waffle
kiwifarms.net
- Joined
- Jun 6, 2013
Carpenter 158 was good enough for TWO IRAQ WARS!
Honestly, you don't even need a better material. Rounded bolt lugs would do the trick. The deal with bolt breakages isn't the linear bolt thrust, it's the overpressure causing early unlocking and creating a torsional load. The relatively sharp radius at the root of the lugs acts as a stress riser and bolt life is reduced. I heard the M855A1 pressure issues were fixed, which lead me to an arfcom thread where Buffman said what I already knew but wasn't sure: velocities on M855A1 seem to have been dialed back. But interestingly, someone mentioned that the Small Arms Solutions/Black Hills testing of M855A1 had it conditioned at 125ºF. They did environmental testing on M855A1 by heating it up, and it's within spec. That's weird.
They don't want to use tungsten. Making billions of standard issue bullets with tungsten cores would take it away from where it's needed. That's why the 6.8 was designed around a steel core and it's blasting off at full rifle power. They need that performance to lob an ash tray of a steel core that makes up for the fact that it's not tungsten.
I really don't think the two piece cartridge (or three piece in this case) is that much of an issue. Most solid materials have a Poisson ratio of 0.2-0.2 which means that axial strain results in transverse strain, equivalent to 20-30% of said axial strain. In plain English, if you compress a material like aluminum or steel to the point of deformation, it actually bulges sideways. With the high pressures, it's possible that the washer in the case head further locks the case wall.
I could see how the pressure would force them together during firing, my main source of concern was balloon head 45 colt cases, but I can see how the geometry is different. I'm not sure that any of that will keep them together under extraction though.
I have a real good friend that works at lake city, I'll ask him if he remembers the load in a1 being decreased. I think what they actually did was change powders to one thst was supposed to be more consistent, but I'm not sure. I do know that stuff is a constant pain in the ass for them to load and only the marines shoot much of it.