s comment who you are! It’s the master sergeant himself! Had a great time Saturday sir! We need to get together again sometime!

      Ric’s 308 loads ended up doing 5/8″ groups. Sarge was spotting. After Sarge left, and Ric shot the sweet group, he was very appreciative to both of you.

    • #30308
      Rattlesnake Charlie
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      Sgt Mike, good job stirring things up!

      There are mathematical calculations of case capacity to bore diameter, but still there is no accepted by everyone definition of overbore. I think it being the opposite of underbore is the most precise definition proffered.

      I am not allowed entry into the club of overbore fans. The only calibers in bottle necked cartridges I own are .223, 7.62 x 25, 7.32 x 39, .308, .30-06, 7.62 x 54R and .375 H&H. I’m so boring. I think I’ll go load some .45-70.

    • #30309
      Harter
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      I’m not sure I have had anything under bore ….
      I guess maybe I did have a couple that would be slightly under 900 using the above list.

    • #30310
      Sgt. Mike
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      Thank you Charlie, Kinda why I asked the question and posed it like I did. As well as draw CA Dude into the conversation.

      Invoke thought on what some folks hear and interpret.
      I don’t know for a fact but in a conversation today CA Dude and I highly suspect that PO Ackley really meant to dub a term to be used against Mashburn and his cartridges because of competition. That maybe why he never defined what a overbore really was when he introduced the term allowing shooters to draw a negative condemnation of Mashburn designs. Just a thought.

      Much like the 3 shot group versus the ten shot group that Jack O’ Connor championed with the statement that he could evaluate the hunting accuracy of a express rifle within three shots. That statement took hold and grew from there to normal hunting rifles when the norm was indeed 10 shot groups.

    • #30311
      WCM
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      My smallest centerfire rifle is the .22 Hornet,and my most powerful centerfire is the .375H&H.
      I have also owned a .458 win mag,and a .416 Rem Mag.
      My most efficient cartridge is probably the .22PPC

      I guess some people would consider many of the Weatherby cartridges overbore.
      I personally like them,and believe they offer something more in performance.

      I have checked my .270 Weatherby with factory ammo using an Oehler 33 chronograph .
      I get 3600 fps with the 130 gr load.
      I have tried to match the ballistics with handloads and failed.

      The powder looks like Norma MRP, but is not.

    • #30313
      Scharfschuetze
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      I wonder if powder burning efficiency and velocity might also be considered in the discussion.

      If we use the 30/06 (915 on the chart above) as a base line, it often gets over 50 fps per grain of powder at maximum charges. If you look at loading charts for the 300 Remington Ultra Mag with the same weight bullets, it is often only getting about 25 fps per grain of powder. While it’s velocity is obviously greater, it’s burning much more powder per foot pound of energy than say our base line cartridge. 18% higher velocity for an expenditure of 29% more powder. Both figures are based on 180 grain jacketed spitzers over 4831 powder in the two cartridges.

    • #30315
      Rattlesnake Charlie
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      I need more coffee.

    • #30317
      Sgt. Mike
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      Scharfschuetze, What about the 30-40 krag thrown in

      CartridgeCase Cap H2OCase cap CC4831 gr /180gr bulletVol of charge CCs% of fillvelvel per GrVel per CCPressurePressure per gr
      30-40583.9493.693.1%242549.5627.235900732.7
      30-06694.656.84.290.8%274948.4597.6571001005.3
      300 WM895.970.25.287.0%291641.5491.559700850.4
    • #30318
      Goodsteel
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      The Weatherby cartridges are the epitome of “overbore”. That doesn’t mean they are bad, and overbore is just a way of saying “you pay for performance” but performance is there otherwise it wouldn’t be overbore. Weatherby cartridges are high performance cartridges, and if I built a target rifle on that platform, it would usually get about 800-1500 rounds before it’s totally roasted.
      However, Weatherby didn’t build their rifles for that purpose. Few would shoot sub MOA for ten shots, and few weigh more than 10 pounds. They are intended as a lightweight hunting rifle that will drop the biggest game animals with authority. They are meant for gentlemen who would hardly shoot 500 shots through the rifle in a lifetime of hunting adventure, and to these goals, Weatherby is one of the finest rifles ever made.

      Fact is, “overbore” only really effects shooters. Problem may arise only when a hunter is also a shooter and uses a hunting rifle to shoot a lot with no regard for barrel life.
      I am a Tshirt wearing member of this club. I became infatuated with the 300Winchester Magnum some 10 years ago and scored a Remington 700 that shot exceptionally well printing about 1MOA with many cloverleafed 3 shot groups at 200 yards (which really blew my skirt up back then).
      Well, I don’t mind getting beat up by a rifle, and I treated that Remington like a freaking 22 and shot about 1200 rounds through it with totally reckless abandon. I remember distinctly the day accuracy flew south and never came back. Suddenly, I couldn’t keep all the shots inside 2″ at 200 yards. I didn’t understand why back then, and the Remington was put in the back of the safe.
      It wasn’t till years later I looked down the barrel with my bore scope and suddenly realized what I had done. That barrel was toast. I think it has about 6″ of gator checking and it will never shoot like it once did. Hubris of youth. If I had known about this subject, I would have been much more careful to preserve my barrel life and not waste it cutting down trees on the backstop etc etc.
      Live and learn.
      Point is, it’s worth tailoring your shooting habits to the cartridge you are working with, and if you have any of the cartridges listed in pink on Art’s list, you best put on your square wheels so things don’t roll along too fast.

    • #30319
      Waksupi
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      I look at performance as a standard. In relation to cast bullets, the .358 Win and .35 Whelen when used with cast bullets have the same velocity range for efficient accuracy. So why use the larger case? Nothing wrong with it, but we change the parameters when looking at the difference between cast and jacketed bullets.

    • #30322
      WCM
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      It is true, I use my Weatherby as a hunting rifle.
      I don’t mind if I have to shoot factory ammo in it, because three boxes of ammo will last me a few years.

      My target rifles are mostly .308 win’s

      When I have a target rifle built , it will probably be a .260 rem.

      I don’t particularly like the recoil of a .300 mag.
      It is fast and heavy.

      I still have a .300 and a .338

      They are special rifles I hand picked years ago. I doubt I will ever get to go on a hunting trip now.
      They will be passed on to my son when I am gone.

    • #30332
      Sgt. Mike
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      Ok just a theory gentlemen at the very end on reducing erosion with large capacity cases. I will base it on several laws of physics and known facts.This will support some of what CA Dude and I seem to think on erosion with large capacity slow burning powders .

      Burning takes place by parallel layers where the surface of the grain regresses, layer by layer, normal to the surface at every point – This law was devised by French General Guillaume Piobert in 1839 to explain the behavior of gunpowder, i will repeat this again

      The rate of burning of a propellant is also influenced by the initial temperature of the charge. The effect is much less than the normal effect on chemical reactions, but can still be important when the material is to be used over a wide range of temperatures from arctic to tropical and those encountered in supersonic flight. A characteristic of propellant burning is that it proceeds by layers with the burning front always parallel to the surface. This is known as Piobert’s Law, and it is on this law that the design of propellant grains depends. If, for example, we consider a long solid cylinder of propellant, then as burning proceeds the cylinder remains of the same shape but with gradually reducing radius. It is clear that the surface area of the propellant gradually decreases so that the mass rate of burning of the propellant also decreases.

      This is obviously undesirable and many means of avoiding it have been designed. One common method of designing propellant grains is to use a long annulus. This can burn on both the interior and exterior surfaces, so that as burning proceeds the outer surface decreases, but the inner surface increases in such a way that the total surface and therefore mass burning speed remains constant. For some purposes, it is indeed desirable that the rate of burning should increase during the process rather than remain constant. This is true in certain guns. For such purposes grains can be produced perforated by a number of holes so that the burning surface increases as combustion proceeds. While the shape of a propellant grain determines the constancy or otherwise of the burning process, the actual time occupied depends on the grain dimensions. The shortest distance in a grain through which burning can go to completion is known as the web thickness. In a solid cylinder this is for example the radius, or in the case of a plate half the thickness (the plate can, of course, burn from both sides). For a rifle propellant,which must burn very rapidly, the web thickness is small and may even be as little as one-hundredth of an inch. On the other hand, for the largest rockets with long periods of burning, the web thickness may be several feet.

      The actual process of burning of single and doublebase propellants has been studied in some detail and shown to consist of a number of stages The succession of stages is as follows.

      Solid propellant is first caused by radiation and convection to melt and evolve sufficient gas to give a foamy structure. This is known as the foam zone. The gaseous products from this zone pass through the fizz zone where an initial reaction occurs. These intermediate products enter the flame zone where after a brief induction period they undergo the final reaction to the combustion products. It is only in this final reaction that there is any luminosity, so that the fizz zone and the initial stages of the flame zone are in fact dark. The actual thickness of this dark zone depends on the pressure under which the propellant is burning. Below 200 lb/in2 the flame zone does not exist. When the pressure increases the dark zone decreases in thickness until at 1000 Ib/int it can no longer be observed. These changes explain well the marked dependence of burning rate on pressure.

      The burning mechanism of composite propellants differs from that described above. There is no exothermic reaction which can lead to a self-sustaining fizz zone. Instead, the first process appears to be the softening and breakdown of the organic binder/fuel which surrounds the ammonium perchlorate particles. Particles of propellant become detached and enter the flame. The binder is pyrolysed and the ammonium perchlorate broken down, initially to ammonia and perchloric acid. The main chemical reaction is thus in the gas phase, between the initial dissociation products.

      The stability of propellants from both the chemical and physical points of view is of considerable importance, because they frequently have to be stored for many years under adverse conditions of temperature. Minor changes, such as could well be tolerated with high explosives, cannot be allowed with propellants because they would seriously affect the performance of the gun or other weapon. Accelerated storage tests, usually involving cycling between the extremes of temperatures likely to be encountered, are used to determine the long term stability of products. In the case of large grains, such as those used in rockets, physical strength and stability can be of great importance. Thus it is usual to determine tensile strength and elongation under both static and dynamic conditions. Even more important is the examination of the grain for tendency to crack under conditions of varied temperature

      Many methods have been proposed and are used to study the thermal stability of propellants and to ensure the absence of possible autocatalysed decompositions during storage. None are sufficiently reliable to merit individual description. In practice, stabilizers are added, the usual being diphenylamine for nitrocellulose powders and symmetrical diethyl diphenyl urea (carbamate or centralite) for double base propellants. Provided a reasonable proportion of stabilizer remains, the propellant can be assumed to be free from the possibility of autocatalytic decomposition. The best test of stability is therefore a chemical determination of the stabilizer present.

      Ok now we understand how gunpower burns and react in the barrel we see that a by product of ammonia and perchloric acid is introduced to the barrel material as well as the coating element which can and do act as a abrasive during the dark zone.

      Herein starts the theory part of this .

      Now this action will cause erosion of the bore which is a effect caused by pulling the trigger and launching a bullet, bear in mind that the shoulder will act as a funnel, the neck will act as a shield to the chamber and leade and throat. Provided that the angle of the shoulder converges in the neck so the steeper the shoulder and longer neck will reduce this effect not negate the effect . In a cartridge that this does not occur it will converge within the leade, and / or throat area, with a over abundance of a slower burning fuel source this delays the pressure required for the flame zone which in essence consumes the ammonia and perchloric acid until the bullet is within it’s last little bit travel in the barrel ( hence huge muzzle flash). On the other side if we taper the shoulder and lengthen the throat we can place the convergence point beyond the throat and leade area thus avoiding flooding the leade/ throat area with ammonia and perchloric acid. Another method to reducing the effect of ammonia and perchloric acid is to get the flame zone to occur sooner in the barrel versus toward the end of the muzzle. By using slightly faster powder which in turn obtains higher pressure which induces the flame zone quicker. Another by product of this combustion of certain additives is nitrogen which will act to reduce the heat during this process occurring within the dark zone this can be altered with coatings of the powder mixture.

      Now that we have discussed why a barrel is shot or burned out we still have not defined overbore even though I have explained some of my thoughts on how to get large capacity to be gentler on the bore. Proper cleaning will and does go a long way to increasing bore life by removing the ammonia and perchloric acid that has not been consumed in the Flame zone. Another final thought is to lengthen the barrel as most will load to either a velocity, pressure signs, or certain accuracy level thus cutting back on the charge.

      Atlas I still cannot offer no definition of overbore

    • #30334
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      Mike,
      This explains the difference in muzzle flash experienced by so many water fowlers .
      I have shot a 26″ BPS for …..,um a while, and a 28″ O/U with a particular hand load the BPS showed around 18″ of dawn visible flash .(1 half hour before sun rise is pretty dark here). The O/U displayed less maybe only 14″ . (Casual eyeball measures)
      A close friend shoots factory ammo only and they must have used powders that barely made clean up pressures . The flame was daylight visible to about 3′.

      It is by coincidence the same reason that Unique and 4350 can have the same muzzle flash in a 308 , alibi at much higher velocities and pressures.

    • #30340
      Sgt. Mike
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      Speaking to to the issue of barrel erosion as most whom have replied as I do find themselves coming back to that effect when discussing this. I am wondering just how effective the melonite process would be to retard erosion. From what I have heard it will not enhance accuracy, some have claimed the opposite, most have claimed it retard throat erosion. The jury is still out on my opinion. I am thinking of trying that with a barrel just to see if it would actually retard the negative effect later, but I would not want to try it with a Broughton ,or Kreiger as it would really hurt my feeling to have accuracy go badly south on a quality barrel which cost more than say a green mountain.

    • #30341
      Rattlesnake Charlie
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      Sgt. Mike

      Deep. Good. Thorough. Thought provoking.

      My coffee cup is now empty.

    • #30345
      Sgt. Mike
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      Charlie last night I was discussing this (theory) with Goodsteel (Tim) and in a comparison of cases he made the comment of lack of pressure compared to another and stated pressure was simply not present.
      By getting wound up and attempting to push out my thoughts I disagreed, when later I reran our conversation through my head at which time. I was like why did I disagree? He was right in his statement even though I failed to show a good example that a straight walled case is less susceptible. Overthinking I suppose.
      We did not discuss melanite aspect that I alluded to in a earlier post per se.

    • #30348
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      The melanite process,based on my searching and sifting through a dozen descriptions of the process is more or less the same process as nitride treatment of aircraft cylinders. It has been used extensively more recently for wear resistance in automotive engine parts like cams and cranks . The short mechanics version is that it is a chemical cold case hardening system. The shooting industry reports ,barrel makers in the AR circles, that quality jobs by lot rival chrome lined for wear and longevity. In A/C cylinders it runs about 30% of ceramic and 40% of chrome with a life of 150% of steel . It lubricates and sheds heat better than chrome also .
      Apples and oranges. It takes 50-60 rounds to get the sand blast effect on the cases . A 6.8 AR I worked with took about 80 rounds to settle down to repeatable results with jackets . The cleaning was easy from the start . I likely wouldn’t have worn out the barrel in the allotted 10k rounds . My daughter was a Seabee Gunners mate and told me 556 in M4s would generally hold the 4″ with whatever lot of ammo they test fired to 18k in treated barrels while the OPS SS were all done around 12k. Take that at face value .
      I can tell you with certainty that the treatment vs plain steel in straight caliber matches makes more lead gas longer . Lapping shouldn’t be done nor like chrome can a chamber be changed after treatment. I think that covers all my knowledge advice and experience at this time .

    • #30354
      Sgt. Mike
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      Added after post #24

      Scharfschuetze,
      I would have thrown the 308 Win in here, but I did not find a 4831 load on Hodgden load data website. As I think it might have been another good bench mark to compare against. Powder burning efficiency of a common powder could very well be the answer.

    • #30355
      Sgt. Mike
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      Harter,
      your echoing what I understand as well. The machining, chambering would have to be done, and what I have heard is that it should be broke in fully, so depending on caliber 100-300 rounds. Then cleaned SPOTLESS every nook and cranny before being sent in and applying this process, otherwise it will fail.

      I recall something being said about certain SS barrels it not really being that effective on (alloy dependent, some took well) , and that Chrome Moly barrels is where it worked the best. the big down side I see is that barrel setback really can’t be performed. Which honestly if you extend the life by say 600-1200 rounds that is a little bit more than a set back is good for in a usual barrel burner setup. And would or might be cost effective.

      Of course those value are thrown out there for say target accuracy not hunt which certainly most hunters can buy a barrel burner without fear. As they are very unlikely to ever burn a barrel out even with the most barrel roaster available. Like Tim said it is only us shooters that are concerned with this.

      As I have one of the barrel burners, I have thought about this, because of my intended usage of this gun it would fit the bill to try, even if the accuracy went south a bit, just need minute of deer max prefer minute of Paraire Dog but hey, it all about fun.
      Question is do I stay 7mm bore or move a little bit smaller for this to a more supposedly aggressive burner?

      I appreciate everyone weighing in more than you all know on this topic even though we have shifted to the effect versus the condition. Which I really think is a natural state because in essence we are all kinda agreeing overbore is a ambiguous term, even though we all use it to describe a less than desirable condition.

      And I guess we should move on to the powder efficiency aspect as Scharfschuetze has pointed out which is I think is a viable thought.

    • #30361
      lar45
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      As long as we have some thread drift going here.
      Does anyone have any experience with Chryogenically freezing barrels?
      When I built my 30-378 I sent the barreled action to “300 Below” for their chryo treatment. My magazine box held 3 , vs Weatherby’s 2 . 🙂 The process involved taking the parts down to -300F for a couple of days, then slowly warming them up to room temp. It was a M1917 commercial 30-06 sporter when I started. Sorry no pics of it 🙁 They said that the process helped with the formation of ” tempered Martensite.”, and help stress relieve the steel. It was supposed to increase the wear life of steel by 3-4x that of untreated parts. I ended up selling it to fund christmas one year, so no long term use report to follow.

    • #30363
      Sgt. Mike
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      Glenn, Why yes I have shot Krieger barrels all of them are done ( Chryogenically frozen) before machining but they usually don’t advertise it although freely admit to doing it.

    • #30364
      Sgt. Mike
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      Here is a update I did a little calculating on two 6.5 mm Magnums against the 7mm Rem Mag and used a online source barrel life calculator done in excel the posted the results into a different spread sheet to see which was the worst barrel burner I used two powder type only that was common among the three cartridges I maxed the loads out per the load data offered by Hodgdon. Here are the results of that estimate…..

      CartridgeCase140 gr projectile
      H2O grsCC Volgrs H4831cc of H4831% FillvelocityEst Bbl Lifegrs H4350cc of H4350% FillvelocityEst Bbl Life
      6.5 Remington Mag684.4543.989%29431200493.681%27801256
      264 Winchester Mag825.3554.075%28531221523.871%28291146
      7mm Remington mag845.4644.685%29501233594.379%29271252

      Darn no clear winner to help make the choice easier. In case your wondering the 264 Win Mag and 7mm Rem mag had the lower pressures than the other 6.5 Mag

    • #30365
      Goodsteel
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      lar45;n10085 wrote: As long as we have some thread drift going here.
      Does anyone have any experience with Chryogenically freezing barrels?
      When I built my 30-378 I sent the barreled action to “300 Below” for their chryo treatment. My magazine box held 3 , vs Weatherby’s 2 . 🙂 The process involved taking the parts down to -300F for a couple of days, then slowly warming them up to room temp. It was a M1917 commercial 30-06 sporter when I started. Sorry no pics of it 🙁 They said that the process helped with the formation of ” tempered Martensite.”, and help stress relieve the steel. It was supposed to increase the wear life of steel by 3-4x that of untreated parts. I ended up selling it to fund christmas one year, so no long term use report to follow.

      Like Sarge says, Krieger cryo treats all their barrels and they do it correctly, (not all who claim cryo treating know what they are talking about as it is not simply a matter of swishing the steel in liquid nitrogen. There is a very controlled process to it).
      Yes, it improves many properties of the steel, but I think longer burnouts is not one of them, as I use Krieger barrels more than any other, and I can tell you they burn out pretty much on par with any other.
      Cryo treating is a great way to improve harmonic stability, and wear resistance (works extremely well on knife blades) but in a situation where you have a trifecta of heat, pressure, chemical, and physical erosion, there’s just not a whole lot you can do to resist that.

      One process that does effectively change the burnout numbers is Melonite conversion coating. It’s a beautiful smoke grey coating that is harder than carbide (ask me how I know) and combats throat erosion at it’s source, being naturally resistant to all the properties that a barrel combats. Blazer rifle’s use this finish (or something very similar to it) on their barrels, and I have to use diamond tooling to get through the crust in order to thread them.
      I once read a study on this which proved that this process extends barrel life significantly, but it was done by BR shooters, and the upshot of the study was that if barrel to barrel cost was the object, you’d be money ahead to just buy another barrel. I’m not sure I fully agree with that, because they were only counting the cost of the barrel and not the gunsmithing, but it would be close either way.

      That said, there’s a big difference between a target rifle that you know you will shoot out many times over in it’s lifespan, and a casual hunting/marksmanship rifle that 50% more barrel life could mean never having to replace the barrel again in your lifetime. This is certainly why Blazer does this, and I recommend it for people who are not trying to win matches.
      Melonite is the only effective means of extending barrel life that I have encountered, other than shooting cast bullets only.

    • #30369
      Sgt. Mike
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      Here is a update I did a little calculating on two 6.5 mm Magnums against the 7mm Rem Mag and used a online source for barrel life calculator done in excel then posted the results into a different spread sheet to see which was the worst barrel burner.
      I used two powder type only that was common among the three cartridges I maxed the loads out for a 140gr bullet per the load data offered by Hodgdon. Here are the results of that estimate…..

      CartridgeH2O grsCC Volgrs H4831cc of H4831% FillvelocityEst Bbl Lifegrs H4350cc of H4350% FillvelocityEst Bbl Life
      6.5 Remington Mag684.4543.989.00%29431200493.681.00%27801256
      264 Winchester Mag825.355475.00%28531221523.871.00%28291146
      7mm Remington mag845.4644.685.00%29501233594.379.00%29271252

      Darn no clear winner to help make the choice easier. In case your wondering the 264 Win Mag and 7mm Rem mag had the lower pressures than the other 6.5 Mag.

      Now what is it worth probably nothing,except as a guide. But according to the site that the calculator came from this was calculating SLOOW fire for target accuracy. So hunting accuracy should be about twice the estimated rounds. I don’t know how much stock to place in it but it is here for your use or disuse

    • #30372
      Rattlesnake Charlie
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      Are we considering all variables? Should we consider that a change in bore diameter include a change in bullet weight? Consider comparing a .357 mag and .44 mag in carbines. Apples to apples and oranges to oranges? I suspect there are a pear and a lime thrown in here. Comparing the same bullet weight in different bore diameters just seems to introduce additional variables.

      Too late for coffee. I’m sipping on some Jim Beam small batch.

    • #30377
      Sgt. Mike
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      Charlie I was looking to see for a barrel burner for a bolt face for a test with Melonite in post #27… Maybe ….. I was expecting to see the 6.5mm to burn quicker than a 7mm.

      But in the spirit of moving on I was crunching numbers while you was typing 😮 but remember these are estimates only…your mileage may vary…
      rate of fire is calculated at 1 shot per minute …………………….

      All data is at listed maximum do not use for load data.

      Barrel life is calculated for Target Shooting, for hunting estimated barrel life could/should double.

      Ok these are 30 calibers comparison the bullet is 150 gr weight first up is the original powder mentioned by Scharfschuetze 4831

      CartridgeCase cap H2OCase Cap CCH4831CC H4831% FiLLVelEst LifeVel per grVel per CCEfficiency VelEfficiency Life
      30-40 Krag583.76493.5594.5%2306417447.06649.12ControlControl
      30-06694.4761.54.4699.7%2800217645.53627.9896.7%52.13%
      300 H&H865.57785.66101.5%3313107842.47585.8590.3%25.83%
      300 Win Mag895.7775.55.4794.9%3055116540.46558.1286.0%27.91%
      300 Wby Mag996.42846.0994.9%327590338.99537.7782.8%21.63%
      30-378 Wby1308.421047.5489.5%355558934.18471.4972.6%14.11%

      Here is the same bullet in IMR 4064 you will see calibers dropped because no load data with hodgdon web site for that powder/caliber combo

      CartridgeCase cap H2OCase Cap CCIMR4064CC IMR4064% FiLLVelEst LifeVel per grVel per CCEfficiency VelEfficiency Life
      30-40 Krag583.76443.2887.2%2695503061.25822.15ControlControl
      30-06694.47513.8085.0%2928263357.41770.6393.7%52.35%
      300 H&H865.57644.7785.6%3170153949.53664.8580.9%30.60%
      300 Win Mag895.7765.54.8884.6%3205150448.93656.8079.9%29.90%
      300 Wby Mag996.42674.9977.8%3471147151.81695.3884.6%29.24%

      Again same bullet with IMR 4895

      CartridgeCase cap H2OCase Cap CCIMR4895CC IMR4895% FiLLVelEst LifeVel per grVel per CCEfficiency VelEfficiency Life
      30-40 Krag583.76362.6269.7%2435606867.64929.11ControlControl
      30-06694.47533.8686.3%3009196056.77779.8683.9%32.30%
      300 Win Mag895.7765.54.7782.7%3196116848.79670.2572.1%19.25%
      300 Wby Mag996.42664.8074.9%3214114548.70668.9172.0%18.87%

      Hopefully this more in line with what you was hoping for Gentlemen.
      For the efficiency Velocity percentages I was comparing the Vel per CC of the cartridge to the value of the 30-40 Krag. If one compares the Velocity per grain it should be the same but seeing how I attempted to show volume of fill I decided to use volume instead of weight of the charge.

    • #30378
      Goodsteel
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      Just a question: has anyone ever seen side by side test done with real barrels of identical make compared where one was fired regularly in a pure shooting scenario, and the other was shot only with a dead cold barrel (simulating a hunting scenario) and both pushed to burnout?

      I mean it’s one thing to measure barrel life in a full-auto scenario, and compare to that of a sporting rifle, (never mind the two could have different twist rates/loads/bullets/barrel lengths/barrel weights etc) ei= apples and oranges.

      Two or more identical barrels. Same ammo. Different shooting speeds. Who where and when was the test?

    • #30384
      Sgt. Mike
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      Ok even this was discussed as CA Dude and I went back and forth before I started this thread.
      What is barrel life?

      After two wall lockers being thrown across the room, six desk kicked over, terrorizing the building’s population to the degree that the Officer’s had to seek shelter from the fallout. This kinda happens when two opinionated Senior NCO civilly discuss matters they hold dear.
      We both came to the conclusion that the lack of standards across population of shooters expectation / definition prohibit a accurate / accepted definition of barrel life.
      Except for when the throat and bore are worn to the degree that the bullet goes sideways, or when expectations are not met.

      This is why the Civilian sector does not do tests as everyone could and would challenges the results. Where as DoD has a listed MOA acceptance area and establishes standards they adhere to within the testing disagreements are not allowed the results are the results any mention of what if is considered outside the parameters and is not entertained nor allowed.
      So however several shooters have attempted to do so over the years such as Mike Crawford in eastern NC he based his predictive spread sheet on Bart Bobbit and is continually refining based on input from a shooter base here is what Bart Bobbit said years ago:

      From: Bart Bobbitt
      Subject: Calculating Rifle Barrel Life

      I finally completed my research on a way to calculate how many rounds
      a rifle barrel can be expected to deliver its accuracy level. By that,
      I mean the barrel can be expected to have an average group size for
      so many rounds before that average group size starts to get larger.

      First, the rule-of-thumb formula I derived will produce a barrel accuracy
      life of about 3000 rounds.

      Second, if a lot of rapid fire (one shot every 5 to 10 seconds) is done,
      the accuracy life will be less.

      Third, if full-auto or very fast fire (a few shots per second, or one shot
      every second) is done, accuracy life will be much less.

      Fourth, the accuracy levels are for ranges through 600 yards. Once the
      barrel life calculated limit is reached, groups will probably start to
      get bigger at the longer ranges before they are noticeably bigger at the
      shorter ranges.

      My formula, or rule-of-thumb process, is:

      1. Calculate the bore area in square millimeters.

      2. Use one grain of powder for each square millimeter. This is what
      I call the reference, or base powder charge.

      Example: .30 caliber bore = 45.6 square millimeters.
      Base powder charge for .30 caliber is 45.6 grains.

      A .30 cal. cartridge that burns 45.6 grains of powder should give a
      barrel life of about 3000 rounds of good accuracy.

      3. If a larger cartridge is used and it burns more powder, the
      accuracy life in rounds for that bore size is reduced. The amount
      of reduction is determined by

      a. Divide the increased charge by the base charge, then square
      the answer.

      b. Divide that answer into 3000.

      Example: .28 caliber bore has a base charge of 38.5 grains.
      Cartridge burns 57.8 grains of powder.
      (57.8/38.5) squared is 2.25.
      3000 divided by 2.25 is 1,333 rounds.

      If anyone can shoot a hole through this theory, I welcome that shot. This
      is more or less an emperical process based on accurate barrel life in
      several calibers as reported to me by lots of folks. All I did was study
      the data and determine what math would give a best-fit formula.

      And if someone has a better method, I’d like to know what it is. My
      formulas may not be the best.

    • #30385
      Rattlesnake Charlie
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      Wow Sgt. Mike. A mathematical formula using a reasonable standard (3K round barrel life) with empirical data from actual records. Now we can make some accurate predictions of barrel life. If we accept the 3K round barrel life as the standard for normal bore, then anything resulting in less than 3K round barrel life becomes overbore. I can live with this.

      At the same time, I have no problem with those that demand increased performance from an overbore cartridge. They are willing to accept a shorter barrel life. As others have stated here, it may not be a problem for someone that will never shoot 1K through that barrel in the rest of their life. I never expect to burn out the barrel of my .375 H&H. My .223 varmint rifle on an AR, probably so if there are enough prairie dogs to please me.

      This has been a good thread.

    • #30386
      Rattlesnake Charlie
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      I decided to crunch the data for a .375 H&H mag.
      I selected a midweight bullet of 250 gr that produces about 2750 fps to make it comparable to the velocity and trajectory what is found in a .30-06 150 gr load.

      .375 inches = 9.525 mm

      Diameter of a 9.525 mm circle results in an area of 71.26 sq mm

      71.26 gr powder – Reference powder weight based on bore diameter
      83.0 gr powder – Hodgdon online manual max load for 250 gr bullet (this is the heaviest charge returned, and it is H4350)

      83.0 divided by 71.26 = 1.164748807184956

      3000 divided by 1.164748807184956 = 2575.66265060241

      2576 rounds till predicted burnout.
      I’m closing in on 63 years old.
      Not many grizzly bears or elephants in northern New Mexico.
      I think one of my sons will still enjoy shooting my rifle when they inherit it. Probably for the rest of their life.
      LOL!

    • #30388
      Sgt. Mike
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      Charlie that e-mail text from Bart Bobbit dates to prior the Internet as we know it today, it was posted on a usernet group years ago. Websites was only in the imagination when that was penned.

      While I sound aggressive I truly am not attempting to be so. But unless a true definition exist for overbore then there is no such thing as overbore, that is what CA Dude I concluded before I even posted this. We got to that conclusion in less than 3 hrs and continually do a redress to ensure we didn’t miss something but we do agree that most usage of the term is slander against a cartridge.

      For the past few posts we have been addressing erosion within the throat and loss of accuracy not overbore but rather the effects. Which may be a good way to sorta nail it down but with this small base I doubt such a occurrence will happen.

      The spreadsheets that I did was based on Mike Crawford’s calculation’s for predictive barrel life his base product was done off what Bart Bobbit stated which are usually updated as new data is done. (btw if you want to read a more up to date post of his go here http://www.thehighroad.org/archive/i…/t-786330.html his user name is Bart B.)
      If I knew how to attach the spreadsheet that Mike Crawford did up onto the forum here I would (pm me I guess with a e-mail I could share to those that are interested). The problem with updated files is that it leaves many different versions out there. I don’t know how many version he has gone through, but I have seen over 5 noticeable ones thus far. On what I did I used Scharf’s request to use 4831 to pick the cartridges why did I pick 30-40 Krag one I had load data and information to do predictive life and it had the highest barrel life and it was not listed in the other index that Art posted as slightly overbore or overbore. That is the reason I did shift powder to show that different powders would produce different results.

      For the data input for the excel file is:
      1. dia of the bullet
      2. powder load
      3. powder heat potential ( there is a comment block to look up the KJ/Kg heat index for your powder)
      4. Pressure in pounds per sq in ( hey my data is in CUP yeah not the same, without a pressure gun I guess you need to use a formula to do a correlation see here https://www.shootingsoftware.com/ftp/psicuparticle2.pdf it is a 98% with only 2% error, it is well worth what you paid for it)
      5. in the later versions there is a modifier for moly coated and melonite. moly gives 18% increase for those of us that don’t agree with moly extending the life simply don’t feed a value in there and it calculates naked bullets. Although MikeCr (as he is known of several different forums) has started the Melonite adjustment in the spreadsheet he does not have it functional in the last one I have, as he did not have enough data to add it yet or even know if it really helps.

      Now some will complain about twist, bullet weight, velocity sorry in the calculations it is covered under pressure.

      ( here is a link to a site back in 2013 that a conversation about this cause and effect was taking place Bart Bobbit and Mike Crawford are interacting on longrange hunting forum and Mike Cr gives his e-mail address if someone might be interested http://www.longrangehunting.com/foru…l-life-119069/ )

      I don’t think anybody can honest say when barrel life will shorten as too many variables. And many different versions of what is useable barrel life is which is flat disheartening for a Gunsmith or Gun Dealer but at least if worded correctly will guide the client. “I have seen target grade accuracy go in as little as 2500 round to as many as 5000 rounds if you take care of the barrel and don’t abuse it”. Probably would be the Gunsmith’s best honest advice.

      On your 375 H&H Charlie I would double to triple the number for hunting usefulness so honestly I really don’t think you will have a problem outside the 30-378 weatherby mag

    • #30394
      Sgt. Mike
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      I just feel the need to say this though your accuracy loss is a gradual thing which makes it hard to actually determine for the hunter. it does not just go to pot when you hit a certain number of rounds rather it is a gradual thing. kinda like aging …..shoot I just can’t run that far anymore. But I will say if you leave a cleaning rod in the bore and shoot, it does immediately go to pot (ask me how I know :rolleyes: and no that is not picking on anyone but me).

      While this has been a long thread I am in hopes that it has been:
      a. thought provoking
      b. helpful to a degree / informative
      c. fun
      d. humorous at times with quirks being said

      Again everyone whom has or has not responded thank you for your time, and attention.
      Especially for your patience for being civil and open minded.
      In closing this post (not the thread) while I feel that overbore has no purpose as a term. I will appreciate and understand those that use the term without pointing back to this thread, as they are just attempting a negative comment about a cartridge or rifle without just saying so.

      Accurate Barrel Life
      Bullet Dia [in]0.308
      Loaded Powder [gr]36
      Powder Heat # [from comment]4080
      Pressure [Psi]39,70039700
      Shot Rate [Sec]608 Std
      Extending Adj [%]0100%
      Total6068

      just for giggles this a screen shot of the Spreadsheet I mentioned earlier is it the cat’s meow I dont know but I think it is a good as anything else

    • #30406
      CA Dude
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      SGT Mike, you know very well it was only two desks. At lest the “O” had the sense to leave the office. I think an increase of one MOA for a target rifle is a reasonable standard to determine a barrel life cycle. Shooting minute of angle is much more difficult than shoot minute of deer. Our standard cartridges today are all a “little” over bored if we look at the charts. We like to drive fast cartridges for the same reason we like to drive fast cars. Driving a 65 Mustang is cool, driving a 65 Rambler, not so much. Shooting the 26 Nosler, at lest according to the firearm magazines is cool. Shooting the 6.5×55 Swede, not so much. Strange thing is the 6.5×55 Swede is 122 years old and according to the charts is over bored but I never heard it called a barrel burner. The 26 Nosler is what three years old and it’s over bored but I think we could agree that it is a barrel burner. No one cares that it is over bored because it’s cool. We all want to be cool. Isn’t that why you driver a new Dodge Charger?

    • #30435
      Sgt. Mike
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      I finally researched my history and found the link to the 2013 version ( Ithink it’s the most recent version) http://accurateshooter.net/Blog/barrellife2013oct.xls

    • #30477
      Sgt. Mike
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      JWT,
      CA Dude and I was discussing me doing this with a Remington 700 – 7mm Mag that I have that is about shot out. Tim and I discussed this today at his house the added length in neck is along the line of the 6.5-06 and the 6.5×57 M-S.

      Look at the notes that I posted on the reamer drawing should be easy to do when ordering. My thoughts are this should keep the convergence point inside the neck in hopes of extending useful life.

      For brass source my thoughts was .264 Win as it would be the easiest to form from it’s 2.5″ length. now to locate dies.
      Ballistic ally looking in the 7mm Rem Mag versus the 6.5 Rem mag the 7mm takes about 60-61 grs for a 2785 fps load in IMR 4350 with a 140 gr bullet.
      I can get equal or better velocity the same weight bullet with 44-46 grs of the same powder. The estimates are a 800 to 1000 rounds longer life. Lengthening the throat might add even more. Only one way to tell for sure.

      The fact that this is dead cartridge is a mixed blessing.

    • #30478
      CA Dude
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      SGT Mike I think this is the way to go.

    • #30479
      Sgt. Mike
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      Ed you should have been at Tim’s Yesterday I brought the 7mm Mag out to re-zero so Mike my son can take it to the deer woods this year. Jason was there and kinda challenged me to shoot his steel targets ( @100 yds) yeah the 7 mag almost busted completely through the 3/8″ steel. I just giggled the load was Remington 140grs flat base bullets over 60 grs of IMR 4350 netted 2785fps. Grouping was not bad 2 to 21/2″ at 100, if that rifle responds like all the old 7 Mags I loaded for in the past at about 1 gr off max is where she will tighten up. (add one more grain max is listed at 62.5grs)
      then picked up the Magno speed that Bjorn was kind enough to let me use for a bit.

      Changing the subject back to the thread I wanted to go dead at .400 plus in the neck, but figured at 25 degrees versus the ought six’s 17 degree shoulder that if I went with that length or the 6.5x57mm M-S neck length that it would work. Without a un seemingly long neck that would look odd for that short mag. I’ll take you up on the .264 Win brass soon as I get the dies, I can then set up a base (dummy) cartridge for either Mason or PTG with a drawing to do a reamer. this should not require a new custom dies as the neck in the dies are straight through and don’t have a obstruction such as the chamber will have. So regular 6.5 Rem Mag dies will work.

      added at 1221 hours, 3 October
      The more I think about it after our conversation in your office Ed I think I’ll go +.070 of a inch. Then just keep the taper in the neck as originally drawn, but reduce diameter to .300 then taper to .298. Which as you pointed out will aide in extraction, yet offer a tighter neck. Last but not least do the 1 degree 30 second throat ( just partial to that degree throat, really don’t know if it would be a advantage over the 3 degree).

      Shilen is currently not offering the exact contour I’m envisioning in a finished length of 26 inch. I could go 30 inch and get the Palma contour which I kind of lean towards, although the Varmint is nothing to sneeze at, it’s just a little bit heavier than the Palma by a few pounds. Looking at 1-8 twist to shoot the Sierria 140 gr match bullets as well as the Bergers.

    • #32444
      Sgt. Mike
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      Here is a calculation that incorporates Quickload and the spreadsheet for barrel life that I did for the 6.5 remington mag using 142gr SMk and normally used powders for that cartridge.
      kJ/kg is the heat or energy potential of the selected powder.

      Cartridge : 6.5 mm Rem. Mag.
      Bullet : .264, 142, Sierra HPBT Match King 1742 G7 Litz
      Useable Case Capaci: 58.313 grain H2O = 3.786 cm³
      Cartridge O.A.L. L6: 2.806 inch = 71.27 mm
      Barrel Length : 30.0 inch = 762.0 mm
      Predicted Data for Indicated Charges of the Following Powders.
      Matching Pressure: 55204 psi, or 380 Mpa to max 61000 psi, or 420 Mpa
      or a maximum loading ratio or filling of 100 %
      These calculations refer to your specified settings in QuickLOAD ‘Cartridge Dimensions’ window.
      C A U T I O N : any load listed can result in a powder charge that falls below minimum suggested
      loads or exceeds maximum suggested loads as presented in current handloading manuals. Understand
      that all of the listed powders can be unsuitable for the given combination of cartridge, bullet
      and gun. Actual load order can vary, depending upon lot-to-lot powder and component variations.
      USE ONLY FOR COMPARISON !
      79 loads produced a Loading Ratio below user-defined minimum of 65%. These powders have been skipped.
      Powder type Filling/Load RatioCharge Charge Vel. Prop.BurntP maxP muzzB_TimekJ/kg Heat energy potAccurate BBL Life
      %GrainsGrammfps%psipsims
      ——————————— —————————————————————–
      IMR 489580.243.12.792912100.055,20478051.46340801643
      IMR 489583.344.82.902995100.061,00079831.400! Near Maximum !40801376
      Hodgdon H4895 78.142.02.722885100.055,20475461.46340601774
      Hodgdon H4895 81.343.72.832967100.061,00077281.401! Near Maximum !40601483
      Alliant Reloder-2297.452.93.43304299.955,20494381.440! Near Maximum !39901220
      Alliant Reloder-22 100.054.33.523117100.061,00095481.387! Near Maximum !39901047
      Alliant Reloder-1994.250.63.28299499.855,20489841.439! Near Maximum !39801350
      Alliant Reloder-1997.352.33.393081100.061,00091341.378! Near Maximum !39801143
      Hodgdon H38082.545.32.942911100.055,20479251.46639701705
      Hodgdon H38085.547.03.042993100.061,00080801.403! Near Maximum !39701434
      Ramshot Hunter89.849.93.232981100.055,20485961.44739101517
      Ramshot Hunter92.951.63.343065100.061,00087351.386! Near Maximum !39101284
      IMR 432083.043.92.842891100.055,20475271.44838902010
      IMR 432086.145.52.952971100.061,00076891.388! Near Maximum !38901694
      Accurate MAGPRO 97.755.83.62306398.455,20499921.44038801260
      Accurate MAGPRO 100.057.13.70313899.059,946101521.388! Near Maximum !38801109
      Hodgdon H414 84.848.23.122979100.055,20486191.44938801689
      Hodgdon H414 97.749.93.233065100.061,00087551.387! Near Maximum !38801426
      IMR 406484.242.82.772867100.055,20473891.45838802143
      IMR 406487.544.42.882948100.061,00075551.396! Near Maximum !38801802
      Winchester 76084.848.23.122979100.055,20486191.44938801689
      Winchester 76087.749.93.233065100.061,00087551.387! Near Maximum !38801426
      Hodgdon H4831 SC95.652.03.37297398.955,204889521.43838701470
      Hodgdon H4831 SC98.653.63.47306199.561,00091301.376! Near Maximum !38701252
      IMR 7828100.052.23.38300999.252,36994531.45538501578
      IMR 7828 SSC96.153.13.44305699.555,20495441.42138501447
      IMR 7828 SSC99.054.73.54314599.961,00096831.360! Near Maximum !38501234
      Accurate 435088.747.73.092949100.055,20481731.47737901940
      Accurate 435091.649.23.193029100.061,00082971.413! Near Maximum !37901650
      Hodgdon H435091.748.23.122925100.055,204821291.44837601977
      Hodgdon H4350 95.049.93.243010100.061,00083571.386! Near Maximum !37601669
      IMR 435090.048.13.122923100.055,20481971.44837601985
      IMR 435093.249.83.233009100.061,00083351.386! Near Maximum !37601676
      IMR 483193.748.23.132934100.055,20480251.46837202085
      IMR 483197.049.93.233014100.061,00081601.405! Near Maximum !37201761
      Accurate 2700 84.847.53.082857100.055,20476711.46535452732
      Accurate 2700 87.849.23.192941100.061,00077991.402! Near Maximum !35452305

    • #32452
      jwt
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      I wonder if that barrel life difference between 4895 and 4064 holds true for the 308 and 30-06. For the same pressure there is a 30% increase in barrel life.

    • #32472
      Sgt. Mike
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      JWT
      a 30 caliber running IMR 4895 at 47.5gr (55,000 psi) will net approx 2516 rounds before slipping into the next ring.
      the same 30 caliber with IMR 4064 47.8 (55,500 psi) 3165 rounds before again slipping into the next ring.
      The 7.62 mm NATO will net a higher count with IMR 4895 at 42.5 grs will be 3143 before slipping to the next ring. With IMR 4064 at 43 grs rounds count goes to 3911.
      Why? simple we are not running these to the max pressure which causes more erosion, the more grains of powder the more erosion, the higher the kJ/kg factor the higher heat potentional again more erosion. The factors are:
      a. Heat/ energy potential of the powder (kJ/kg)
      b. amount of powder
      c. pressure generated
      d. rate of fire.

      note I said accuracy slips to the next ring I did not say it (the barrel) was shot out. In the table above I used the 6.5 Remington mag at FULL pressure of the brass, then compared to 10,000 reduction.
      Pressure = Velocity pure and simple.

      if one was to say use the 30 caliber at full potential in say IMR 4895 53 grs that 2516 for 47.5grs drops to 1916 for the increased charged, what has changed is the amount of powder and pressure not the heat potential of the powder.

      http://accurateshooter.net/Blog/barrellife2013oct.xls

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