Quote Originally Posted by MattR View Post
Ok so I built a gas piston upper with an Osprey conversion on a 16" bbl and a mid length gas system, it has 60 rounds of commercial ammo cycled through it for function testing and break in. I tried my reloads in it which are new remington and winchester brass, cci primers, 26gr of Varget, and 55gr bullets not crimped just pressed in with the die. Now the commercial rounds no pierced primers, my reloads all 12 pierced the primers. Too hot one would say, but I checked the reloads in a rifle length GI system and no pierced primers and no signs of too much pressure. All tests made were with the same lower with a RR 2 stage trigger. I'm lost any ideas would be helpful. Thanks

I am not familiar enogh with reloading but STOP SHOOTING YOUR RELOADS immediatley.


Not crimping the the reloads could be key here. Like I said I dont know much about reloading but if I am not mistaken when you crimp the bullet a couple of things happen:
1-The bullet is seated a bit deeper in the case.
2-The crimp provides a bit of a taper for the "Leade" of the chamber. The leade is the unrifled portion of the chamber where the bullet is. It provides a head start for the round when fired before the bullet enters the rifling. Some people call it the "Throat" of the chamber. If the round is crowded into the rifling you will get a pressure spike.
The uncrimped neck could possibly be crowding the round a bit and spiking.

With this not happening with the other upper the converion could be suspect. Maybe not venting pressure quite as quickly as a GI system causing a pressure spike.
You get a quicker gas impulse with a 16 than you do a 20.

Have you checked the headspace? The chamber could be a smidge short.
Have you checked the firing pin protrusion? .028 minimum .036 maximum.

Let us know-I am curious what you find out as I know damn little about re-loading.