- July 14, 2016 at 6:29 pm #28900
I have the basics. Every bullet is a shuttle cock except WC and HBWC, and if you blow the skirt it is too. What I mean is they’re wider at the back or some point past center than at the front . That helps keep the front forward and the back ……. um …..Back . With an appropriate amount of spin applied around a center line the projectile is more resistant to getting the front out the side . Like all good things it is best in moderation not enough and even a RB will wander and in the extreme the projectile can fling itself apart with too much .
I’m aware of center of pressure , lift and gravity and that they are different things . Lift and vertical spin are on a short list of things that we can ignore I think.
I’ve read many treatise on assorted forums and in many cases find that half of what we see as essential bullet shape is cosmetic at best until the bullet reaches some terminal point in its flight ,typically, way beyond Joe shooters useful range sometimes beyond any useful range ……. except possibly large caliber artillery that actually shoots over the earth’s curve and aiming actually is dependent on leading a stationery target .
For this exercise I would like stick to conical shapes for pistol application preferably suited to the carbine trouble makers of 35,44,45 cal as it relates to RN, TC and acorn like or potentially a double ended SWC (for description only ) within normal weight/length for caliber .
I’m struggling with several bullets that are well within twist per length and outside of the transonic abuses. So say the balistic calculators and flight relieve to sights over flat ground . This leaves me with few possible answers for the erratic bullet flight . The bullets ARE destabilizing and it IS twist related……..maybe . I am not yet brazen enough to send a 265 gr chunk of lead over my Chrony at 70 yd and 10 ft to confirm a calculator. When a load shoots at 25,50 and 75 but goes over the berm at 100 spreading out from paper plate to rail car then I feel safe discounting the shooter and gun .
Don’t shoot past past 234 ft .
Shoot faster loads …… pretty much at the top now but maybe a different powder…..
Get a bullet that will beat the aerodynamics to either stay above TS or reduce its effects to 110 yd.
What attributes does a short fat bullet need to beat the wind ?
Ideally it would be 2 calibers long and have a full caliber drive length.
There hasn’t been enough work to make a call on a rebated base with cast so let’s toss that .
That leaves a 2 radius nose into the front band or a 3 radius RN again into front band .
But only if it’s worth the effort for a slicker bullet.
At this point I’m rambling from physical knowledge and proofed demonstrated data that I actually can see and touch but not describe in any reasonable way to someone not looking at what I’m seeing.
- July 15, 2016 at 2:12 am #28901chutesnreloadsParticipant
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I’ve noticed this too with larger slower projectiles…..Could it simply be the longer time of flight allows the natural events of the earth (even a slight breeze)to have a greater affect on the said projectile?Also noticed it with pellets from air rifles at extended ranges….a tack driver to a certain point and then the pellets just start doing odd things
- July 15, 2016 at 1:15 pm #28904
Harter, I’m digging the hell out of the topic, but you’re missing some very specific information.
May I propose we briefly address each rifle, one at a time, starting with the 357 and working up to the 45, then we put it all together?
The things I want to know for each given rifle are:
1. What is your measured twist rate for this specific rifle?
Measuring twist rate with a cleaning rod is a crap chute. The only way to get it done perfectly is to use a jag that will not twist in the patch, and a rod that will not twist in the jag. Also a very tight patch. If this is not done, I don’t trust the readings. Wright Arms followed my advice, and found his readings were off. Personally, I precisely measure twist rate optically with my Hawkeye bore scope, but few have that option.
2. I want to know exactly what bullet/bullets you are using in each firearm.
3. I want to know what the chronograph readings are.
Generalities are born from specifics. Not the other way around. The evidence doesn’t lie, but our interpretation can be way off and all it takes is a couple assumptions.
What say you?
- July 15, 2016 at 3:27 pm #28905
Unless I get some wild hair the 35 cal WC is off the bench besides it’d look silly in a 358 Win.
So that drags me back kicking and to the Rosschester Colts . They are advised as 1-30 and common consensus offers validation. While unscientific the 20 inch is by eye ,just short of 2/3 of a turn from muzzle to chamber which has been discovered to be very long in the 16″ sister rifle which eyeballs at an honest half turn muzzle to chamber . With that discovery bullet damage is also on the table as a culprit and begs me to do a similar case fit in the 20″ rifle as well .
The irony would be in that it is possible that the consistency failure might just go away with proper case length . However that doesn’t make this an unworthy wonder.
My box data states that the loads worked are ;
CCI 250 primer
454424 at .454 and 258 gr
Chrony says 1325@10 ft
Trajectory failures occurredat 72-80 yd.
CCI 200 primer
9.5 Unique (1968 lot it runs fast in every load.)
452-252 SWC Lee (this mould has a new home )
.454 262 gr
It clocked 1050 +- 15 in the 7.5 Blackhawk and 1175-1225 from the 16″ . Definitely in the transonic tunnel and printed sideways on a 45 yd target .
Other loads loads of note include
452 255RNFP Lee over Unique at 1285-1325 @265 gr
a paper patched 429426 at .448 and 257 gr @1315-1327 over H110 and 1275-1310 over Unique.
All loads from the 16″.
All loads become consistently wild between 75-80 yd except as noted.
This is box data derived from work ups and may or may not represent a given lot of bullets, alloy primer or what a charge weighs if I were to pull it today.
As an associatednote the failure does occur also in loads with all of the bullets listedthat are loaded over 8.0 Unique for an MV of 1025-1075 with ovals showing at 90-100 yd and the 452 252 the worst offender .
All of this screams at me marginal twist and ” hey don’t shoot in the transonic window stupid . ” The trouble is getting far enough above super to stay there to the arbitrary 110 yd or getting a heavy to stabilize and deliver from below sonic. Without creating a new bullet shaped like the little pointy 115 gr sks bullet and scaled up to 45 I don’t see beating the wind as an option .
Why is the no Money bullet of under 300 gr ?
- July 15, 2016 at 3:49 pm #28906popperParticipant
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don’t shoot in the transonic window stupid Harter, I’m sure you are aware that deceleration increases with range. Spin doesn’t change much so gyro effect doesn’t change much either. Our stability is a balance (?) between spin and aero effects. NASA has data on various projectile shapes showing the ‘trans-sonic’ velocity range is much wider than we think (dynamic – ~30% +/-). Over spin (RPMT) can cause problems with static balance, but it also crates more precession force. Aero effect overtakes spin effect and – bad results. Heavier boolits have more forward momentum so the imbalance has a lesser ‘effect’. Hope that helps.
- July 15, 2016 at 7:53 pm #28907
I agree with popper.
The loads and rifle you describe are altogether putting you in a real pickle for which there is no answer.
Basically you’re using a rifle that was designed for general farm use, putting holes in things that need shot out to 50 yards. That was the purpose of the rifles.
You’re trying to take the rifle outside it’s intended parameters. Nothing wrong with that at all, but no matter what you read on the WWW, anybody who really shoots these rifles at anything but rocks, finds themselves in the same quandary you have.
You say it’s a slow twist and I know that’s probably correct because I’ve seen enough of them, but I still wish you could take us out of “I read somewhere” and into “I measured it and this is what the facts are”.
You say it’s a 1-30. Fair enough. Sounds like a 230gr RN was the intended bullet and it was supposed to be going about 900FPS. Well below transonic.
My thought would be to shoot the shortest RN bullet you think you can get away with, and shoot it just under transonic. Try it at 1000FPS.
Do not use any type of a FN bullet.
Do not cross 1100FPS
This is one you’re going to have to use finesse to get those bullets out to 100 yards.
Too bad the schtoopid dumbcuffs didn’t see fit to put a decent twist rate on those rifles. They pretty much made it a 50 yard gun no matter what.
- July 16, 2016 at 1:18 am #28908
Mauser in 450 Raptor with a 16 or 18 twist and run it like a 45 60 straight is next up then .
For those not knowing it is 460 S&W rimless, a 1.9 inch 308 case at 451 groove.
All the issues go away .
Off to the the experimental bullets drill press ..
- July 16, 2016 at 1:51 pm #28912Butch WaxParticipant
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Perhaps I’m just a might too old school, but with the 1:30 twist a short bullet goes better. Instead of going all out high tech and all, have you tried a 180gr or 200gr? No offense, but its my belief you’re overthinking this. I don’t know transgender subsonic hypertension speed stuff, but I understand rifling. When I built muzzle loader rifles for roundball they had a 1:66 bore. 30’06 bolt guns had 1:10. Check the levergun forum of this site. There you’ll find a thread involving my Rossi R92 in 357mag that refused to work with longer bullets but became a near tack driver at 100yds with shorter bullets. It ain’t rocket science but it is pure physics.
A suggestion from an old man…. Go to Badman Bullets and buy one of their sample packs of 25 in .452″ for a 180gr and one for the 200gr. I think their sample packs are $8.95 shipping included. For less than the price of a meal at Chillys or Applebys you can give this a try and not have to buy any more moulds for this particular testing. That is, unless one of those short bullets works of course. Then your can go get a similar size later, huh? Of you can disregard the advice of an old man and build exotic rounds that will do the same thing unless you rebarrel to a faster twist that is. Ok. That’s all I’m gonna say here. Your choice, your weapons here. Have fun!:)
- July 16, 2016 at 2:21 pm #28913popperParticipant
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Harter – apologies, didn’t intend to say you’re stupid, just as GS says, out of design parameters. Let me rephrase the NASA data statement. NASA projectile data for the normal type ogive we use perform poorly well above and below the S.O.S., just staying below SOS doesn’t mean it works well. Actually, a modified TC works very well at slower speed and obviously shorter range.
- July 16, 2016 at 2:58 pm #28914
No worries fellows I got pretty thick skin . The transonic foolishnesswas my remark anyway.
I do have a 45-200 RCBS SWC and a box of commercial 230 RN with probably 3-400 left i.
- August 10, 2016 at 4:30 pm #29365
Bullet stability hum good topic , in order to have accuracy the bullet must be stable.
To help some that may not be right up with the idea I’ll post a article or several from accurate shooter. com
26th August 2016: Twist Rate: Common Misconceptions about Twist and Stabilization
Understanding Twist: Bullet Stabilization
by Sierra Bullets Ballistic Technician Paul Box for Sierra Bullets Blog.
Based on the questions we get on a daily basis on our 800 (Customer Support) line, twist is one of the most misunderstood subjects in the gun field. So let’s look deeper into this mystery and get a better understanding of what twist really means.
When you see the term 1:14â€³ (1-14) or 1:9â€³ twist, just exactly what does this mean? A rifle having a 1:14â€³ twist means the bullet will rotate one complete revolution every fourteen inches of the barrel. Naturally a 1:9â€³ turns one time every nine inches that it travels down the barrel. Now, here’s something that some people have trouble with. I’ve had calls from shooters thinking that a 1:14â€³ twist was faster than a 1:9â€³ because the number was higher with the 1:14â€³. The easiest way to remember this is the higher the number, the slower the twist rate is.
Now, the biggest misconception is that if a shooter has a .223 with a 1:8â€³ twist, his rifle won’t stabilize a 55gr bullet or anything lighter. So let’s look at what is required. The longer a bullet is for its diameter, the faster the twist has to be to stabilize it. In the case of the .223 with a 1:8â€³ twist, this was designed to stabilize 80gr bullets in this diameter. In truth the opposite is true. A 1:8â€³ will spin a 55gr faster than what is required in order to stabilize that length of bullet. If you have a bullet with good concentricity in its jacket, over-spinning it will not [normally] hurt its accuracy potential. [Editor’s Note: In addition, the faster twist rate will not, normally, decrease velocity significantly. That’s been confirmed by testing done by Bryan Litz’s Applied Ballistics Labs. There may be some minor speed loss.]
Many barrel-makers mark the twist rate and bore dimensions on their barrel blanks.
Think of it like tires on your truck. If you have a new set of tires put on your truck, and they balance them proper at the tire shop, you can drive down a street in town at 35 MPH and they spin perfect. You can get out on the highway and drive 65 MPH and they still spin perfect. A bullet acts the same way.
Once I loaded some 35gr HP bullets in a 22-250 Ackley with a 1:8â€³ twist. After putting three shots down range, the average velocity was 4584 FPS with an RPM level of 412,560. The group measured .750â€³ at 100 yards. This is a clear example that it is hard to over-stabilize a good bullet. Twist-rate illustration by Erik Dahlberg courtesy FireArmsID.com. Krieger barrel photo courtesy GS Arizona.
On June 3rd, 2008 Calculating Bullet RPM — Spin Rates and Stability
Most serious shooters can tell you the muzzle velocity (MV) of their ammunition, based on measurements taken with a chronograph, or listed from a manufacturer’s data sheet. (Of course, actual speed tests conducted with YOUR gun will be more reliable.)
Bullet RPM = MV X 720/Twist Rate (in inches)
Photo by Werner Mehl, http://www.kurzzeit.com, all rights reserved.
However, if you ask a typical reloader for the rotational rate of his bullet, in revolutions per minute (RPM), chances are he can’t give you an answer. Knowing the true spin rate or RPM of your bullets is very important. First, spin rate, or RPM, will dramatically affect the performance of a bullet on a game animal. Ask any varminter and he’ll tell you that ultra-high RPM produces more dramatic hits with more “varmint hang time”. Second, RPM is important for bullet integrity. If you spin your bullets too fast, this heats up the jackets and also increases the centrifugal force acting on the jacket, pulling it outward. The combination of heat, friction, and centrifugal force can cause jacket failure and bullet “blow-ups” if you spin your bullets too fast.
Accuracy and RPM
Additionally, bullet RPM is very important for accuracy. Nearly all modern rifles use spin-stablized bullets. The barrel’s rifling imparts spin to the bullet as it passes through the bore. This rotation stablizes the bullet in flight. Different bullets need different spin rates to perform optimally. Generally speaking, among bullets of the same caliber, longer bullets need more RPM to stabilize than do shorter bullets-often a lot more RPM.
It is generally believed that, for match bullets, best accuracy is achieved at the minimal spin rates that will fully stabilize the particular bullet at the distances where the bullet must perform. That’s why short-range 6PPC benchrest shooters use relatively slow twist rates, such as 1:14â€³, to stabilize their short, flatbase bullets. They could use “fast” twist rates such as 1:8â€³, but this delivers more bullet RPM than necessary. Match results have demonstrated conclusively that the slower twist rates produce better accuracy with these bullets.
Calculating Bullet RPM from MV and Twist Rate
The lesson here is that you want to use the optimal RPM for each bullet type. So how do you calculate that? Bullet RPM is a function of two factors, barrel twist rate and velocity through the bore. With a given rifling twist rate, the quicker the bullet passes through the rifling, the faster it will be spinning when it leaves the muzzle. To a certain extent, then, if you speed up the bullet, you can use a slower twist rate, and still end up with enough RPM to stabilize the bullet. But you have to know how to calculate RPM so you can maintain sufficient revs.
Bullet RPM Formula
Here is a simple formula for calculating bullet RPM:
MV x (12/twist rate in inches) x 60 = Bullet RPM
Quick Version: MV X 720/Twist Rate = RPM
Example One: In a 1:12â€³ twist barrel the bullet will make one complete revolution for every 12â€³ (or 1 foot) it travels through the bore. This makes the RPM calculation very easy. With a velocity of 3000 feet per second (FPS), in a 1:12â€³ twist barrel, the bullet will spin 3000 revolutions per SECOND (because it is traveling exactly one foot, and thereby making one complete revolution, in 1/3000 of a second). To convert to RPM, simply multiply by 60 since there are 60 seconds in a minute. Thus, at 3000 FPS, a bullet will be spinning at 3000 x 60, or 180,000 RPM, when it leaves the barrel.
Example Two: What about a faster twist rate, say a 1:8â€³ twist? We know the bullet will be spinning faster than in Example One, but how much faster? Using the formula, this is simple to calculate. Assuming the same MV of 3000 FPS, the bullet makes 12/8 or 1.5 revolutions for each 12â€³ or one foot it travels in the bore. Accordingly, the RPM is 3000 x (12/8) x 60, or 270,000 RPM.
Implications for Gun Builders and Reloaders
Calculating the RPM based on twist rate and MV gives us some very important information. Number one, we can tailor the load to decrease velocity just enough to avoid jacket failure and bullet blow-up at excessive RPMs. Number two, knowing how to find bullet RPM helps us compare barrels of different twist rates. Once we find that a bullet is stable at a given RPM, that gives us a “target” to meet or exceed in other barrels with a different twist rate. Although there are other important factors to consider, if you speed up the bullet (i.e. increase MV), you MAY be able to run a slower twist-rate barrel, so long as you maintain the requisite RPM for stabilization and other factors contributing to Gyroscopic Stability are present. In fact, you may need somewhat MORE RPM as you increase velocity, because more speed puts more pressure, a destabilizing force, on the nose of the bullet. You need to compensate for that destabilizing force with somewhat more RPM. But, as a general rule, if you increase velocity you CAN decrease twist rate. What’s the benefit? The slower twist-rate barrel may, potentially, be more accurate. And barrel heat and friction may be reduced somewhat.
Just remember that as you reduce twist rate you need to increase velocity, and you may need somewhat MORE RPM than before. (As velocities climb, destabilizing forces increase somewhat, RPM being equal.) There is a formula by Don Miller that can help you calculate how much you can slow down the twist rate as you increase velocity.
That said, we note that bullet-makers provide a recommended twist rate for their bullets. This is the “safe bet” to achieve stabilization with that bullet, and it may also indicate the twist rate at which the bullet shoots best. Though the RPM number alone does not assure gyroscopic stability, an RPM-based calculation can be very useful. We’ve seen real world examples where a bullet that needs an 8-twist barrel at 2800 FPS MV, would stabilize in a 9-twist barrel at 3200 FPS MV. Consider these examples.
MV = 2800 FPS
8-Twist RPM = 2800 x (12/8) x 60 = 252,000 RPM
MV = 3200 FPS
9-Twist RPM = 3200 x (12/9) x 60 = 256,000 RPM
Of course max velocity will be limited by case capacity and pressure. You can’t switch to a slower twist-rate barrel and maintain RPM if you’ve already maxed out your MV. But the Miller Formula can help you select an optimal twist rate if you’re thinking of running the same bullet in a larger case with more potential velocity.
On October 1st, 2015 The Transonic Zone — What Happens to Bullet Stability and BC
These four photos show the substantial changes in the shock wave and turbulence patterns for the same 7.5mm bullet at different velocities. The “M” stands for Mach and the numerical value represents the velocity of the bullet relative to the speed of sound at the time of the shot. Photos by Beat Kneubuehl.
“Going transonic” is generally not a good thing for bullets. The bullet can lose stability as it enters the transonic zone. It can also become less slippery, losing BC as a consequence of dynamic instability. In this video, Bryan Litz of Applied Ballistics analyzes what happens to bullet stability (and BC) as projectiles approach the speed of sound. Transonic effects come into play starting about Mach 1.2, as the bullet drops below 1340 fps.
Transonic Ballistics Effects Explained by Bryan Litz
What happens when the bullet slows to transonic speed, i.e. when the bullet slows to about 1340 feet per second? It is getting close to the speed of sound, close to the sound barrier. That is a bad place to fly for anything. In particular, for bullets that are spin-stabilized, what the sound barrier does to a bullet (as it flies near Mach 1) is that it has a de-stabilizing effect. The center of pressure moves forward, and the over-turning moment on the bullet gets greater. You must then ask: “Is your bullet going to have enough gyroscopic stability to overcome the increasing dynamic instability that’s experienced at transonic speed?”
Some bullets do this better than others. Typically bullets that are shorter and have shallow boat-tail angles will track better through the transonic range. On the contrary, bullets that are longer… can experience a greater range of pitching and yawing in the transonic range that will depress their ballistic coefficients at that speed to greater or lesser extents depending on the exact conditions of the day. That makes it very hard to predict your trajectory for bullets like that through that speed range.
When you look at transonic effects on stability, you’re looking at reasons to maybe have a super-fast twist rate to stabilize your bullets, because you’re actually getting better performance — you’re getting less drag and more BC from your bullets if they are spinning with a more rigid axis through the transonic flight range because they’ll be experiencing less pitching and yawing in their flight.
To determine how bullets perform in the “transonic zone”, Bryan did a lot of testing with multiple barrels and various twist rates, comparing how bullets act at supersonic AND transonic velocities. Bryan looked at the effect of twist rates on the bullets’ Ballistic Coefficient (BC). His tests revealed how BC degrades in the transonic zone due to pitching and yawing. Bryan also studied how precision (group size) and muzzle velocity were affected by twist rates. You may be surprised by the results (which showed that precision did not suffer much with faster barrel twist rates). The results of this extensive research are found in Bryan’s book Modern Advancements in Long Range Shooting.
Bryan notes: “A lot of gunpowder was burned to get these results and it’s all published in layman’s terms that are easy to understand”. If you’re interested in learning more about transonic bullet stability, you may want to pick up a copy of Bryan’s book.
Now they are discussing jacketed bullets and you stand there and say heck Sgt. Mike I shoot cast.
YEP OK they discuss the fact that it is hard to over-stabilize a “good” bullet so my question is can you cast as good a bullet as can be made by the jacketed crowd?
The answer is obvious we as casters need to pay attention to a multitude of factors in order to get on the level of jacketed bullet production of the 1950’s which wasn’t that good compared to today. While I am writing this I know some will set there and attempt to meely mouth excuses and say I’m picking on the bullet caster. not so there are several items brought out in the article above that we need to hold to:
1. ” The longer a bullet is for its diameter, the faster the twist has to be to stabilize it.”
Notice that weight is not used as a factor rather length.
2. “If you have a bullet with good concentricity in its jacket, over-spinning it will not [normally] hurt its accuracy potential.”
Well cast just doesn’t have a jacket but let’s look at that statement, if I have non fill out or inclusions within the bullet it’s just not going to be concentric. So how do we fix that?
Cast better bullets is the obvious answer, by paying attention to how and what we cast. We have to be able to measure things to determine how to consistently cast a “good” bullet.
Another method if the twist rate is high is to get an acceptable RPM rate by shooting faster or slower in order to get the rpm that that bullet’s construction will allow.
3. In the Transonic Article ‘Bryan also studied how precision (group size) and muzzle velocity were affected by twist rates. You may be surprised by the results (which showed that precision did not suffer much with faster barrel twist rates).”
“precision did not suffer much” that statement is with “good” jacket constructed bullets. Hmm since most here shoot cast, well this leaves one to the impression that too fast in fact can cause accuracy to suffer. As the simple fact that our projectile are not protected by a jacket that helps to maintain the concentricity and “good” bullet factor. Couple that with the fact that our bullets are shorter than a jacketed bullet we can easily shoot a slower twist accurately, the Miller Formula is called out in several of the articles, and I will quote the miller formula almost exclusively. We have to bear in mind this formula relies on a BOAT TAIL not a flat base (look here http://www.bergerbullets.com/ballistics/flat-based-bullet-recommended-twist-rates/ ). Can we cast a bullet that will meet what we need? Sure we can, we cast better and pick the appropriate twist rate for the length of our projectile. We pay attention to the minute details when we are seeking optimum high level of performance. Or we simply lower the velocity to the level that offers the accuracy with the twist rate that the factory gives us, and hapless casting methods. Both methods are complete acceptable to each of us.
Some of the factors not discussed is how the lands and grooves configuration plays into the twist rate. As several barrel manufacturer whom will cut a custom land and groove will tell you that it will alter the twist rate rules. This last statement will only effect the gent that goes and specifies a non standard used land and groove dimension, I’m not referring to number of grooves or the bore vs groove diameter.
While I know my posting will open more questions much like a can of worms, I leave you to your research, and reading.
- August 10, 2016 at 8:40 pm #29372AnonymousInactive
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Great topic. I am reading and learning. Who says “you can’t teach on old dog new tricks”. Thanks Guys.
- August 11, 2016 at 4:11 pm #29381Larry GibsonParticipant
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Now Mike, we all know all this mumbo jumbo about stability, RPM and bullet quality just isn’t so…….
Obviously these ballisticians received a formal scientific education but have not yet studied and learned anything post grad over at the CBF forum of higher learning. The experts there could certainly educate these ill informed ballisticians on the true meaning of ballistics, especially cast bullet ballistics.
And to misquote Bryan Litz like that……obviously they don’t know only starmetal a 45 2.1 can properly interpret what Litz says…….
We have thus learned from the cast bullet garu’s, experts and self made geniuses that higher RPM means nothing and has no adverse affect on cast bullets at higher velocities, slower twists provide no accuracy advantage and who needs to cast quality bullets with soft alloys……..just ask them……
- August 11, 2016 at 5:15 pm #29382
No burrs under that saddle . 🙂
I’m too invested with the whole twist gig to deny it’s function. It is exactly why I have 3 30 cal twists that won’t talk to each other. ….although in 2cases the results make no sense and contridict everything learned in the other 5…
It only matters when it does as long as you are inside the guidelines and everything is as good as you can get it. …. the above examples are at least consistent in which rules that want to follow and which 1s they just don’t care about.
Just to be clear twist matters to every projectile. Aerodynamics alter the equation .
Some combinations well inside the rules just won’t work except in a vacuum.
Now that I have that beat through the thick skull things are working better.
- August 11, 2016 at 5:52 pm #29384
Now Larry, Following your method, I’d say we nailed the lid down on that coffin so tight only a complete imbecile would dispute it. Being that imbeciles don’t like word to get around about their condition, and disputing sound reason does exactly that, they take the only course of action left available to them: Silence those speaking the truth. So they did.
What I take great personal enjoyment from is that we slammed the door so hard on their tom-foolry, none of them will discuss HV on any of the various cast bullet forums.
It is a banned subject.
Why? Because we are the only ones who did it for real, did it over a chronogragh, did it at extended ranges, did it over and over and over and explained it so that others could do it just as easily, and those people also attest to the validity of our experiments.
It was done every time utilizing your knowledge, my rifles, Bjornb’s indomitable testing regiments, along with occasional place holder targets by myself and Sarge.
In fact, I just shipped another XCB rifle a few months ago. The owner had this to say, and I quote:
“There’s guys that cant do this with jacketed bullets! This is freaking awesome!!!!! Thanks. You have made it real easy. Haven’t done anything different on this one, that I haven’t done on others, and they don’t shoot.”
It’s all good to claim to be able to do something that is unattainable until somebody shows up who can do it for real, often, and get others doing it too.
Yeah, we got kicked off the forum. Can you blame them? They lied, cheated, took credit for something they only did once on a good day with the wind at their back, and in the course of satisfying our curiosity and showing people how to do this for real, we trampled all over their well built house of cards. Just plain demolished their own belief in their “Abilities” because when asked, they couldn’t produce anything even close to what you and Bjorn are cranking out on a daily basis.
Seems childish, and it is, but there ya go.
Honestly, who but a complete adolescent would shoot 2000 shots till he got a magical cluster that looked halfway decent then post right along side folks doing what we have been, that “he’s done it too, and better”, and then get mad when we say “Cool! Lets see what it does at 200 yards”???
Seriously, I don’t know about you, but any forum that sees imbeciles like that as a major asset and protects their delicate little feelings by banning the only people who have ever demonstrated HV to the level of proficiency that we have are about half a bubble off the plumb.
Most cast bullet forums would see four guys making huge strides in one of the most hotly debated subject of all time as a serious asset. Here at GSF, we do!
In fact, if somebody comes here claiming to shoot faster than we do, I dare say I speak for all of us when I say if when asked for more details on validity of testing, and the guy doesn’t blow smoke, he would be welcomed warmly.
Unfortunately, I know of only a select few people who can demonstrate accuracy and speed claims on demand, and that’s you, Bjorn, Sgt.Mike, myself, and the people who have bought my rifles and applied your method to them, and one other who PMed me and described in detail that he did something very similar, but when asked how, he described a nearly identical method to what we use, developed completely on his own.
Trying to shoot standard cast bullets at HV while blatantly ignoring the basic ballistic needs of those projectiles, is akin to rollerskating uphill in the rain.
- August 11, 2016 at 8:23 pm #29386
Goodsteel;n8737 wrote: ………….. They lied, cheated, took credit for something they only did once on a good day with the wind at their back, and in the course of satisfying our curiosity and showing people how to do this for real, we trampled all over their well built house of cards…………………………
I heard they was hired by the Clinton foundation and some others by the DNC for the Hillary camplain
- August 11, 2016 at 8:56 pm #29388
One other advantage that most have not discussed or when they do get blown off is spin drift.
One of the results is it assist in precession on a projectile. I not against the High RPM thoughts that most yell about but the author at Accurate shooter quoted this:
“Once I loaded some 35gr HP bullets in a 22-250 Ackley with a 1:8â€³ twist. After putting three shots down range, the average velocity was 4584 FPS with an RPM level of 412,560. The group measured .750â€³ at 100 yards.”
Cool but how much spin drift did you have on that 600 to 800 yard Prairie Dog with the 1-8″ twist when the wind was dead still ?
(BTW in the calculator I zeroed out wind effect this will show the Spin Drift on the bullet based on twist)
22-250 53gr Sierria 1-8″ twist @4500 fps Range Drop Windage Velocity Energy Time (yd) (in) (in) (ft/s) (ft•lbs) (s) 0 -1.5 0 4521.2 2405.2 0 100 0 0.1 3925.1 1812.8 0.071 200 -0.8 0.2 3402.3 1362.1 0.153 300 -4.6 0.5 2938.6 1016.1 0.248 400 -12.4 1 2511.7 742.3 0.359 500 -25.8 1.7 2119.2 528.4 0.489 600 -47.1 2.8 1763.4 365.9 0.644 700 -79.7 4.5 1445.3 245.8 0.832 800 -129.2 7.1 1197.2 168.7 1.061 900 -202.9 10.7 1038.5 126.9 1.332 1000 -308.7 15.6 941.3 104.2 1.636
But what if I shot a 1-12″ twist?
22-250 53gr Sierria 1-12″ Twist Range Drop Windage Velocity Energy Time (yd) (in) (in) (ft/s) (ft•lbs) (s) 0 -1.5 0 4521.2 2405.2 0 100 0 0 3925.1 1812.8 0.071 200 -0.8 0.1 3402.3 1362.1 0.153 300 -4.6 0.3 2938.6 1016.1 0.248 400 -12.4 0.6 2511.7 742.3 0.359 500 -25.8 1 2119.2 528.4 0.489 600 -47.1 1.6 1763.4 365.9 0.644 700 -79.7 2.6 1445.3 245.8 0.832 800 -129.2 4.1 1197.2 168.7 1.061 900 -202.9 6.2 1038.5 126.9 1.332 1000 -308.7 9 941.3 104.2 1.636I
But what if I shot a 1-14″ twist which is really supposed to be the cat’s meow for that bullet?
22-250 53gr Sierria 1-14″ Range Drop Windage Velocity Energy Time (yd) (in) (in) (ft/s) (ft•lbs) (s) 0 -1.5 0 4521.2 2405.2 0 100 0 0 3925.1 1812.8 0.071 200 -0.8 0.1 3402.3 1362.1 0.153 300 -4.6 0.2 2938.6 1016.1 0.248 400 -12.4 0.5 2511.7 742.3 0.359 500 -25.8 0.8 2119.2 528.4 0.489 600 -47.1 1.4 1763.4 365.9 0.644 700 -79.7 2.2 1445.3 245.8 0.832 800 -129.2 3.4 1197.2 168.7 1.061 900 -202.9 5.2 1038.5 126.9 1.332 1000 -308.7 7.6 941.3 104.2 1.636
- August 11, 2016 at 9:14 pm #29389
Kind of explains why a certain Savage 06’walks right as velocity increases b but it’s sisters and cousin dont.
I wonder if you would run 30 caliber 150 at 2700 fps for a 12,10 and 8.5 twist. ? My pocket calculator doesn’t include spin drift in as much as having a field for twist.
- August 12, 2016 at 12:19 am #29391
.308 150gr sierria gameking @2700fps
Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (in) (MOA) (in) (MOA) (ft/s) (none) (ft•lbs) (s) (in) (MOA)
0 -1.5 *** 0.0 *** 2707.8 2.428 2441.7 0.000 0.0 *** 100 -0.0 -0.0 0.1 0.1 2479.0 2.223 2046.5 0.116 0.0 0.0 200 -4.2 -2.0 0.5 0.2 2261.5 2.028 1703.2 0.243 0.0 0.0 300 -15.2 -4.8 1.1 0.4 2055.0 1.843 1406.3 0.382 0.0 0.0 400 -34.4 -8.2 2.1 0.5 1860.0 1.668 1152.1 0.535 0.0 0.0 500 -63.8 -12.2 3.4 0.7 1663.8 1.492 921.8 0.705 0.0 0.0 600 -105.7 -16.8 5.3 0.8 1479.3 1.326 728.7 0.897 0.0 0.0 700 -163.7 -22.3 7.9 1.1 1318.0 1.182 578.5 1.112 0.0 0.0 800 -241.6 -28.8 11.3 1.3 1185.1 1.063 467.7 1.352 0.0 0.0 900 -344.4 -36.5 15.7 1.7 1084.7 0.973 391.8 1.618 0.0 0.0 1000 -476.7 -45.5 21.1 2.0 1011.9 0.907 341.0 1.905 0.0 0.0
- August 12, 2016 at 12:23 am #29392
Sierria .308 150gr Game king @ 2700ft/s
Range Drop Spin Drift Spin Drift Velocity Energy Time (yd) (in) (in) (MOA) (ft/s) (ft•lbs) (s) 0 -1.5 0 *** 2707.8 2441.7 0 100 0 0.1 0.1 2479 2046.5 0.116 200 -4.2 0.5 0.2 2261.5 1703.2 0.243 300 -15.2 1.1 0.4 2055 1406.3 0.382 400 -34.4 2.1 0.5 1860 1152.1 0.535 500 -63.8 3.4 0.7 1663.8 921.8 0.705 600 -105.7 5.3 0.8 1479.3 728.7 0.897 700 -163.7 7.9 1.1 1318 578.5 1.112 800 -241.6 11.3 1.3 1185.1 467.7 1.352 900 -344.4 15.7 1.7 1084.7 391.8 1.618 1000 -476.7 21.1 2 1011.9 341 1.905
- August 12, 2016 at 12:26 am #29393
Sierria .308 150gr Game king @ 2700ft/s
Range Drop Spin Drift Velocity Energy Time (yd) (in) (in) (ft/s) (ft•lbs) (s) 0 -1.5 0 2707.8 2441.7 0 100 0 0.1 2479 2046.5 0.116 200 -4.2 0.4 2261.5 1703.2 0.243 300 -15.2 0.9 2055 1406.3 0.382 400 -34.4 1.6 1860 1152.1 0.535 500 -63.8 2.7 1663.8 921.8 0.705 600 -105.7 4.2 1479.3 728.7 0.897 700 -163.7 6.2 1318 578.5 1.112 800 -241.6 8.9 1185.1 467.7 1.352 900 -344.4 12.3 1084.7 391.8 1.618 1000 -476.7 16.6 1011.9 341 1.905
- August 12, 2016 at 12:28 am #29394
Sierria .308 150gr Game king @ 2700ft/s
Range Drop Spin Drift Velocity Energy Time (yd) (in) (in) (ft/s) (ft•lbs) (s) 0 -1.5 0 2707.8 2441.7 0 100 0 0.1 2479 2046.5 0.116 200 -4.2 0.3 2261.5 1703.2 0.243 300 -15.2 0.7 2055 1406.3 0.382 400 -34.4 1.3 1860 1152.1 0.535 500 -63.8 2.1 1663.8 921.8 0.705 600 -105.7 3.3 1479.3 728.7 0.897 700 -163.7 4.9 1318 578.5 1.112 800 -241.6 7 1185.1 467.7 1.352 900 -344.4 9.7 1084.7 391.8 1.618 1000 -476.7 13 1011.9 341 1.905
- August 12, 2016 at 12:37 am #29395
Sierria .308 150gr Game king @ 2700ft/s
Range Drop Spin Drift Velocity Energy Time (yd) (in) (in) (ft/s) (ft•lbs) (s) 0 -1.5 0 2707.8 2441.7 0 100 0 0.1 2479 2046.5 0.116 200 -4.2 0.3 2261.5 1703.2 0.243 300 -15.2 0.6 2055 1406.3 0.382 400 -34.4 1.1 1860 1152.1 0.535 500 -63.8 1.8 1663.8 921.8 0.705 600 -105.7 2.7 1479.3 728.7 0.897 700 -163.7 4.1 1318 578.5 1.112 800 -241.6 5.8 1185.1 467.7 1.352 900 -344.4 8.1 1084.7 391.8 1.618 1000 -476.7 10.9 1011.9 341 1.905
Why did I include the 1-14″ twist because the 150grain Gameking is still stable
Stability Input Data Caliber: 0.308 in Bullet Weight: 150.0 gr Bullet Length: 1.110 in Plastic Tip Length: 0.000 in Muzzle Velocity: 2700.0 ft/s Barrel Twist: 14.0 in Temperature: 59.0 °F Pressure: 30.84 in Hg Output Data Stability: 1.417
Stability The Miller stability value. It should be between 1.3 and 2.0 to ensure stabilty
Now keep in mind that the WIND has been ZEROED OUT this is just the drift of the rotation of the bullet.
With a wind from left to right with a right hand twist it is increased in value. In order to beat wind a HIGH BC and ability to retain velocity at the desired distance (time of flight) the longer the bullet takes to get there the more the elements have time to effect the path.
This explains why the heavy 6mm/ 6.5mm will buck wind so much better with a slower start velocity than some 30 calibers, but new bullets are being introduced that will soon catch up..
Using the 7.62mm M80 fired from a 1-10″ twist at 2750 fps we can see the rotational decay
Does it impact accuracy or stability yes / no but what we see is the bullet retains quite a bit of it’s rotation throughout it’s path to target.
Again faster is better as the rotational decay is even less. Like Drop, and windage movement it is a timed event. (107,229rpm)
Range Muzzle 100 200 300 400 500 1000 Percent of spin remaining 100 98 96 93 91 89 75 Bullet RPM 198,000 194,000 190,000 184,000 180,000 176,000 148,500
- August 12, 2016 at 1:47 am #29398
Wow at long range the 3.5 inches of twist makes a lot of difference 7 inch from the 12 twist and10″ more than the 14 twist .
- August 12, 2016 at 1:55 am #29400
When I was crunching numbers to calculate what twist rate I wanted for the 30-06 build that I did
I chose the 1-13.5″ Twist in the 30-06 because?
Range Drop Windage Velocity Energy Time Rotational Decay RPM (107,229rpm min for a 1.3 SG) (yd) (in) (in) (ft/s) (ft•lbs) (s) 0 -1.5 0 2707.8 2441.7 0 100.00% 144,416 100 0 0.1 2479 2046.5 0.116 98.00% 141,528 200 -4.2 0.3 2261.5 1703.2 0.243 96.00% 138,639 300 -15.2 0.6 2055 1406.3 0.382 93.00% 134,307 400 -34.4 1.1 1860 1152.1 0.535 91.00% 131,419 500 -63.8 1.8 1663.8 921.8 0.705 89.00% 128,530 600 -105.7 2.9 1479.3 728.7 0.897 700 -163.7 4.2 1318 578.5 1.112 800 -241.6 6 1185.1 467.7 1.352 900 -344.4 8.4 1084.7 391.8 1.618 1000 -476.7 11.3 1011.9 341 1.905 75.00% 108,312
As we can clearly see the 150 gr Sierria GameKing will be stable throughout it’s flight
- August 12, 2016 at 2:11 am #29401
When I was crunching numbers to calculate what twist rate I wanted for the 30-06 build that I did
I chose the 1-13.5″ Twist in the 30-06 because?
for this one i’m using the 155gr Sierria Palma at a 2900ft/s
With a 30″ barrel the 2900fps will be easy to obtain Now I’m a little fast in the RPM, and just a little bit over supersonic.
But if the temp drops to say 30 degrees F, I’ll need the extra RPM to stabilize at the Long Line (1000 yds)
Range Drop Spin Drift Velocity Time Rotational Decay RPM
for a 1.3 SG)
(yd) (in) (in) 1-13.5″ Twist (ft/s) (s) 1-13.5″ 1-14″ 0 -1.5 0 2907.4 0 100.00% 155,061 149,523 100 0 0.1 2689.2 0.107 98.00% 151,960 146,533 200 -3.3 0.2 2479.9 0.223 96.00% 148,859 143,542 300 -12.3 0.5 2279.9 0.35 93.00% 144,207 133,495 400 -28 0.9 2089.7 0.487 91.00% 141,106 136,066 500 -51.7 1.5 1908.9 0.637 89.00% 138,005 133,076 600 -84.9 2.3 1735.9 0.802 700 -129.7 3.4 1570 0.984 800 -188.7 4.8 1411.5 1.185 900 -265.2 6.5 1261.3 1.41 1000 -363.7 8.8 1123.2 1.663 75.00% 116,296 112,143
- August 12, 2016 at 3:22 am #29404
Looking at the 175gr Sierra with the 1-13.5″ I should be about 116,267 rpm at 90 degrees here in Arkansas which is a moderate day.
Now usually on a hotter day the velocity goes up and the needed RPM goes down hence on a 100 degree day I should be able to shoot these
with ease. If
IF I expected to shoot in a cooler climate I would need to spin a half to a inch shorter, if my choice was this bullet I would twist 1-12 to 1-12.5″
This increase in rpm would give me a little bit more spin drift but it’s all a pay off I would be able to maintain stability without much sacrifice.
But here is the 175gr with the 1-13.5″ Twist but I should be able to easily exceed the MV shown here by another 200 or so ft/s.
Range Drop Spin Drift Velocity Energy Time Rotational RPM (yd) (in) (in) (ft/s) (ft•lbs) (s) Decay 1-13.5″ Twist 0 -1.5 0 2786.4 3016.4 0 100.00% 148,608 100 0 0.1 2599 2624.4 0.111 98.00% 145,636 200 -3.7 0.2 2419.3 2274 0.231 96.00% 142,664 300 -13.3 0.5 2246.8 1961.2 0.36 93.00% 138,205 400 -29.8 0.9 2081.2 1682.8 0.499 91.00% 135,233 500 -54.3 1.4 1922.9 1436.6 0.649 89.00% 132,261 600 -88.3 2.2 1771.9 1219.8 0.811 0 0 700 -133.3 3.1 1627.2 1028.7 0.988 0 0 800 -191.6 4.3 1493 866 1.18 0 0 900 -265.4 5.8 1371 730.3 1.39 0 0 1000 -357.8 7.7 1263.2 619.9 1.618 75.00% 111,456
- August 12, 2016 at 3:28 am #29405
Like Harter pointed out this (spin drift) really does not matter until you go to the long line.
Now will it actually outperform a faster twist, the only way to find out is to sling up and fire the course.
- August 12, 2016 at 5:20 pm #29410
Have you ever watched a bullet trace through a spotting scope go left then right then back left then impact?
Or had your Zero on target then all of a sudden your shot group go right and high for no apparent reason?
Or even the opposite a good zero then the strike is low left.
You have just observed the Magnus effect. HUH you say?
The Magnus effect is the commonly observed effect in which a spinning bullet curves away from its principal flight path. This phenomenon comes from Newton’s third law that the deflective force on the body is no more or less than a reaction to the deflection that the body imposes on the air-flow.
Usually this is insignificant compared to other factors such as drag. Normally drag is a function of the form factor (shape) of the bullet.
But it does affect the bullets stability, which in turn can create more drag as well as other factors which will slow the bullet down. This will cause the bullet to drop more than if the effect was not introduced.
But let’s look at this a bit the Magnus effect acts on the bullet’s center of pressure instead of its center of gravity. This means that it affects the yaw angle of the bullet: it tends to twist the bullet along its flight path, either towards the axis of flight (decreasing the yaw thus stabilizing the bullet) or away from the axis of flight (increasing the yaw thus destabilizing the bullet). The critical factor is the location of the center of pressure, which depends on the air flow field structure around the spinning bullet, this depends mainly on the bullet’s speed, also the shape, air density and surface. Destabilizing effect occurs when the center of pressure is ahead of the center of gravity. A stabilizing effect occurs when the center of pressure is behind the center of gravity.
A picture is worth a thousand words so I have snatched these graphics via the internet to illustrate:
As we can see here the wind is from the right to left with a right hand twist.
The faster the wind blows the more the effect (which is downward), also the faster the bullet is spinning the more the effect.
This is still a right hand twist with the wind left to right. (which is upward and will actually be right and up)
Again same principle either fast spinning or a faster wind will increase the effect.
Air Temperature will also play in here as the density of the air is different. Humidity and other factors.
The slower I spin this projectile in X amount of wind the less the effect versus a faster spinning but I must spin it fast enough to be stable before it gets into the wind. Also the Form factor will play in here as well but that is another discussion.
Is this a area that needs great attention????? .. well no it doesn’t matter till it matters , but with the knowledge of what is happening, the shooter can develop his “dope”
in other words while the tables gives a X value they are a guide in longer range shooting.
The shooter plugs in the values from the ballistic tables, then realizes that he may need to add more or even less correction because of a multiple reasons that occurs. If he is observant he’ll mental note the wind, the Temp how much mirage, as well as the weather condition including sunlight as it all make a difference in small amount that adds up to a bigger degree it is what is referred to as tolerance stack up in the machining world.
This occurs even if the wind is not blowing at your location. It is blowing somewhere along the bullets path. Here is when reading the wind and having good “dope” values experience at X range with X amount of wind will separate the men from the boys on that shot.
In other words to dummy all this all down.
Magnus effect is the combination of spin drift with the effect of wind at longer ranges.
The only way to develop good “dope” is to pull the tables, shoot it then correct to hit point of aim, this must be done multiple times to validate the conditions and distance for that shot.
This is why the old timers always said overspin is a sin.
- August 12, 2016 at 8:15 pm #29414
I have experienced the “perfect storm” of that effect with a 350 yd shot that passed through a wind shear with a 10 twist in a 25-06′ ….Man that was a long long time ago . It sticks with me because the rifle was set up up for zero at 200yd and in real world shooting was only about 16″ low at 400 and 24 at 500. We had a flat that allowed out to 740 yd . Anyway the shot was across a saddle on a ridge top . We had a 10-12,000 lb granite boulder for a rest and a 10 mph left to right and about 50 ft down hill . I held the wind and correct hold over for a nice clean boiler house …….. the hit came at point of hold 2″ under the back line and just out of the ribs through the neck bones. Which says to me that whatevereffects were in play created a situation all of the normal bench no wind correctionswere were negated including nominal drop..
The rifle amounts to an M40 in walnut and 25-06 .
- August 13, 2016 at 12:24 pm #29424
Fascinating addition to the topic Sarge. I’ve never read about the Magnus effect before (or if I did it was in one ear and out the other.) but like Harter says, it may explain the occasional shot that does something unexpected.
- August 13, 2016 at 5:09 pm #29428
Well gents to be honest we haven’t scratched the surface yet.
There is way more that plays into a bullet’s stability. B.C, coefficient of drag (C.D.) are just two more items that comes to my mind. Both of those are married to the hip for a bullet.
Before Felix passed he made a statement on Cast Boolit Forum that went waaayyyy over the top of peoples head, and no one paid attention to it. Something to the effect that a precision shooter had to be a weather man. Why did he make that statement, Temperature, humidity, dewpoint, wind, all plays in and effects stability. While we use the greenhill and / or the miller formula to predict how something will fly, sometimes it just doesn’t work like predicted although that is seldom. Sometimes it’s because of weather shoot it again on a different day and compare the results.
Larry Gibson shown us something that noone picked up on, during his testing to get to high velocity with cast. Go back and read the printouts of his Olher pay attention to the BC he reported. He did testing that showed the cast bullet BC degrading at a very high degree from muzzle to midrange yardage. Why does the cast bullet bullet do that when jacketed bucks it so much better?
Flat base pay attention to the low pressure area, this will slow the bullet down
good pictorial of spin drift
notice the secondary shock wave from the cannalure so how many lube grooves do you have??
Also note the low pressure area it is less than a flat base
don’t think I need to explain this one
just another example of a bullet producing spin drift which if done consistently it is something that is just not noticed by the shooter
unless he is shooting bench rest or precision like F class at the long line and beyond
Most ballistic software will calculate the spin drift with the wind drift if it has the ability to input the twist rate.
Finally I’ll leave you with a thought surface friction / cohesion cast versus jacketed.
- August 13, 2016 at 5:44 pm #29430
This is very very bad……. …… my satisfactory 3 MOA rifles that I’ve unintentionally worked down to 1.2 MOA rifles have been worked through all of this . By comparison to the finesse of Tim’s sub 5 decimal machine work and 4 places of bullet sizing I’m a hack with a 36″ pipe wrench and a sledge hammer. I can admit that and be ok with it. .I wonder with the question and applied learning here should this be a sticky ?
- August 13, 2016 at 6:09 pm #29431
OHHHHH Harter, I’m not done LMAO
We have not discussed the gyroscopic center of gravity in relationship to mechanical center of gravity within the bullet (which is the heart of the RPMth whether you subscribe or not) , ballistic coefficient, coefficient of drag. Much less discussed the relationship of the barrel blank quality which affect the harmonics as much if not more than the cutting of lands and grooves, which profile to assist in keeping the harmonics uniform resulting in gyroscopic center of gravity in alignment with the bullets true center of gravity. Although I wish Larry would jump in here a bit and hit the BC that he observed with the 30XCB and other bullets.
Alone all of these factors are extremely small and some factors correct others, at times they sometime compound the effect.
This all effects what we call accuracy.
In closing my response to your post working a 3 MOA rifle down to a 1.2 MOA is no small feat Sir . Yes IF I was you I would be extremely proud of that fact.
I’m just trying to share what I know so if I seem condescending I assure you I’m not. I’m just sharing what I’ve been taught (some self some formal) /seen over the years. Instead of walking away, I advise to stand back and observe the forest, not just the tree. The tree is just one aspect of the forest but an important one
- August 13, 2016 at 7:40 pm #29435
Nope this is probably the most tame polite discussion I’ve seen on the matter . .
I think save for the guy that fired his 1st shot last week would be aware of the most remedial points of basic knowledge, the ball is bestfor shot range and swooppy pointy bulletsare for far away. I’ve said this many times ,we are pushing cast bullets to places that they have never gone . It is because of having places like this that allow us to build a knowledge base in weeks that couldn’t be done in months a few years ago . We can take an experiment with known success (whether or not we can explain why it worked)and build on that . We can also wander off out in the weeds and take the stuff that we know works and push the limits being able to come back and share that success or spectacular failure for the next guy to build on or look at and fix . . It takes hours or days to a year to go from buying a 1st pistol or rifle to being able to cast and load 2 MOA ammo and you don’t have to wait 5 yr for the next book to see if it or the last 25 you read while you were waiting will answer the question about the load that is just perfect to some point then falls apart whether it is a result of shape, hum or something that happened between the sear and the muzzle . Sometimes it’s simple like the 45 Colts carbine 25,50,75 yd groups at 100 it looks like 00B out of a punt gun . It’s an aerodynamic flaw that is a huge problem from 1050-1150 fps . Slower and heavier or faster and slicker …… or don’t shoot past 75 yd. Sometimes it’s a proven sub MOA 30-06′ that just won’t shoot that bullet at that speed over that powder with that primer and it shows up with 10 under a quarter @100 and 10 in a tea cup @ 200 and at 250 the superformance 165s are barely on a 48×48 together …….. yep I could have heard that cussing 2 states over .
Back on track . Having an airplane background I’ve done things and followed paths that were always there and probably once or twice inspired a thought process to figure why it worked and in some cases why it doesn’t when it should .
I have a 308 without any regard for shape ,will shoot up to 175 gr (the 301618,172 gr, works but the Hornady 180 RN tumbles) break that limit forget it. Meanwhile it’s older cousin in a random I wonder if experiment shoots the NOE 312-230 ,in a couple of work ups with no intention of presuing the loads , into nice round holes . Ok so they were 8″ apart but it was in a 30 WCF with the 12″ twist. It should not work at all . The shape now plays a huge roll and makes me want to stuff a few 230 s in the 308 that won’t shoot a jacketed 180 shorter than the 168 s that shoot fine .
I’ve lost track of where I was going…… umm …… it all matters just more in some cases than others ?
- August 18, 2016 at 2:33 am #29544
Here is a video of a 22:R in flight. watch the shock wave and the secondary wave
Just thought ya’ll would be interested
- August 18, 2016 at 2:38 am #29545
This is a 22LR in flight thought ya’ll would like the shock wave and secondary wave
[video src="https://upload.wikimedia.org/wikipedia/commons/transcoded/c/c3/Bullet_Wiki.ogv/Bullet_Wiki.ogv.360p.webm" /]
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