Hello All - I have a question regarding cartridge pressure limits and the guns they were designed for. I'm specifically looking at the 7.62x39, as I have a Ruger American Ranch rifle that is a really handy little gun. In researching loads for the 7.62x39, most all of them top out at around 50,000 PSI. Is it safe to try to load this round to higher pressures, say 60,000 PSI, for use ONLY in this rifle? I understand that this would be most likely catastrophic if used in an AK or SKS, but the American is a modern, strong bolt action that is chambered in other cartridges that go as high as 65,000 PSI. I know the 45/70 has many different levels based on the guns it's chambered in (trapdoor vs modern lever action), so I'm wondering if the same would apply here.
Is the weakness in the brass, or is the pressure kept lower because of the guns normally chambered for it?
Thanks
GunLoony - your question makes sense, and with some cartridges that's a reasonable thing to do. You can definitely make more velocity with higher pressure, obviously, and your rifle can obviously handle it given the other cartridges it's chambered in.
However, in 7.62x39 the weak spot is the brass. You can turn up the pressure a little bit and should see some gains over factory ammo, but won't get to full pressure capability of the rifle before you see brass damage. The internal web of this case is very short, so the brass will swell around the case head with high pressure, and if you go far enough it can look like a belted magnum. Obviously that's very bad and if you see that, back off a bunch. The same thing is true for the Grendel, since it was made from the 7.62x39 (with a couple other cartridges in between along the way).
Now if you want to be a true rifle loony - run a Grendel body reamer into that chamber to create a 7.62x39 Improved for more case capacity to go along with your higher pressure loads.
(Seriously though - this is possible, but research reloading dies for this chamber first.)
