Guys I have a 7mm PRC with a 22” barrel. We made up some Barnes LRX 168 gun loved them was getting great groups shoot around 3100fps put the suppressor on had very heavy bolt lift after that to the point couldn’t almost get open. Had to back powder off from 68.4 grains to 63 grains. Anyone ever have an issue like this?
Oh the joys of load development! How is the gun working for you overall? Are you liking 7 prc?
I’m not surprised that you saw pressure signs. That’s pretty far above what a load manual would recommend, I believe. My guess is that a safe max velocity with that bullet in a 7 prc would be around 2850fps in a 22” barrel.
Barnes doesn’t have load data for the 7 prc yet, but Hornady advertises 3000 fps with their cx bullet. Thats more like 2950 because… marketing. Then you consider your barrel is 2” shorter, so now we’re at 2900. Then your bullet is heavier so 2850. Also, I believe the LRX has a longer bearing surface than the CX, so that ups pressure too. That’s what I’m basing my 2850 guess on, at least.
It’s pretty normal to not see any pressure signs on the brass or heavy bolt lift until you’re 10,000 psi above the max pressure of the cartridge. I’ve seen it happen a few times where there were zero signs and then I add a tenth grain more powder, and the result is an OBVIOUS and dangerous over pressure sign like you saw.
Since the LRX has a long bearing surface, it increases pressure a decent amount over a lead bullet. Adding a suppressor can also add some pressure due to the back pressure. Some of them are worse than others about it.
What powder are you using?
I’m really liking the 7 PRC. It shoot about 5/8” group with the suppressor and 1/4” with out it. I’m using the H1000 powder. My current suppressor is dead air sandman and I’m waiting for approval from the atf for my other which is the nomad ti do you think it will change the pressures again when I go to the TI?
If you’re down in the safe range of the cartridge, I doubt you’d see much difference switching between suppressors in terms of pressure.