This last week I've been working up some loads for a new AR build, having just dumped my range brass out on the mat to sort I realized I've been getting a few primers punched through. I would appreciate your thoughts on resolving the issue. The nickel plated ones are all Federal 205m, loaded with 55gr bullet over either 23gr of H322 or 26.2gr of BLC-2 for velocities of 2630 and 2730 respectively. No signs of excessive pressures, plenty of room to ramp these up but for the primers. The cases primed with the old copper plated R71/2 were thrown in for comparison, they were loaded with 26.7gr of W748 at 2890 fps for comparison. I know Federals are softer but never had the issue with my Ranch Rifle, I'm sure you can see the ejector dents from previous firings from that gun tossing deadly projectiles to the right.
Not every barrel is the same, not every chamber is the same, and not every primer is the same. Loads developed in my Wilson barrel, NM AR15's, blew primers in my Krieger barreled Space gun AR15. Wilson barrels are button rifled, Krieger are cut rifling, and Krieger barrels are tight regardless of their caliber. And, when Winchester went from the nickle (Customer service said zinc) plated primer to the brass WSR, (about 1999) loads that never bothered the nickle WSR pierced the brass finish WSR and ate up firing pins. Winchester said they made the primer more sensitive by making the cup thinner. That is bad, bad, bad, for service rifles.
Do what every AR15 service rifle eventually learns: cut your loads by a 1/2 grain till you stop having pierced and blown primers. My Krieger barrel loads were at least 1.5 grain less than my Wilson barrel loads, and I had to cut the brass WSR even more. Eventually I shot up all the brass WSR and went back to my old loads with the great and wonderful CC#41 primer, which is the only appropriate primer in the AR15. It is made to the military sensitivity specs. I had an in battery slamfire with the brass WSR, on first relay, my scorer on second relay, his AR15 slamfired also in the standing stage with Federal match primers. Slamfires are rare, but having your gun go bang when you did not want to makes a big impression to the guy behind the muzzle. A friend of mine, at Camp Perry, could have been seriously shot on the firing line by a Junior. It was during the standing slow fire stage. He said the junior on his relay was handling his rifle dangerously. I think it is possible the kid was holding his AR in line with the firing line when he was loading the thing. I have seen that by another shooter, the guy raised his rifle up to his face, put a round in the chamber, and chambered the round with the rifle parallel to the firing line. I think that was insanely dangerous to his face, and if the rifle discharged, anyone down range of his muzzle. I think that is what happened with the Junior, or at least, the muzzle was not pointing downrange. The kid's rifle slamfired and the bullet passed between Bud's left arm, extended holding his rifle, and his body. Just a little more weaving and the kid would shot him through the body.
I used to get into arguments all the time with trolls who absolutely insisted rifles did not slamfire due to primer sensitive. Thank goodness for the internet, I could bury the troll in posted accounts, not that it really changed the position of the troll. Some trolls are just out to kick the ant heap over and watch the ants scurry. These master manipulators are out there, and they have fun messing with the ants.