Pressure Works.............

[Michael458]

When we were working with the design issues with the Flat Nose solids by CEB and North Fork we learned that it took 65% meplat of caliber for a solid to be self stabilizing, drive deep and straight. One of my primary concerns was feed/function in a M70. I honestly did not give any thought at all to other rifle manufacturers. As we increased meplat size to over 70%, the M70s began to have problems. A safe bet would be 67% meplat for the CEB #13s, and my friend
at North Fork decided theirs would be 68% meplat.... Both feed and function 100% in M70s. However these bullets will not feed in lesser control feed guns such as CZ and Ruger. Of course a push feed gun you can forget about, even the push feed Winchesters won't feed them. But that was someones else problem, cheap ass rifles........ This was just part of the great bullet wars that were argued for several years from 2006 and even now sometimes within the circles of people who use such bullets. This is the reason you see some bullet manufacturers reduce the meplat size so they feed in cheaper rifles, and disregard optimum performance for it.......

Since this is about pressure works, we did extensive work with strain gages, pressures, and something never done before called barrel strain with the pressure equipment. These studies went into other areas such as a myth called OSR, or Over Stressed Rifling where we turned a .458 caliber barrel down to the thickness of 5 sheets of copy paper and ran over sized steel bullets in it......... another very interesting study.........anyone interested in hearing about these things?

 

[ronn47]

When we were working with the design issues with the Flat Nose solids by CEB and North Fork we learned that it took 65% meplat of caliber for a solid to be self stabilizing, drive deep and straight. One of my primary concerns was feed/function in a M70. I honestly did not give any thought at all to other rifle manufacturers. As we increased meplat size to over 70%, the M70s began to have problems. A safe bet would be 67% meplat for the CEB #13s, and my friend
at North Fork decided theirs would be 68% meplat.... Both feed and function 100% in M70s. However these bullets will not feed in lesser control feed guns such as CZ and Ruger. Of course a push feed gun you can forget about, even the push feed Winchesters won't feed them. But that was someones else problem, cheap ass rifles........ This was just part of the great bullet wars that were argued for several years from 2006 and even now sometimes within the circles of people who use such bullets. This is the reason you see some bullet manufacturers reduce the meplat size so they feed in cheaper rifles, and disregard optimum performance for it.......

Since this is about pressure works, we did extensive work with strain gages, pressures, and something never done before called barrel strain with the pressure equipment. These studies went into other areas such as a myth called OSR, or Over Stressed Rifling where we turned a .458 caliber barrel down to the thickness of 5 sheets of copy paper and ran over sized steel bullets in it......... another very interesting study.........anyone interested in hearing about these things?

Michael, we'll listen and try to learn anything you wish to share with us.

Question:
How do the different lever guns (Marlin, Winchester, etc.) handle the large meplat bullets?
Does the lifting lever help get the cartridge alined with the chamber?
Thanks,
Ron

 

[cold1]

anyone interested in hearing about these things?

Yes! And interpreting pressure graphs too.

 

[JT]

anyone interested in hearing about these things?

Yes! The more I learn from you, the more I realize how little I know. It's quite humbling ...

 

[Michael458]

Question:
How do the different lever guns (Marlin, Winchester, etc.) handle the large meplat bullets?
Does the lifting lever help get the cartridge alined with the chamber?

@ronn47 I have never had an issue at all with the lever guns and large flat meplat solids....... they handle them with ease, Marlin, Browning 71s, Winchesters all.......... and Yes, I suppose the lift lever puts them right in the hole, easy.....I have also used a lot of the really big flat meplat Cast Performance bullets too, no issues there either.........

Since we are talking lever guns, and I love lever guns, will tell you about 50 B&M Alaskan and the various works done with it. I took delivery of the first 50 B&M Alaskan in early 2007. Very simply a .510 caliber Alaskan cartridge taken down to .500 caliber. Then, and even today, there are a lot of very suitable .500 caliber bullets made for the 500 S&W that are perfect in the lever guns, and will hold up even at the higher velocities the lever gun can produce. At the time, I had already taken the 500 gr Hornady Flat Nose soft to the field in a bolt gun, with incredible success at 1850 fps and in addition the 400 Sierra at 2000 fps as well. In 2007 if I could run those two bullets in the lever guns, I did not care about much else at the time. In addition to this I was dead busy up to my eyeballs in the large caliber bolt guns, so the lever gun took the back seat in the bus..........

I had done all the basic load data (no pressures) in a 18 inch Marlin Guide gun. I had the 500 Hornady running 1950 fps and the 400 Sierra at 2100 fps...... the end, good enough for me, on to other things...............

In the meantime we converted a few Hi Grade Browning M71s and played around with the lever guns, but nothing serious.

Very early 2011 Layne Simpson took a serious interest in the 50 B&M Alaskan and requested some assistance doing an article. I agreed, and it was decided that I send him a couple of guns for the article, some loaded ammo, some dies and bullets and what have you so he could do it right. By this time I had decided I really like the pistol grip version of the Marlin much better than the Guide gun version because of the stock configuration, the Guide gun having too much drop in the rear, which caused serious muzzle flip. The pistol grip version much more in line with the bore, easier to control, like the M71s........ I had a new gun in the rack with the pistol grip, that I had originally built to sell, but decided to send it to Layne along with one of the Hi Grade M71s for the article.

At that point I thought maybe I should test fire this gun before sending it, how would it look to send Layne something that might not function properly? Off to the range with some of the 500 gr Hornady loads at 1950 fps..................Fired the first round, and the damn thing locked up tight!!!!!!!!!!!!!!!!! OH CRAP....... this is not good.................Experienced the same with the 400 Sierra loads...... Ok, We have a Problem........... Not my first rodeo, and I had seen lever guns do this, so I should have known better than to base my knowledge and data on one Marlin Guide gun. The M71s handled the loads fine, but all Marlins are not created equal...........

I very quickly put a strain gage on the gun and went to work. After a couple of weeks I had things running smooth, pressures in the Pistol grip Marlin would run up to 45000 PSI before running into issues, and that is how we rode it out. The velocities of the 500 gr bullets dropped to 1850 fps and around 1950 fps for the 400s.............. Removed the gage, sent the two guns to Layne, he did the article, very nice one, loved the guns and the cartridge, and had one built for himself.

This is Laynes rifle, he and I argued about the barrel length on his..............

After getting the Marlin back from Layne, I put another gage on it and really did some serious work with it...........this gun proved to be the perfect rifle to do the pressure work with, when it hit 45000 PSI it started talking to you, every time it would let you know it did not like something. All the current Pressure Load data was taken with this gun. Today, these loads work across the board in every rifle they have been used in. Layne and I worked together on many of these projects. One for the Marlins was with the 300 Hornady Flex, which seated and crimped in a standard length cartridge is too long for the Marlin actions. I ended up shortening a small sample of cases to 1.970 inches so we could use the 300 Hornady Flex in the Marlins, I think Layne even wrote about it later in another article. At 42000 PSI we could run the 300s at 2400 fps.

In addition to doing the Pressure data, I also designed several bullets specifically for the lever guns from Cutting Edge Bullets and North Fork Tech. These bullet designs also carried over to 45/70s as well. Recently updating some of the 45/70 data even on this thread as well.................

The larger action M71s can handle just a bit more pressures than the standard 45000 PSI set for the Marlins. I can't tell you exactly, but would guess around 50000-52000 PSI upper end.

Bullets designed for the lever guns have to have a much shorter nose projection, seated deeper in the case to reduce overall length to feed and function. All these are designed to work in the shorter action Marlins.

The 50 B&M Alaskan thrives on H-4198, IMR 4198, H-322, RL 10X and RL 7.................

 

[Michael458]

Yes! And interpreting pressure graphs too.

I think I spoke about the difference in the two Softwares and reports between RSI and Oehler in the other Pressure thread, so I won't go that much in depth here. YOU CAN LEARN A LOT by looking at the various pressure curves, and the RSI software used in the Pressure Trace units, is light years ahead of the Oehler software and reports. Oehler is still using 1980s reports it appears. The Units are incredible What you see is what You get pressures, but the software is not so damn good...............

Here is a Oehler report showing the pressure curves, not shit you can learn from looking at the actual pressure curves.........

And an example of the RSI Pressure curves and reports...............

Keep in mind, Oehler is the Industry Standards........... If you are looking for pressure data from any major manufacturer, bullet, powder, load data book, any of them, they are using Oehler...........

I use both, but I do admit the last couple of years I have been very lazy and just hook up the Oehler, as most of the time now I am only looking for that number................

With this stated, then we will move on to look at how some cartridges behave and some of their various curves........

 

[Michael458]

The basic pressure curve peaks on average between .3 and .5 milliseconds, then afterwards it starts to go down and most of the time the bullet exits at 1.25 to 1.5 milliseconds. Most curves show it still has some pressure at the exit, 20000+ PSI. And I believe that is mostly correct, as the first Barrel Strain tests we did in double rifles (strain gage 4 inches back from the muzzle) we used full power loads, and at the exit strain gage we were getting readings of 20000-25000 PSI.

The higher pressure loads will peak sharper, and most of the time faster than the lower pressure loads that are more of a HILL, than a sharp peak. The Pressure curve in the previous post of the 416 B&M is fairly typical of these cartridge, this Trace was rather mile at 55000 or so, as pressures increase that peak would get sharper.

With the RSI Software, on most of the curves I have these set to view between 1.5 milliseconds and 2 milliseconds depending on the cartridge, most will be at 1.5. Naturally the shorter frame you work with the sharper the peak would seem as well.

Different powders within the same cartridge can have different curves and peaks as well, we all know all powders are not created equal, slow, faster, and some in-between, all will show different curves and peaks..........

I apologize, I only have a limited number of Pressure Trace Peaks that are loaded and converted to Jpg for viewing. I hope I have enough to be able to explain some of these things I am talking about. I have literally probably 1000s of tests, but only a select few that have been printed, copied, converted to jpg so they can be loaded..........

Here is a sample of 500 MDM, a high pressure cartridge max at 65000 PSI. However, the traces we are looking at do not approach that pressure, this happens to be a few of the Blending tests I have done......You will see it peaks at less than .5 milliseconds..... In some cases you will see a small bump at the end of the trace, sometimes this is an actual pressure bump caused by a particular bullet just before exit, other times the bump is much larger, sometimes overtaking the actual peak pressure, this is without doubt not true, and would be an electrical connection or gage problem.

Here is a typical screen photo of a double rifle trace with the slower longer HILL type peak.............Common with lower pressures, and the bigger Nitro cartridges........With Double rifles we don't want to exceed 45000 PSI

In this case with 500 Nitro we see how two different powders give a different pressures with the same results. Nearly 2100 fps.............

And V-N550. And if you notice the velocity they are near the same. In this case we as shooters would definitely go with the WW 760 at lower pressures...........

Sometimes, and recently, I see people ask "Why hand Load".............. You see those mostly nice loads and curves posted........ here is a Norma Factory Ammo test............ Look at this crap.............

And this Factory Ammo.....

 

[Michael458]

I wish all loads and curves would look like these...............

Sometimes its not really your fault in hand loading, it is a crappy bullet that is inconsistent........... these were some crappy bullets............

Here is a chart of a test done for Filler materials....... all the same load, and bullet, just different Fillers.............

 

[Michael458]

This is a prime example of an Connection issue with the strain gage..............

 

[Michael458]

Cutting Edge asked if I would do some 338 Lapua work for them, of course I agreed, so they sent rifle and they sent the loads they wanted to test............. I used both Oehler and RSI Pressure Trace to do the work. I found the 338 Lapua gave some very odd curves and peaks.........

 

[cold1]

Cutting Edge asked if I would do some 338 Lapua work for them, of course I agreed, so they sent rifle and they sent the loads they wanted to test............. I used both Oehler and RSI Pressure Trace to do the work. I found the 338 Lapua gave some very odd curves and peaks.........

Are these curves similar to other bottle neck rounds with similar burning powders?

 

[BatteryOaksBilly]

Don't you have 45 Colts to load????? I Think you DO!!!

 

[Desolo]

I do enjoy these posts, Thanks for showing us this stuff!

 

[Michael458]

Are these curves similar to other bottle neck rounds with similar burning powders?

No, none that I have ever seen before. Extremely sharp rise in the first .1 millisecond, followed by the slow rising curve.... not normal...... I am not sure if that is the nature of the cartridge and Retumbo, but as I recall it was indicative of the cartridge overall even with other powders.......

 

[Michael458]

Don't you have 45 Colts to load????? I Think you DO!!!

Ya Boss, I s on it.............

 

[ronn47]

Ya Boss, I s on it.............

 

[Michael458]

Don't you have 45 Colts to load????? I Think you DO!!!

You seriously need to do a SEARCH.........This is a photo taken of the first batch of really hot 45 Colt I loaded for you. The FA cylinder is so short, I kept the CEBs for the lever gun, and had to load some more for you seated deeper for the FA gun. In the background, in the blue tray, is a batch of 300 gr Hornady, seated to the cannelure, they fit the FA gun. I am going to look in the box in the range room that has the longer loaded CEBs I kept, but I am pretty damn sure I might have sent these Hornady loads home with you since they would fit in the FA Cylinder............ If I don't have them here, then you have to have these! They are 45000 PSI and will blow a Colt or similar all to hell...........

 

[BatteryOaksBilly]

K Den.......I'll look tomorrow...I should be able to see REEEEEL good.

 

[Michael458]

K Den.......I'll look tomorrow...I should be able to see REEEEEL good.

Yeah, you will have NEW X Ray Vision, and will be able to find all that ammo I loaded over the years that you put away, somewhere.....................You will "See" me soon...............

 

[Michael458]

Barrel Strain............

What in the world is "Barrel Strain".............. Barrel strain is defined as the amount of strain, stress, or stretch of a particular bullet as it passes down the barrel. For most common purposes it has very little meaning to most of us. The biggest factor that barrel strain can have is direct pressure with a bullet. An oversized bullet that is tight in the barrel will cause more pressure, common sense. But to others, barrel strain can have other meanings, and more far reaching factors.

Double rifle shooters are very concerned about barrel strain, and most do not even understand or know the term itself. Double rifles present a different problem. Barrels are soldered together and it is an extremely tedious and expensive process to get two barrels to shoot together, and then lock them down after you achieve this. Any bullet going down a barrel stretches and expands the barrel the entire time it is going down. The more that stretches those barrels, the more strain put on the solder that is holding it together. When modern CNC Monolithic bullets came on the market, double rifle shooters blamed these bullets for the very infrequent occasions that the barrels would separate. Soon myths were perpetuated that you could not shoot monolithic bullets in a double rifle, it would cause damage to the barrels, separate barrels and even cause OSR. OSR? Over Stressed Rifling. Many years ago, a double rifle shooter noticed strips on his barrels when held up to the light in a certain way. The stripping matched the rifling in the barrel, and from this a total MYTH was started that monolithic bullets would press the rifling through the steel of the barrel and show on the outside!

OSR is a total myth and rumor, and is still perpetuated by ignorance even today. In the next part of this discussion in Pressure Works, we will address OSR, and bust the myth completely.

Barrel strain is very important however with these double rifle guys. I am not a double rifle type of chap, I don't care for them in the least, they are a real pain in the ass. The crowd that I used to run with however are sometimes nuts about the damn things, and it is all about "Nostalgia" of hunting in Africa. They try to justify all the reasons for a double rifle, but in the end its all about Nostalgia and hunting like they did in the old days.... Blah Blah Blah............To me, double rifles are far inferior, and far less versatile than your Winchester M70 big bore........ You just can't shoot a variety of ammo or bullets in one, its normally regulated at 50 yards for 1-2 loads and bullets, and that is all you get.

I have a very good friend from NC, Sam Rose. Sam has been a test partner and friend for nearly 15 years now. We have tested everything you can imagine, Sam was instrumental in working with me to develop the CEB and North Fork bullets we all shoot today, we have tested new cartridges, bullets, load data and all manner of things, and one of the most important works in which we have embarked upon is the double rifle work we have done together. Sam has the double rifle bug, and he loves them. So all the double rifle work we did was instigated by Sam. I love discovery, and firearms science, so it did not matter to me what we were working on, it was very exciting and a great learning experience, and not only that, what we did was decisive, proven, and had never been done before, or since........... Much of the work we did on this stands today as accepted science and used by various manufacturers.

Sam and I first met we were working with different bullets, mostly solids for big bores. One day he wanted to test one of his mighty 577 NE loads, 750 gr Round Nose Woodleigh. Sam left very disappointed that day, as the bullet failed miserably in penetration. In fact, it turned sideways and was only able to penetrate 14 inches straight. This set him on fire, and from that point forward we were concentrating efforts to design a better solid and making them work in double rifles as well. Long story short, we developed the right size meplat and nose profile, and now it was time to test this in double rifles...........

We started working with a 470 NE to begin with, set up a gage to do Chamber pressure. While doing this, we decided we could put a stain gage 4 inches back from the muzzle, and measure how much the barrel expanded at that point by the passage of a given bullet..................This would measure what we came to define as Barrel Strain.

Our first work in this area we used full power loads. At 4 inches back from the muzzle we were still getting some effects from the chamber pressures. In later tests, in other calibers, we reduced the loads down to where chamber pressure did not make it to that point, and all we received was the passage of the bullet at the strain gage. It was a learning process............

In the world of Double Rifles, Woodleigh used to rule. Everyone considered the Woodleigh Soft Point a safe double rifle bullet, and because of its design, Round Nose, it held nostalgic value to those guys as it resembled the old original Kynoch bullets. In all tests, we considered the Woodleigh Soft as the "BenchMark Bullet"............... We test the Woodleigh and all strains below the Woodleigh Soft would be considered SAFE, and all strains ABOVE the Woodleigh Soft considered a danger or cause for possible damage to the barrels.

There are a few ways to REDUCE barrel strain. The common one used by bullet manufacturers is by reducing the diameter of the bullet. The other is reducing the bearing surface that is actually engraved by the rifling. Materials also can be a factor as well.

I ranked the bullets tested from LOW to HIGH....... here is the work done on the 470 Nitro, reminded that these were full power loads, all at 106/IMR 4831 regardless of bullet. Also note that in this data bullet diameter was not recorded, we were still learning.

Sam and I concentrated our efforts at reducing barrel strain with the bands, and by reducing bearing surface. While keeping the bullets at caliber diameter. Here is the data, with measured bullets ranked from low to high. Keeping the Woodleigh Soft as the BenchMark to go by. As you note, Woodleigh and a few others reduced diameter of their bullets.

The CEB and Or #13 BBW bullets are the bullets that Sam and I had direct design of the bands, some of these ere only 2 band bullets, others 4 band.............Of course the BBW #13 Nose profile and meplat size are the same as todays CEB Safari Solid line...........

The lower the barrel strain the better. And in all the 470 Nitro tests we were still getting some effects from full power loads and chamber pressures, as you will see in later tests with 458 and 510 calibers, in which we reduced the load to eliminate that factor.......... In the end, the various ranking of different bullets was much the same as what you see above............just lower numbers..........

To be Continued.........................

 

[OldNascar]

Lead bullets caused more barrel strain than all those tested?

 

[Michael458]

Lead bullets caused more barrel strain than all those tested?

Yes, we were just as surprised and baffled as well. I mean lead is supposed to be soft on barrels right? First, most lead and especially for rifles is fairly hard, and above that it is oversized by .001 normally as well....... We also felt like there was a possibility it was slugging up tight as it went down the bore, possibly causing the higher barrel strain as well......... Perfectly honest, that is just theory, and not something proven. It was the same case in .458 caliber as well. Cast Lead gave higher numbers than the benchmark bullet.

I decided that the bullet really did not know what sort of barrel it was going down, either double rifle or bolt gun or other, really didn't matter in this case. We are measuring the amount of barrel expansion at the point where the gage is connected, nothing more. I put a gage on a 20 inch 458 B&M, again 4 inches back from the muzzle. And this time I tested loads that did not effect the forward barrel gage, from rear chamber pressures. I used the same load regardless of bullet, 56/H-322 and it gave anything from 1800 fps to just over 1900 fps from 300-500 gr bullets.

We were able to test all sorts of various bands as well. Some 3 bands, and one or two of those bands under caliber and all sorts of variations of. In the end, it really did not make much difference, if any between 3 bands and 4 bands. The standard 4 band #13 Design at full caliber was well under the Benchmark and within many of the 3 band versions. We did test a 500 gr Barnes banded that was very very low, in fact it came in the lowest of all the bullets tested, but it was way undersized at .456. I also ran one .416 caliber bullet down the bore too, just to see what would happen, and of course that was very low too........This served to get a very bottom end number in which to compare.

We later did 500 NE Barrel Strains as well............. And pretty much the same results overall.............At no time were CEB or North Fork bullets over the Benchmark, and in all tests they were all very much under most common available bullets. Therefore being deemed "SAFE" in double rifles.

We paid very close attention to each of the gage curves, which told us quite a bit. Very typical of most bullets that were common jacketed bullets with full bearing surface you get a very sharp steep climb at the passage of the bullet, as you see in the following examples......

Bullets that gave the lowest strain numbers looked like this, very rounded, slower rise.............

And a Cast Bullet curve, and shows one of the reasons we believed these might be slugging up in the barrel further down as it passed.......???? But that is just theory.........

And this will conclude this study, I think you get the jest of the matter.............. Next, what might be very very interesting to you is the OSR study........ Over Stressed Rifling MYTH. In this study we ended up shooting a barrel that had a thickness of 5 sheets of copy paper at the muzzle!!!!!!!!!!!!!! Yes, barrel thickness was the same as 5 sheets of paper at the muzzle.....................

 

[Michael458]

Many years ago a Myth got started by double rifle shooters. It centered around one particular double rifle that had what appeared to be striping down the barrel, viewed from the outside when held up to the light in just the right way. It was reported that you could not feel anything, or could not even photograph it, only when held up looking down the barrels in the right light could you see it. It was also reported that this fellow had fired a few Barnes Monolithic bullets in his gun. This was when Barnes first came out with some of the solid mono bullets. And the story continues until it evolves into the barrels being damaged by these very hard bullets, and in fact the rifling being pushed through the steel barrels and appearing on the outside...................then along came the term OSR......... Over Stressed Rifling................

This event even made it to one of the books written by a so called expert on Double Rifles, along with warnings about shooting these type bullets in double rifles.................

10-15 years ago this myth was making the circles heavy in the double rifle world, and by damn it was "gospel" at that time. You simply could not shoot mono bullets in these guns, it would cause the rifling to push completely through the steel barrel, ruining the rifle................ You had to shoot only approved and safe bullets for double rifles........

Push the rifling through to the outside of a steel barrel? Really?

I am no metallurgist by any stretch of the term, however, I really had to question this. And far more knowledgeable and talented than I am, my buddy Sam Rose decided we would tackle this myth and get to the bottom of it. Of course, with him being a huge double rifle fanatic, it was more important to him in that aspect...............Sam is very talented working with metals and tools, has his own lathes and such as that. He bought a .458 caliber barrel, chambered it in 458 B&M, and we put it on a Winchester M70. He had turned this barrel down to THIN to begin with, and as we continued to test, he kept thinning it........... We had all sorts of wires hooked up to this thing measuring every aspect we could think of.
We used the same loads that I was using to do the barrel strain tests, so nothing extreme pressure. The gun was very light however, just a bit over 4 lbs, so we strapped it down in a lead sled to do the work, and to keep it from jumping around and jerking the wiring loose.........

After every shot we measured the barrel to see if it had expanded and recorded that. We did get some expansion caused by heat, but soon as the barrel cooled it went back to original dimensions......

Barrel was highly polished, if we had been able to push the rifling through to the outside, we could have seen it .

In our first tests we had two sections of barrel thickness........ The small section of barrel had a wall thickness of .05675 inches. We fired a variety of bullets in the first test, we experienced no change in the barrel.

In the second test Sam had thinned the barrel down considerably to .03735 wall thickness. No production rifle made has a barrel this thin. Again, no OSR, No change in barrel expansion, nothing.....................

Continued....................

 

[Michael458]

For the Third and final OSR tests, Sam turned the barrel down to a wall thickness of .0225 inches. Extremely thin.......................

And, to continue EXTREME.....> Sam turned down some over sized brass and even STEEL bullets to shoot down the bore........

When we completed the test we cut a section out so it could be inspected better.....

I would think that after all this if OSR was anything but a myth it would show up. Over Sized STEEL bullets and a barrel that is the thickness of 5 Sheets of Copy Paper and NO OSR? OSR is BULL CRAP....................

Here are the results of the 3 tests. In the very end we shot 2 rounds loaded with Dacron to see if we could blow something up. We did not. But, we had two bullets and the barrel was HEAVY OILED and it caused a permanent expansion of the barrel by .0008 inches......... OIL in the barrel may not be your friend???????????

OSR is a myth created by ignorance............. There is no science that can prove it exists..........

 

[OldNascar]

Thanks for the study. To me the ideal study would have been of the rifle in question with various projectiles fired through it’s bore. Without molecular duplication of the barrel with the stripes the test is a little suspect due to the unknown differences of the barrel tested and those of the double rifle.

 

[Frack N Cylons]

As always, a very interesting read. I’ve always wondered why, in my old Para 45, I can see the rifling coming through the barrel finish. I can’t feel anything there. It has never concerned me, just curious.

This thread reminded me of it. Is it akin to what any of the double rifle fellows were seeing?

 

[Catfish]

That's probably an artifact from the stresses of creating the rifling to begin with. How do they do that anyhow?

 

[Michael458]

To me the ideal study would have been of the rifle in question with various projectiles fired through it’s bore. Without molecular duplication of the barrel with the stripes the test is a little suspect due to the unknown differences of the barrel tested and those of the double rifle.

Unknown person, unknown rifle, and the entire matter was hearsay.........Ideal? Maybe, but due to circumstances impossible.

However, you are close............Double rifles are made all over the world, and many made in Europe. Steels, rifling, blueing are all subject to differences in treatment................. Doubles are extremely expensive, low end at $10'000 and no upper end, I have seen $250'000 doubles and more in some cases........ Common price for a really good double is around $20'000-$25'000.

Some years ago Sabatti hit the market, and going for $5000 or so. I don't remember the entire story on those, some were good, some not so good. In some cases they regulated the barrels by manipulating the inside crowns, actually reaming one side or the other.... not good at all, as you can imagine this can destabilize a bullet. But it was done none the less......... Sam ended up with a 500 Nitro Sabatti without the crowns being ground on. It was actually a pretty decent gun, shot very well. We used this gun to do load data, barrel strains and we shot the right side barrel a hell of a lot. In the end we had fired this barrel well over 1000 rounds doing test work, I even used it to do some powder blends. I kept it here for months on end, shooting and testing various things with 500 NE.

Sam pitched in one day and we were playing with the gun, and he noticed something odd with the right barrel. Holding it up to the light in a certain way, one could see some stripping down the outside, very faint, and barely visible. He nearly passed out, and was afraid that OSR was actually REAL................You could not feel anything, you could not measure anything on the outside, just by holding it in a certain light could you just see the faint outline of some striping.

Not long after this, the gun went stupid and would not regulate. The solder holding the barrels together came loose, and the middle rib came off. Close inspection of this showed that it had only been spot welded, or soldered together, and not a full run down between the barrels, a cheap put together, and more or less might expect something like that. The rifle was sent in, put back together.

Our "theory" on this striping was that it was caused by heat. Now its been some years, so I may have this wrong, but I believe that Button Rifling is done by pulling a cutter down the barrel using hydraulics. As I understand this puts the steel under immense strain. It is a cold forming process at tremendous pressures. Afterwards the barrel has to be stress relieved by heat treatment. This is a lot of variables being introduced, a particular batch of steel, its hardness, size, how fast the button is pulled and the stress relieving process. Probably slightly different in all cases...........

Could this process change the molecular properties of the area where the grooves are cut?? And, if so, if you put a high polish blue on that barrel, and double rifle barrels are normally thinner than normal bolt gun or other barrels, and then this barrel gets heated up during extensive test sessions, could it cause this striping we might see? What we do know for a fact, on what we have seen, is that the "Rifling" is not pushing through the steel to the outside. We do not believe that is possible, not by shooting a bullet down the bore, even over sized STEEL bullets. What we do believe is possible is the molecular changes made in the steel after engraving the rifling in the barrel, and the way that is heated and stress relieved afterwards, and the possible over heating of the barrel during test work or shooting exercises....... We believe it is possible to see striping because of this.

It is almost a non event. We know it does not effect the rifle in any way that we can find. Purely a visible issue, extremely rare, and not actually limited to double rifles. A good friend of ours in TX reported a factory Ruger bolt gun that had this visible striping down a high polished blue barrel. It was new, never fired. So there is no way that a bullet passing down the bore could have done this.

Remember, the concern and issue of this is shooting monolithic bullets causing the rifling to push through to the outside of the barrel......... THAT is what has been claimed.

After this we never gave it much more thought. At points in time we see some folks mention OSR, but no one can show anything, everything is hearsay...............

The most interesting thing about the entire test to me was shooting the over sized bullets in the thin barrel.... remember, wall thickness of 5 sheets of copy paper...... thin as P**S on a rock I reckon.............

 

[OldNascar]

One of the aspects of viewing this striping dilemma is barrel steels are fluid and once looked at in that regard the displacement by button rifling verses cut as well as stamping can be confused with stress/strain involved in firing the rifle. Plenty of ‘movement’ is going on in fluid steels whether stamped, impressed, hammered and without a limited amount of movement the steel will not return to it’s initial structure if not over stressed beyond it’s yield strengths. I doubt the stresses on the barrel by a banded bullet would come close to exceeding the barrels abilities.

As a side note I agree with the advantages of the bolt gun as long as the cartridges stay short enough for a shooter’s ability to operate the bolt properly. Once pass the limit the multiple barrel gun has it’s merits.

 

[Gator]

Yes, we were just as surprised and baffled as well. I mean lead is supposed to be soft on barrels right? First, most lead and especially for rifles is fairly hard, and above that it is oversized by .001 normally as well....... We also felt like there was a possibility it was slugging up tight as it went down the bore, possibly causing the higher barrel strain as well......... Perfectly honest, that is just theory, and not something proven. It was the same case in .458 caliber as well. Cast Lead gave higher numbers than the benchmark bullet.

I decided that the bullet really did not know what sort of barrel it was going down, either double rifle or bolt gun or other, really didn't matter in this case. We are measuring the amount of barrel expansion at the point where the gage is connected, nothing more. I put a gage on a 20 inch 458 B&M, again 4 inches back from the muzzle. And this time I tested loads that did not effect the forward barrel gage, from rear chamber pressures. I used the same load regardless of bullet, 56/H-322 and it gave anything from 1800 fps to just over 1900 fps from 300-500 gr bullets.

We were able to test all sorts of various bands as well. Some 3 bands, and one or two of those bands under caliber and all sorts of variations of. In the end, it really did not make much difference, if any between 3 bands and 4 bands. The standard 4 band #13 Design at full caliber was well under the Benchmark and within many of the 3 band versions. We did test a 500 gr Barnes banded that was very very low, in fact it came in the lowest of all the bullets tested, but it was way undersized at .456. I also ran one .416 caliber bullet down the bore too, just to see what would happen, and of course that was very low too........This served to get a very bottom end number in which to compare.

We later did 500 NE Barrel Strains as well............. And pretty much the same results overall.............At no time were CEB or North Fork bullets over the Benchmark, and in all tests they were all very much under most common available bullets. Therefore being deemed "SAFE" in double rifles.

We paid very close attention to each of the gage curves, which told us quite a bit. Very typical of most bullets that were common jacketed bullets with full bearing surface you get a very sharp steep climb at the passage of the bullet, as you see in the following examples......

Bullets that gave the lowest strain numbers looked like this, very rounded, slower rise.............

And a Cast Bullet curve, and shows one of the reasons we believed these might be slugging up in the barrel further down as it passed.......???? But that is just theory.........

And this will conclude this study, I think you get the jest of the matter.............. Next, what might be very very interesting to you is the OSR study........ Over Stressed Rifling MYTH. In this study we ended up shooting a barrel that had a thickness of 5 sheets of copy paper at the muzzle!!!!!!!!!!!!!! Yes, barrel thickness was the same as 5 sheets of paper at the muzzle.....................

Your data collection / management is very impressive. I learn things from you that I didn't even know was even something you could learn.

Thank you for the education.

.

 

[Michael458]

Many of the tests we have done here have little interest to most, some of which have no real interest to me either, other than the pure fact of learning something, or new discovery. The above mentioned OSR test really got far more attention than it deserved, with the exception of the fact that Sam and I were both running into this and having discussions with double rifle shooters about it. The barrel strain tests did help with the designs of the bands and reducing bearing surface without sacrifice of other factors such as accuracy. These tests also helped a lot with reducing chamber pressures as well. We very quickly learned that by reducing bearing surface, we also reduced peak pressures. When you think about it, its just common sense........and logic.

I don't get heavily involved in these sort of things any longer, its just too time consuming, and these days I can't work up the interest or desire to do as much.............

I get requests about projects all the time, most I steer in other directions............

On occasion something peaks my interest and I enjoy working on it. But it always seems that one thing leads to another, and nothing ever ends up easy as you think it will in the beginning.......................