Hey Everyone,
Just posting about the time I played around with some home-loaded 9mm sub gun ammo.
I used an AR-9 that I built with a 8.5in barrel, 10.5 OZ buffer, a heavy 308 trigger kit, and a 338 Lapua recoil spring. The recoil spring makes it super stiff in a straight blow back with about 15-20 pounds to charge the gun.
Now on to the fun stuff. Yes, I know it's pretty risky to push 9mm this hot (and probably pretty stupid), but I did a standard 9mm case with a Winchester small rifle primer, 7.5 grains of AA7 powder with a 147 grain FMJ on top, and COAL was 1.150 in. According to Quick Load it should go about 1300 FPS and be about 46K PSI. Please note that if the gun is not completely in battery you WILL have a case blow out on you. I also talked to a few buddies about the AR platform and they said that the platform itself should be able to take standard 556 psi if you can keep the bolt closed long enough.
It is super fun to shoot. It sounds like you are shooting hot 115 grain loads and because of the heavy recoil spring and platform there is not a lot of recoil but it is sharp. It has no problem pushing that recoil spring and the 10.5OZ buffer back.
I hope this helps anyone looking to load 9mm super hot and please be careful when working up way above max PSI for any caliber.
Thank you all,
Alelord