Home Forums Hunting & Shooting Ask The Gunwriters Can the experts clear up Pressure confusion?

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On another forum a gentleman describes some test that he ran on some lever guns. A Winchester 92, a Winchester 94, and a Marlin 336 were each chambered for the 454 Casull and test fired. The 92 was made for pistol cartridges and the other two, the 94 Big Bore and the 336 were made for cartridges developing 52,000 CUP pressures, the same as the Casull.

According to the author, The 336 became inoperative after some 30 rounds. It did NOT blow up but was so battered that the action would not function.

Shortly thereafter, the 94 BB suffered the same fate.

The Winchester 92 took the licking and kept on kicking...indefinitely.

His opinion; The 92 is a much stronger action because of the square locking bars that lock the bolt. The other two were destroyed because of the angled locking bars. (oversimplified)

My question; Why did the two actions fail so early if the are designed to operate at the same pressure as the Casull? ( Both guns are factory chambered for the 356 and 375 Win.)

Any of you knowledgeable ladies or gentlemen have a definitive answer?

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I might be wrong, (probably am), but my understanding is that the 94 and 336 were designed for pressures developed by the .30-30 design of cartridges--in the 30,000 to 40,000 PSI range.

They might have been proof tested for 52,000 CUP, but I don't think they were designed for this pressure as a steady diet.

52,000 CUP is a lot even in a modern bolt action. Not really a lot, because the bolt actions will withstand these pressures on a regular basis, but they are designed to operate in that range and perhaps a bit higher.

Can't answere the question about the M 92. Don't know anything about them.

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My 375 Win has handled the 50 -52,000 CUP(Hodgdon's data) pressures quite well for years. My 375 Win. in a marlin 336 is still going strong after a couple of hundred round of the same.

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I see two distinct issues here - first and foremost a confusion - often seen in hydraulic systems between line pressure and ram pressure where the ram has a significant area - that tends to assume all cartridges at the same pressure are equivalent in impact on the firearm.

Not so.

My carry gun frex is a 1911 in 9x23 and works very well thank you. Were I to load a .45 Auto case to the same peak pressure or even the same area under the curve or even the same pressure curve I would be well over the line - I do have a .460 Rowland which requires IMHO major changes and still does not permit the same peak pressure as the 9x23 permits with fewer changes (my 9x23 was smithed by a competent smith who has a certain rep for 9x23 pistols - and who stopped reaming long chambers in S&W 940 revolvers - I do not suggest Superface is never an issue in a 1911 platform)

Similarly in a rifle action - just as in the 1911 - a smaller case head can be run at higher pressures than a larger case head at least most of the time. Here there may or may not be other issues such as the much longer case gripping the chamber walls or maybe not, bottleneck versus straight wall and all the other things that might be tested for. Consider low wall and high wall and pressure for a thought experiment.

In any event it's not just a matter of equating peak pressures, be they lead, cup or psi, and calling it good.

Second issue the difference between the '92, '94 and 336.

I have no useful comments there beyond noting that a lot of different rifles have worn those labels at different times from Miroku reproductions of the '92 to the whole family of the 336 including .444 and .450 Hornady and the whole West family of cartridges and on and on. If I had doubts about the 336 family I'd look at the guns out of Alaska and figure the gun is strong for all practical and some impractical purposes.

The longer I'm around this stuff (half a century plus, now) the more I become convinced that maybe, just maybe, the guys who design and build guns know what they're doing.

If a given gun isn't chambered for a given cartridge maybe, just maybe, there's a damn good reason. Maybe, just maybe the designers actually tried chambering that gun in that round and discovered it's a bad idea.

But what do I know?

Never forget when thinking about Pressure that part of the formula is an area.

Not all cartridges have the same area.

The back thrust on the bolt face is for example: PSI TIMES the area of the cartridge base.

So the thrust of a 223 is OK in a T/C Contender, but the thrust of a 307 Winchester isn't.

The same piece of physics applies to all actions

Most actions will not fail from "backthrust". The case fails
first. It is the unsuported brass at the rear of a 45 ACP
that limits it's pressure.
Good Luck!

You must be talking about that famous with "Glock bulge", not a 1911.......

I have to agree though. If the action isn`t beaten to failure over time, case failure normally is the problem.

I'm still not an expert but I do think that I can - if somebody will pay for powder and bullets - crack a typical 1911A1 slide at the stress risers and shoot it backwards off the frame with enough high pressure loads that don't blow the brass. I know I can stretch the slide and crack it and I certainly fear I can rupture it.

As discussed by the real experts on other threads about pressure guessing there will come a time the action fails - maybe sooner maybe later.

Here's what a real expert wrote:

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� Catastrophic failures of overloaded rifles may occur with either the first over-hot round, or they may occur only after years of repeated use of over-hot loads. In the latter type of failure, the rifle has appeared "safe" with these loads, clear up until the time one round "caused" the failure "for no apparent reason."

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� The maximum safe limit for many rifles and cartridges is well below the level of peak pressures that many cases can handle without any discernible or measurable indication of excess.

And a good deal more at: http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/ubb/showflat/Number/19112/page/0/fpart/1

And again if I wanted a 336 in .45 Casull I'd talk to Jim West who mentions it in his FAQ's at Wild West Guns.

So far I no "Real Expert" has spoken with intellegence on
metal fatigue/ pressure.
The 1911 does have unsuported brass sticking out of the
chamber.
Good Luck!

Read ye all and know that this is true wisdom.

You can run most any mechanical device - rifle, car engine, or can opener - beyond it's design specs once, or twice, or even twice times 100 without seeing anything wrong. But keep doing it and someday something's gonna blow. If your can opener explodes you've just got tomato soup to clean up. When your rifle blows, well, that ain't tomato soup on the bench.

From a cost/benefit view, there is really no justification for pushing a rifle, espeically when bigger rifles are readily available. The most benefit you get is a few more fps, a few more grains of bullet, and you're betting that you don't pay the cost with your face or other body parts with every shot.

But the results of the eventual failures do make for some cool pictures.

Amen and amen again, Jim. That was said as well as what you quoted.

On another website, I have a recurring debate about that very thing. He clings to load data from the 1970s -specifically from Speer #8- because he says its always been safe in his guns despite being way over load levels recommended today. I always end the debate by saying his "hasn't blown up yet" argument always ends with that "yet."

Wasn't that the manual built upon pressure data figured from bad tarage tables for the copper crusher slugs?