ROLEXrifleman
Master
I'm with bigedp51 on this one. I get primers that look like that sometimes with loads that are well within safe operating pressure. Don't confuse cratering with flattening if primers. Ctratering occurs when the primer forms around the firing pin flattening actually pushes the firing pin back and then forms around the breech face. Much greater pressure in one over the other. Then we have the issue of unsupported chambers. Glock oem pistol barrels are notorious for leaving behind "guppie bellies" on brass. When the brass is fired it stretches one way beyond the scope of its initial forming, then it is resized back to spec and stretched another way. If the sizing die doesn't go all the way down it actually leaves a section of unsized stretched brass down there. Either way the brass is already weaker than when new. Now, fire it again from an unsupported barrel and you have the possibility of this happening. Mix in a hot load or bad loading habits and kaboom!
does your carbine have an un supported barrel? If not then it was an out of battery detonation, but that's not likely.
does your carbine have an un supported barrel? If not then it was an out of battery detonation, but that's not likely.