- February 25, 2017 at 3:49 pm #33663
A while back I brokered a deal on several Brux barrels all in 30 caliber ranging in twist from 11.5 to 1-14″, Lengths also varied. Tim fitted these barrels, Lars45 has one. I twisted mine in 1-13.5″ for a finished length of 30″ caliber 30-06 bore dimensions 298X308 , but Tim and I did some things that setup a high degree of success on mine that was not done on the others. While I’ll talk about my break in regiment which will not guarantee success but doesn’t hurt. Tim introduced the barrel block Idea on a stock that I ordered, The block is approx 3″ in length which in hindsight it could have been doubled in length for even greater success than I currently enjoy, but I have no regrets on what was done or how it was done. I only make the remark for Tim’s information that it Should work to even a greater degree
Tim remarked a while back that mine was so far the most accurate, but why? Well it really is a easy answer barrel stiffness, or rigidity ( this article will describe it http://riflebarrels.com/a-look-at-the-rigidity-of-benchrest-barrels/) thus the block anchors the barrel and fools it to thinking ( actually forces it to perform like shorter barrel) Thus my 1-13.5″ twist that is 30″ long actually is 26.25″ free length because the other 3.75″ is supported in the block and action. Because the action is floated and the barrel block is utilized the vibrations that the factory firing pin in pretty well damped by the block, another plus is the big aluminum clamping block also acts as a heat sink . Now IF we (Tim or I) had doubled the length to 6″ on the block the barrel would have acted like a 23.25″ which would have greatly increased the rigidity. Another thing that was done was the contouring which I really do not want to get into because right now Tim nor I can provide any real proof that it helped or was just a cool factor left over from Dr. Mann.
But I did procure another barrel that Bjorn offered to me ( many thanks to Bjorn) that will be used for a test to test the contour theory at a way later date that blank is setup up for a 31″ finished length with a 1-14″ twist same bore as Mo’ Chuslia. Which I will probably ask Tim chamber in the same caliber as Bjornb’s “Bertha” only because I had a blast with Bertha when Bjorn had her at Tim’s.
While some may scoff at this, Bjorn did something with a factory Winchester 70 in 30-06 that was amazing he cut the barrel back to 16″. As this was Bjorn’s project I don’t want to dive too deep into except to say because the barrel was cut back it radically increased the stiffness or rigidity to his factory barrel. And the target showed the results very vividly. I’m in hopes Bjorn will post his observations in this thread.
- February 26, 2017 at 1:09 am #33667bjornbModerator
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I tried to write a new thread about my recent trip to Arkansas, but I couldn’t get the pictures from the trip to upload, so I’ll wait for the new forum software to be operative. Had a great time with Sarge and Tim, shooting several new rifles that Tim had built for me over the last 6 months or so. The new Broughton barrel (1:12 twist) that Tim chambered in 30BR and fitted to Bertha (the rifle with the dragonfly) shot amazingly well.
Stay tuned for a full road trip report.
- February 26, 2017 at 1:31 pm #33671kensParticipant
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Are you building a bench rail gun, or, a shoulder fired rifle?
- February 26, 2017 at 2:40 pm #33675GoodsteelKeymaster
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Its a dedicated bench gun. And its already finished.
- February 26, 2017 at 3:18 pm #33676
Ken it is a bench gun that is capable of being shoulder fired. As I like shooting truck axles for barrels.
Currently the Remington 721 that I call Mo Chuslia is 23 pounds with a 3″ barrel block in a Richards (Target Culbertson) with a 30″ Brux 1-13.5″ twist bore 298×308 caliber 30-06.
The barrel block allows the barrel and the action to float. This allows me to set the same action up for another caliber which after firing Bjorns build (Bertha) in 30 Benchrest I was impressed. After that is when Bjorn offered me the blank same bore as mine 1-14″ Twist finished length 31″ so I took him up on it.
My intent is to setup Bjorn’s old barrel in 30 Benchrest which will allow me to change barrels and calibers. Because I’ll wind up whittling that 31″ down to say a 24″ inch is sorta disturbing to me in one sense, the other not so much as I can just have it long. The rifle will lose a bit of weight in putting in a shorter barrel which I figure it will tip the scale at 20 vs 23 pounds.
going back to the 30-06 barrel that is currently in the 721 the picture that Tim Posted is what is on her right now . As I stated earlier Tim nor I can say this profile helps this rifle or not. ( but, Tim and I have a idea to see if it does with the other Brux barrel)
As I have plans on swaging 30 caliber bullets this rifle was built as a test bed for that purpose. 155gr palma shoot outstanding in this barrel, The XCB Bullet is a shoe in as well.
I have two other actions that need rebarreling that I could use in lieu of the 721 ( a 700 in 7mm Mag, a 722 in 6mm Rem) even though right now I’m thinking I want the 721 to have two barrels setup for it one in 30-06 the other 30 BR. But, I may just change my mind and use the 700, I just really don’t want to spend the extra money on a standard face bolt right now. Even though I could just use the same stock.
- February 26, 2017 at 3:35 pm #33677
Above is the current barrel deflection based on profile (sans Dr Mann) per computer modeling
below is a computer modeling if the barrel was just left at 1.250″ straight bull
As you can see per computer modeling show almost identical results. The above model was integrating the barrel block system that Tim really almost begged me to do which I agreed.
added after posting
wow the first graphic disappeared OK any way both graphics was basically the same within less than 0.1 millisecond.
What is interesting to note is I have two perfect bullet exit times .09ish and 1.4ish milliseconds.
Added later Ok the upgrade is not working for graphics
- February 26, 2017 at 4:02 pm #33678
Here is what is projected for the same setup calculating a standard sporter profile
Normally a bullet leaves the bore sometime between 1 and 1.6 milliseconds as a rule but the caliber will shift it a bit as well as powder choices.
But sticking to 1 and 1.6 milliseconds we can see why many have issues finding that sweet spot . This barrel should do well with 0.8, 1.2, 1.9 exit times
These exit times can be calculated with Quick Load
As a side note I calculated all the above as a 30″ bore size .308 barrel in a 3″ barrel block supported 1.11″ inside the action that gives a 25.89″ free length
- February 26, 2017 at 5:53 pm #33680JPHollaParticipant
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Another thing the barrel block does is takes the weight and inherent sideways stress off the action. I’ve been meaning to build one for a while but haven’t gotten around to it yet.
- February 26, 2017 at 6:54 pm #33681
Earlier I attempted to up load graphics showing the barrel harmonics differences.
here is the barrel unclamped:
now for the clamped which will react as a 25.89 or roughly a 26 inch barrel unclamped
Each barrel configuration has about 6 to 7 nodes that could produce great accuracy what varies greatly is the exit time of the bullet from the barrel this is where Quickload plays in.
As small as a 375 fps variance can lead to a millisecond difference in exit time. To the average hunter none of this of any interest, but to someone playing with bench guns well it’s a start to load development and powder selection
- February 26, 2017 at 7:00 pm #33682
Barrel harmonics graphics removed….
- February 26, 2017 at 7:26 pm #33683
JP, yeah I hear you on your build, I would advise doing so, it is worth the effort. We both know a ‘Smith that could pull off a good build that would be highly regarded.
yes I know shameless plug there but sometimes the truth is just that.
- February 26, 2017 at 8:10 pm #33684
You run a DFT on those curves to see the fundamental and harmonics? I assume a QL model, not actual data – realize target shows effect. Where is crown exit on the graph? I get 330 hz for fund. & 990 for 3rd. harmonic. About the same from pressure curves for L.G. For free floated, whip should not be just in verticle.
- February 26, 2017 at 10:22 pm #33687
popper;n14479 wrote: You run a DFT on those curves to see the fundamental and harmonics? I assume a QL model, not actual data – realize target shows effect. Where is crown exit on the graph? I get 330 hz for fund. & 990 for 3rd. harmonic. About the same from pressure curves for L.G. For free floated, whip should not be just in verticle.
Not Quickload I used Border Barrel software which is predictive in nature based on contour (also assumes 50,000 psi). Just easier than calculation in long hand exactly what Dan Lija alludes to in the earlier post. I don’t own Quickload I have to bug friends for data from it so I cant provide the time in milliseconds the bullet will cross the crown.
- February 27, 2017 at 2:48 am #33707
My curiosity is how the barrel response & pressure curve combine.
- February 27, 2017 at 2:04 pm #33724
popper;n14509 wrote: My curiosity is how the barrel response & pressure curve combine.
I think there are a lot of people with the same curiosity Popper.
In the model that Border uses it is based on the 308 by default for a pressure curve and operating pressure 50,000 psi as the only inputs are barrel contour, weight of the firearm, distance to CG from bore center line, bore dia, . My reason for posting the graphics was to show how using the barrel clamp forces the barrel to respond like a shorter barrel. I was not using it as a model to determine how my barrel in a 30-06 would do. In the modeling software it merely shows deflection from rest which is in all axis’s.
So looking at the graph a 10 minute of arc will turn out to be 0.00092592″ of movement ( 10 X 0.000046296) at the muzzle ( if one will note in post # 9 I annotated exactly what 1 minute of arc value was). If one is to surmise the differing of the 3″ vs the 6″ block then one can assume how much the improvement would be. Or compare the unclamped vs the clamped to tabulate the difference. Now would some caliber cause more or less deflection sure would, but the 308 was chosen to be the standard for this comparison.
Originally the software was chosen to model the 22LR but the movement was so small that it was really not discernible, and it wound up being more suited to center fire.
Like Dr. Kolbe admits if you feed bad values on the barrel contour results in bad data. Has the software author compared this to real observation of barrels, Short answer is Yes, Dr. Kolbe recently sold Border barrels (2012 i think) and is now manufacturing gun smithing / barrel making tooling in the UK. I hope this helps your questions.
- February 27, 2017 at 4:43 pm #33734
If one does the math on the 3″ block, with a 31″ 1.250″ straight dia to muzzle barrel clamped to give a free length of 26.98″ we see 0.00555552″ deflection
Use the same barrel but make the clamp 6″ versus 3″ thus a free length of 23.98″ the deflection is 0.003796272″
That is a 68% increase in rigidity of the barrel with those two length blocks.
Most benchresters would kill for such easy improvement provided they can stay in weight limits.
just for giggles unclamped the barrel deflects 0.00648144″
the 3″ block is approx. a 14% improvement in rigidity compared to unclamped
the 6″ block is approx. a 41% improvement in rigidity compared to unclamped
What does all this math mean really nothing it is just a projection to support an idea until the groups are fired
short range (100-200) Benchresters use short barrels, long range (300 plus) Benchrester use long barrels. Why it works better at their respective ranges.
- February 27, 2017 at 7:10 pm #33739
Also this is posted under his calculator that you might find of interest Popper:
Knowing when the bullet exits the barrel is, of course, fairly critical in determining how the muzzle is changing in angle at this moment in time. The time it takes for the bullet to travel the length of the barrel will be dependent on the cartridge type and barrel length; and is usually between 1.0 and 1.5 milliseconds. There are programs such as QuickLoad which can predict a potentially more accurate value for the barrel exit time.
Steady state standing wave analytic solutions to the equation of motion for transverse vibrations on beams are often held up as “how rifle barrels vibrate”. But in truth, the phase velocities of these transverse vibrations are too slow (compared to the bullet passage time in the barrel) to allow these standing waves to develop during the period of interest. What is required is a numerical model which simulates how a rifle barrel reacts dynamically to the impulsive moment applied to its back end due to the recoil forces. Commercially available “Finite Element Analysis” computer programs that are able to model such events are usually used by car makers to simulate how their latest model will crumple when it hits a bridge or another car, or designers of sky scrapers to see what would happen if an aircraft crashed into their latest design. Consequently, such programs are prohibitively expensive.
But the complexity of the generalised 3D meshes used in such programs is probably not required. Great simplification can be achieved by using a one dimensional array of elements to model the rifle barrel, without significant reduction in accuracy of the resulting dynamic behaviour. In consequence, development of this model for simulating barrel vibrations was started in December 2010 as one arm of an effort to understand the dynamics of a rifle under recoil. The other arm is to actually measure the barrel vibrations in order to verify the theoretical model underpinning this program.
End of Quote
- February 28, 2017 at 12:45 am #33743
Nasa has a Finite Element Analysis simulation of a pipe with air flow at various flow rates, with the ability to ‘attach’ mounts to see what vibration modes exist. Interesting results. I’ve seen vids of barrel whip, most is in the vertical plane, as the mount is under the barrel. If you hit a barrel with a hammer & record the sound you will get the vibration (free or impulse) response of the barrel. The pressure curve rise time feeds that response (like the hammer). Like the laser gun sound from Star Wars – Lucas actually used a guy wire response. But back to the NASA model, it showed the airflow through the pipe actually caused a response that varied by volume flow. If you did a DFT on your data you will find that even harmonics are very low in amplitude (usually), odds have the higher amplitude. Using the wavelength of the harmonics you can predict the distance of the null motion nodes (fps & barrel length). Yes your barrel block dampens the response (more mass). Convolution of your data and the pressure curve proper barrel harmonics data but without the bullet/gas flow portion which IMHO is not insignificant. I’ll send the NASA link if I can find it again.
- February 28, 2017 at 1:59 pm #33754
- February 28, 2017 at 2:00 pm #33755
- February 28, 2017 at 2:02 pm #33756
- February 28, 2017 at 2:03 pm #33757
- February 28, 2017 at 2:05 pm #33758
- March 1, 2017 at 4:05 pm #33793
In post #7 I removed the harmonics graphics, as I really just rather post results rather than discuss NASA FEA (Finite Element Analysis) software ( NISA FEA can be seen here https://www.nisasoftware.com/) vs. Border Barrels version of FEL (Finite Element Lumped) software. Further information can be seen here http://www.geoffrey-kolbe.com/articl…eter_model.pdf for those whom wish to read some bed time stuff. If someone wishes to post the link to either NASA or NISA. FEA simulator that would be welcome I’m sure.
I want everyone to understand I’m NOT attempting to be snod, uppity or even rude. Even though I introduced the computer modeling first, my attempt was to show in a graphical sense the advantage of such devices of a barrel block. The intent of the post was not a computer modeling discussion. Thank you for your time everyone.
- March 1, 2017 at 7:28 pm #33796GoodsteelKeymaster
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Since it’s a discussion of Brux barrels, I’ll chip in the facts as I see them and contribute my opinion.
Brux makes a fine barrel.They have only been in business for 14 years, but they elbowed their way to the top very quickly, and there is no shortage of amazing feats created with their barrels like the .349 600 yard group shot by Rodney Wagner several years ago: http://bulletin.accurateshooter.com/…-at-600-yards/ , or the 50-2X (0.941â€³) group shot by Mike Davis: http://www.bruxbarrels.com/gpage2.html
Yes, Brux is making waves and is in direct competition with companies such as Krieger, Bartlien, Schnieder, and Shilen Select Match.
The external finish is excellent, the bores are hook cut, hand lapped and very very straight. I can detect .005 hook in a bore with my bare eyeball, and with Brux barrels, I can’t really get a handle on which direction they hook which means whatever it is, it’s less than .010 end to end on a 30″ blank. There are many barrels that claim to be hand lapped, but the real test is when I take my borescope and look in the corners of the grooves and see if they managed to get the tooling marks out of that area too. This is important because that is exactly the place where it matters most. Brux handles this as well as Krieger, or Broughton (BTW, this is the real advantage of 5R rifling. It makes it easier and faster to lap the barrels perfectly, and for you to clean them thoroughly).
The turnaround time on Brux is very competitive which is essential to staying on top of the curve with BR and F-class competitors in today’s market. Fact is, many shooters will not buy from a company that makes superb barrels if it takes 6 months to get the product in their hands. Brux can turn a completely custom barrel order in 12 weeks (often less) and the quality is competitive by any metric.
As to barrel harmonics, computer programs are nice, but I’d rather see holes in the paper, and this I have seen a lot of. In my humble opinion, stiffer is better in theory, but a long barrel gives us better use of powder selection and reduces muzzle pressure. These are very good things for a cast bullet shooter because we need all the help we can get. My thought on the bedding block rifle was to keep the barrel length, but get the stiffness of a short barrel at the same time.
Did it have a positive effect?
Sgt.Mike certainly shot tighter groups than the other XCB shooters did, but he was not shooting for speed either, and ran it where the bullets were most comfortable which will produce more precise groups as a matter of course, even if all things were equal. This was his intention from the beginning and directed his selection of barrel twist, so it’s a bit of an apples to oranges comparison to the other barrels and the groups produced by them at higher velocity.
All I can say for sure is that we set out to build an exceptionally precise cast bullet shooter and we succeeded, using a Brux barrel.
I had a good conversation with Ken Liebetrau earlier today and he informed me that Brux barrels are certainly becoming more popular with every match they win, and with several records being broken with Brux barrels in just the last 3 months, if you’re thinking about getting a barrel, it might behoove you to order soon!
- March 1, 2017 at 8:40 pm #33798
……Sgt.Mike certainly shot tighter groups than the other XCB shooters did, but he was not shooting for speed either, and ran it where the bullets were most comfortable which will produce more precise groups as a matter of course, even if all things were equal. This was his intention from the beginning and directed his selection of barrel twist, so it’s a bit of an apples to oranges comparison to the other barrels and the groups produced by them at higher velocity……..
I’ll agree whole heartily Tim, and no I did not get to HV yet
- March 2, 2017 at 12:01 am #33799
Goodsteel;n14618 wrote: ……..Sgt.Mike certainly shot tighter groups than the other XCB shooters did, but he was not shooting for speed either, and ran it where the bullets were most comfortable which will produce more precise groups as a matter of course, even if all things were equal. This was his intention from the beginning and directed his selection of barrel twist, so it’s a bit of an apples to oranges comparison to the other barrels and the groups produced by them at higher velocity….
Agreed Tim absolutely correct.
- March 7, 2017 at 1:19 am #33925tomme boyParticipant
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About cutting the barrel. I thought I read a article about short barrels and the benchrest crowd found that the 19″ give or take a inch depending on caliber was the stiffest and worked the best for tuning.
- March 7, 2017 at 8:13 pm #33945
SgtMike – didn’t mean to get your dander up with my comments. As the L^2/D states, your block merely (as you have stated) changes the profile of the barrel and its harmonics. This is validated by the design of large artillery guns ( like the railroad artillery guns). My comment is the load burn as well as the projectile & gas fps modify the harmonics to a greater extent than your (Dr.’s) program indicates. German’s greatest problem with the V2 was keeping the fuel piping intact.
- March 8, 2017 at 1:04 am #33952
Thank you Popper for your input.
- March 21, 2017 at 4:56 am #34191upinthehillsParticipant
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How about moving the barrel block a little further down the barrel. That might work better with a somewhat longer block, but you might be able to get the barrel to behave like it was much shorter… Does that just make a problem by making the gun have two ends of the barrel ( one with an action on it ) that don’t vibrate the same way?
- March 22, 2017 at 2:11 am #34209
could have sworn I responded earlier lol I guess my age is catching up with me…
I have seen Barrel blocks located several inches away from the action most do not really claim outstanding results. But that does not mean anything outside no results saying that it was the prime area to use the barrel block. It may work great, I do know that a lot of folks whom do use the barrel block usually butt them up against the action. The rule is to have them a bit longer than what I’m currently using. Of those, I have heard a bit better results but not a vast improvement. But in the Benchrest world it does not take much to drive many shooters to a system, method or bullet.
What you mention is a good idea and has several merits in my opinion. If I was to redo it I think I would lengthen the block, but because the system I have works for right now I would just shoot her as she sits. Not for any other reason than LOL I’m lazy and it works and I’d be afraid to mess it up
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