The 1911 Under Pressure

[Candiru]

Not sure to put this one, as it's a general theory type question not so much related to a particular conversion as the general practice of making the 1911 platform shoot other calibers that don't start with ".45" and end with "ACP".

Thing is, most of these other calibers, from .38 Super to 9mm to .40 S&W to 10mm, all the way on up to .460 Rowland and 9x23 Winchester, operate at much higher pressures than .45 ACP, some by a huge margin. (.460 Rowland operates at around 40K CUP, and 9x23 Winchester hits a ridiculous-for-handguns 50K CUP.)

From what I've gathered lurking on this forum, higher pressures don't always get along too well with the 1911 due to the fact that most factory barrel/slide fits don't involve engagement with all three locking lugs. I recall a few threads wherein Tuner expressed some trepidation at shooting 460 Rowland in any gun where the barrel hadn't been fitted to the slide. Then again, I've never read any reports of .38 Super guns shooting themselves out any sooner than their .45 ACP equivalents, and the Hi-Power seems to do pretty well with a similar lockup system at 9mm pressures.

So this is my question: Is there any sort of rule of thumb when it comes to bullet weights and pressures as to what is "healthy" for the 1911 platform and what constitutes trying to push it too hard? Is cartridge pressure the only consideration, or does the bullet weight play a part?

[Hunter]

It is my understanding that bullet weight will directly affect pressure. Two same powder charges under different bullet weights will generate different pressures (the heaver bullet will have more pressure in the chamber due to a greater pressure needed to move a heavier mass). A good reference for the max pressure you would want to generate in your 1911 would be a good loading manual. A few of my loading references list loads with CUP. If you find a max charge with a certain load the CUP listed is as high as I would feel safe going to in a 1911 in good working order. I am not a ballistic expert so I am sure you will get better answers on this.

[horse 91-A1]

I'm in the process of researching the 9x23 that had its origins about 100 years ago as the 9mm Mauser. It runs at rifle pressures, about 46,000psi; but the casing is also thick enough to be used in an unsupported chamber. Another requirement is its requirement to use small rifle primers to reliably hold up under the pressure.

From what I've read, the 9x23 recoils less than the .45auto in a 1911 while running .357mag ballistics. It's COAL and slight case taper may make its feeding more reliable than .45auto.

The 9x23 has picqued my interest as it can match hot .357mag loads and do so in a semi auto format such as 1911 and Glock 20/29.

Bob

[pa_guns]

Hi

Obviously this is overly simple.

Pressure is rated in pounds per square inch. That's not the whole story though.

The force back on the breech is going to be the PSI times the area of the case head. A smaller case head will put less pressure on the breech than a larger one with both at the same pressure. A .45ACP has a lot more case head area than a 9mm for instance.

The place that most pressure problems show up on a 1911 is in the part of the brass that is unsupported by the chamber. If you look at your barrel with a case in it you can see the part of the case near the ramp that is not up against any steel. The design of the brass and the design of the ramp both impact how many PSI you can stand in this area.

Assuming you don't blow out the case, the pressure on the breech is transferred to the lugs that hold the barrel to the slide. The more lugs that mate and the deeper they mate the better.

Your worst case is a cartridge that both has a larger head *and* runs at higher pressure. If it also has brass that is "skinny" near the base you are headed in another wrong direction all at the same time ....

Don't know if that helps or not ...

Bob

[1911Tuner]

Assuming minimal headspace, the problem comes at us through the lugs...and yes...the .38 Super and even the 9mm pistols are hard on lugs that don't have good vertical and equalized horizontal engagement. back in the "day" we used to refer to the .451 Detonics as "Lug Busters" because that's what most of'em did. The owners who popped for the bucks to have a barrel correctly fitted fared much better than the ones who bought into the drop-in theory and threw caution to the wind, and some are still buying into it with the .45 Super data, and no reasoned, logical, or factual argument will sway these mindsets...but I digress.

Study the locking lugs...barrel and slide. They're not half-moons. They're crescents. Little slivers that aren't much more than 1/8th inch thick and .050-inch tall, save the first lug wall, which doesn't have a slot behind it....and that height is ONLY if you have full vertical engagement. Most factory barrels don't. If you're lucky, that will be the one that bears the brunt, and the 40,000+psi ammo will take a little longer to beat it out so far that headspace becomes a real issue...and THEN case head support is the problem.

If you're not so lucky, and get one of the factory barrels that place the
load on the second lug only...or worse, on the third one...it won't take long
to realize the error of your ways. Some of the guns that underwent the .451 conversion sheared a lug within 100 rounds...which caused an immediate transfer of the locking chores to the next one in line...which opened the breech by the distance required to reach that lug...which usually caused bulged cases because of the extra amount of unsupported case head.

One gun blew all to Helen Gone. I mean, a catastrophic, slide peelin', barrel blowin', Honest-to-God kaboom...complete with bloody fingers and face. Instead of the lug simply shearing, it cracked...and it cracked below the junction of lug and barrel...and when it let go, it actually pulled a piece of the barrel out with it clear into the chamber, complete with a bloody face. Only the high-quality shooting glasses saved his eyes, and it required a trip to the ER to remove the shards of hot steel that imbedded into his skull.

Boys and girls...Any pressure that can drive a 230-grain bullet to 1200 fps in just over 4 inches of rifling is more than enough to blow your jawbone loose from your face. If you want a .44 magnum...buy a .44 magnum. The gun was designed around 20,000 psi....not 40,000. Would you load up ammo that hit 110,000 psi and shoot it in your Mauser or Winchester M-70?

[horse 91-A1]

Thanks for taking the time to write all the info, I know lug line up is critical and outside my working knowledge. I read at one time the 10mm (runs slightly higher pressure than .357/.44mag) stretched the 1911 limit a bit. From what I've gathered on the "omniscient" web, Colt may or may not have had a kit for the 9x23 during the 90s with their .38 Super models. :)

Bring it up to the present and Bar-Sto makes 9x23 barrels for the G20/29; which are already high pressure 10mm frames. Winchester ammo loads the 9x23 at the same MV as the .357mag and about 100fps more than the .357SIG. Oregon Trail ball parks their 122 laser cast handloads at nearly 1500fps in 9x23 from a 5" barrel.

Have the G20 and 9mm dies, just need to know what other mods are needed, barrel plus brass and experiment time. :D

Bob

[1911Tuner]

I figgered ya understood it, horse. That post was more for the benefit of those who have their minds made up and won't be swayed from their beliefs.
like the 400+ pound Black bear that was killed in California...of all places. Everybody knows that Black bears don't get anywhere near that big...not even in the high country. ;)

[Candiru]

That makes a lot of sense. I've always wondered about the fact that .38 Super is considered almost a canonical caliber for the 1911, even though it operates at similar pressures to .45 Super, which is clearly a bad idea. I guess logic and reason turned out to have been right all long--who'dathunk?