Points to Ponder
A few things to bear in mind whenever dealing with a 1911-pattern pistol
in any caliber other than .45 ACP...especially the 10mms.
The working pressure curve of the 10 is outside the parameters of the design. The 10mm pistols were massaged, tweaked, and slightly reengineered in order to accept it. This pressure curve/timing issue
with the Big Ten is pretty close to the limits, if used in full-power loadings.
Velocities attainable with the 10 require powders with a slower burn rate
than the gun was designed around, and allowances had to be made.
This also holds true for many of the plus P loadings in .45 ACP caliber...
which may explain why some 1911s will run fine with such ammo, and other choke on it. I believe that it's at least closely related.
Whenever slow powders are used, the pressure curves hold their peak for a longer period, and if things are just a little out of whack, it puts extra stresses on the extractor...which was designed to pull a case at nearly zero pressure and expansion in the chamber. With the pressures and curves of the .45 ACP round in a correctly timed gun, the extractor is doing very little extracting against resistance...Some 1911s will function surprisingly well with no extractor at all. When the slower powders of the
10mm are in use, all that goes out the window, and the extractor is working harder to extract the fired case. If the unlock timing on the gun is
delayed for as long as possible, these stresses are minimized, but are still higher than with the original cartridge. If the unlock timing is middle-of-the-road in a 10mm pistol, you can almost bet that extractor problems will show up sooner rather than later. This would...IMHO...suggest that 1911-based pistols in 10mm caliber should be carefully hand fitted so as to delay unlock and linkdown timing in order to allow the case enough time to "shrink" down enough to provide as little resistance to extraction as possible. Only by happy coincidence do we get the optimum timing with a production pistol. The pressure curve of the .45 cartridge allows for a little wiggle room
on the timing of the gun without adverse effects. The 10mm doesn't, unless it's loaded with powder burn rates that are compatible with the design. That usually means giving up some of the velocity and energy that
the 10 is noted for, which sorta defeats the purpose for opting for the 10.
I've always suspected that this was at least part of the reason for the
downloading of the cartridge from its original velocity and energy levels.
Not so much because it was hard to handle...and hard on the guns..but to make the 1911s more reliable with the round. Design a gun from the ground up with the 10mm in mind, and it'll likely do a lot better at full-power levels.
Regard it in the same context as the M-14/M-1 Garand...You can use slow powders to make higher velocity levels, but the rifles either won't function, or they won't function for long before something lets go. The powder burn rates and pressure curves in those rifles has to fall within certain paramemters in order for them to function correctly. In other words...the
ammo must be compatible with the design.
Here endeth the lesson...
Luck!
