Did the bullet clear the barrel?
If the case did not rupture, there was not a lot of pressure. So either it was an early unlock or if significantly out of battery, then there was not a lot of pressure generated.
Yes, I both felt "near normal" recoil, plus I opened it up to look for obstruction. I am currently feeling like it was an early unlock that caused the bulge.
You said there was a double fire. Soft primers will increase the risk of a slam fire, but you still need the firing pin to stick out, either because its dirty or because of hammer follow (hammer follow because something is wrong with the disconnect or FCG), or some issue with the firing pin/BCG itself.
I inspected the trigger group last night and all looks good as far as springs and such. I also repeated the disconnector test about 50 times and it never let go when returning the trigger forward after it grabbing the hammer back.
Firing pin did have some carbon build up on the face that hits the bolt on the inside. I cleaned that and it seems to not stick so much. In my early 223 reloading, I had not done so great of a job swaging pockets. I once and a while had deformations of the primers when forcing it in. I may not have been so diligent in tossing rejects like I am now.
I feel strongly until ruling things out (which may never happen) that 2 things are at play. Sensitive/deformed/faulty primer and something wrong with the gun. It could be just one of the two and a 1 in a 10,000 instance. who knows
Most everyone who spends time with an AR knows how when you load a round, the primer gets a little tap/divot on it. Nearly all ARs will tap the primer with the firing pin when loading a new round.
I started late last night pulling loaded cartridges off my stripper clips to visually inspect. I have a number of loads for 223, Cheap armscore plinkers, Xtreme bullet fmj plinkers, Nosler varminter (more accurate) and 69gr SMK.
I have some boxes I reloaded over 4 years ago that were tucked into the ammo cabinet, In an effort to try to shoot the old stuff first from plinking guns, I had moved those into and onto the top of the ammo cans sorted by loads.
The "undisclosed" number I will inspect will keep me busy as I do it in small chunks.
I also have more that I prepped and primed during the beginning of Covid while listening to Zoom meetings for work. I'm going to inspect those too.