Chicken or egg? Cartridge pressure, case specs or gun specs?

[reddog81]

Whether or not the brass is the weak link depends a lot on the gun. For low pressure revolver rounds the brass could typically handle much higher pressures than the gun can. You could load .38 Special brass to .357 Magnum pressures and shoot all day in any modern .357 Magnum gun and the brass wouldn't cause any issues. Eventually you'd run into the same problems with the .38 Special brass as you would with .357 brass - loose primer pockets, sticky extraction, etc.

You could probably load 45 ACP brass to 30,000 PSI and shoot all day without issue in the appropriate gun. However in the wrong gun it would batter the gun to pieces, and an out of battery discharge is going to be a lot more spectacular at 30,000 PSI vs 20,000. Additionally, that out of battery event is probably going to be a lot more likely in a gun that has been abused and tinkered with.

 

[Slamfire]

For low pressure revolver rounds the brass could typically handle much higher pressures than the gun can.

The brass will always be the weak link. Quarter hard brass runs at 44,000 psia at yeild. That is, an square inch starts to give way, like taffy being pulled, with a 44,000 pound load.


But there is not a square inch of brass in any sidewall or case head. Bolt lugs are about 1/2" of steel, you can multiple the shear cross section and come up with a shear load, that is not too difficult.





Regardless steels, even WW1 era steels, 50,000 psia yeild is pretty low end. This data is from the 1920's, showing various heat treats of plain carbon steels compared to nickle steel alloy. The point is, a little nickle really increases the yield, and what is not shown, is the fatigue lifetime. Alloy steels have much longer fatigue lifetimes. Yield is the important number, everyone is fixated on destructive tests, big badda booms are interesting in all, but out side of comic relief from exploding animals and cans, if you want to use the item more than once, yield is the important number. Loads are kept below yield. Once a steel part stretches permanently, it is time to replace the part. Not only are loads kept below yield, they are kept well below yield, due to fracture fatigue. How many cycles to failure do you want? Load up a part exactly to yield and don't be surprised if the number is less than ten, depending on the material.



These are from AMCP Pamphlets, one of these days I will have to annotate with the pamphlet number







The M52 S&W, so much case head stuck out of the chamber that shooters I talked to, told me you could only fire the things with low pressure target loads, or the case head would blow. A typical load was a 148 LWC with 2.7 grains Bullseye.



I keep on encountering Hatcherism and Ackleyism in the shooting community. Hatcherites believe the case is strong and the action is weak, Ackley built on this to claim that straightening a case allowed a reloader to increase chamber pressures by at least 20,000 psia. Both of these ideas are nonsense. The cartridge case is a gas seal. Think about how this case functions. The only thing that is holding pressure is a tiny amount of the case head.



Look at this sectioned case. The case will rupture if the case head sticks out of the chamber above the primer pocket.



I want to expound on the gas seal aspect. Recently I had an O ring blow out of my air compressor. O rings are not strong, they must be supported or they will rupture, or blow out. Just look at the end of compressor fittings, they are recessed to keep the O ring in place, the O ring is supported top, bottom, sides. An O ring is too weak to hold any pressure, but, the system works when the O ring is fully supported.

 

[reddog81]

My post mentions low pressure revolver rounds i.e. 32 S&W, 38 S&W and such and your post is all about rifles and the S&W model 52. Anyone who owns a model 52 would know that the gun only runs on light wadcutter loads.

In the 1920's heat treatment and the use of various alloys became much more common. However there are still guns around from periods prior to the 20's. I'd be willing to bet there are a number of guns in my basement that would be rendered unusable after a few 44,000 to 50,000 PSI loads.

 

[denton]

Just one small footnote to the excellent discussion of steel properties: The time it takes to conduct heat out of the steel in the quench bath is very critical for carbon steels. If the steel is thick, the center will necessarily be less hard than steel near the surface because the center cools less rapidly. When you go to a richer alloy, like nickel, the speed of the quench is much less critical.

It is quite possible that improper quenching was why some of the early Springfield 1903s failed. The military switched to a richer alloy, and apparently the problem went away.

Not long ago, we did a project for a very well known manufacturer. They had hardened dies made in one plant being used in the other. The two plants were practically at each other's throats over faulty performance of the dies. We showed that the 52100 high carbon steel (purchased from Eastern Europe!) was not being properly quenched, and that the problem was solvable by only filling alternate cells in the quench basket. L6, which is higher nickel, worked just fine with full baskets. After all, it turned out that one of the impellers on the quench bath was installed backward. Turning that around made much better dies.

If only they had paid better attention to the lessons of a century ago!

 

[Slamfire]

It is quite possible that improper quenching was why some of the early Springfield 1903s failed. The military switched to a richer alloy, and apparently the problem went away.

The Army Arsenals were a mess. Hatcher mentions that there were no temperature gages in the forge shops. The only pyrometer I found, prior to 1918, was used for springs. A bud of mine claims there is no evidence that they even used pyrometric cones to calibrate anything. From Hatcher's short description, eyeballs were used to determine temperature, and I will bet, eyeballs were used to judge temperatures from forge shop to heat treating ovens. Don't assume that the Army Arsenals had anything, were at any level of modern technology, they had been underfunded since the Civil War ended. The most likely cause of the low number problems, as mentioned by Hatcher, was steel burnt because temperature gauges were not being used. And it was not because the workers did not use the temperature gauges they were provided, they were not provided temperature gauges.

The process controls were awful. Watertown Arsenal wrote a 1917 vintage report. They report a M1903 blowup and the rifle made it out of the factory, passed proof, and the receiver was not heat treated. That shows a factory floor out of control, chaotic process flows, etc, etc.

Springfield Armory kept using the same plain carbon steels up to the 1920's. I was told that they bought a huge amount and still had a pile left over after the war. The nickle steel receivers were initially Rock Island receivers, and once they used up the nickle steel Rock Island receivers, SA used the RIA nickle steel stockpile. The plain carbon steel stockpile lasted until 1927. There was nothing going on for a long time after WW1. The factory went from tens of thousands of workers to hundreds in the space of a year when the war ended. The big change was made during WW1, it was a complete do over of the organization, factory flow, machinery, process controls in 1918. I have read the SA reports of the time. SA hired ten full time staff for a "metallurgical" department. Ten people are expensive, there was some big changes going on. They shut the factory down for a month, in the middle of a damn shooting war!! Does anyone understand how serious that is, to shut a service rifle factory down in the middle of a World War? I think SA completely overhauled everything and brought their factory up to WW1 standards.

 

[denton]

The Army Arsenals were a mess. Hatcher mentions that there were no temperature gages in the forge shops. The only pyrometer I found, prior to 1918, was used for springs. A bud of mine claims there is no evidence that they even used pyrometric cones to calibrate anything. From Hatcher's short description, eyeballs were used to determine temperature, and I will bet, eyeballs were used to judge temperatures from forge shop to heat treating ovens. Don't assume that the Army Arsenals had anything, were at any level of modern technology, they had been underfunded since the Civil War ended. The most likely cause of the low number problems, as mentioned by Hatcher, was steel burnt because temperature gauges were not being used. And it was not because the workers did not use the temperature gauges they were provided, they were not provided temperature gauges.

The process controls were awful. Watertown Arsenal wrote a 1917 vintage report. They report a M1903 blowup and the rifle made it out of the factory, passed proof, and the receiver was not heat treated. That shows a factory floor out of control, chaotic process flows, etc, etc.

Springfield Armory kept using the same plain carbon steels up to the 1920's. I was told that they bought a huge amount and still had a pile left over after the war. The nickle steel receivers were initially Rock Island receivers, and once they used up the nickle steel Rock Island receivers, SA used the RIA nickle steel stockpile. The plain carbon steel stockpile lasted until 1927. There was nothing going on for a long time after WW1. The factory went from tens of thousands of workers to hundreds in the space of a year when the war ended. The big change was made during WW1, it was a complete do over of the organization, factory flow, machinery, process controls in 1918. I have read the SA reports of the time. SA hired ten full time staff for a "metallurgical" department. Ten people are expensive, there was some big changes going on. They shut the factory down for a month, in the middle of a damn shooting war!! Does anyone understand how serious that is, to shut a service rifle factory down in the middle of a World War? I think SA completely overhauled everything and brought their factory up to WW1 standards.

Very interesting post. Thanks!

So sort of like a lot of the clients we work for, then?

 

[Slamfire]

Very interesting post. Thanks!

So sort of like a lot of the clients we work for, then?

Springfield Armory had rifles blowing up well before an incident with an Ammunition Manufacturer that forced them acknowledge they had a problem. Until then, they could bully the simple Soldiers and Shooters, but when they ran into a group with real Metallurgists, and it was a Commercial manufacturer who could go to a Congressmen, the cat got out of the bag.

Every large organization has similar behaviors. They all believe they are the smartest, best, and perfect: "The best that ever was and the best that will ever be". You can only have a master/slave relationship with them. If you are negotiating, they know you are weak. They don't admit fault, are totally out for themselves, will lie in a heart beat, are always looking for a scapegoat and come up with crazy stories to make the problem go away.

Nothing changed from then to now.