Syntax Error

I was wondering if anyone can share their experiences for handloading for the Sturmgewehr 57 rifle with its unique double shoulder chamber. From what I have gathered, the second set shoulder in the chamber is to allow the bolt and the chambered cartridge to pinch the shoulder slightly to prevent the bolt from bouncing back under full auto fire, for example. I was wondering if anyone has had any experiences for resizing for brass that has been once fired out of this particular chamber. I have read up on some experiences from the Swiss Rifle Forum about a user whose Stgw.57 blew up on him and he seems to claim that it is because of this double shoulder and the chamber fluting allowing for the brass to be stressed at a particular existing flute under fire and rupture a case, but I am somewhat skeptical of this analysis. It would seem to me that this particular owner's rifle may have either been improperly sized and allowed for an out-of-battery detonation, or his load was not a safe level, or his brass was somehow compromised previously somehow. It seems to me with a reasonable load and strong brass, with proper resizing to take account of the double shoulder, that reloading for a Stgw.57 should be possible and retain a reasonable margin of safety. I have experience for reloading for other fluted chamber firearms such as an HK-91 series of rifle, and have had no issues. I plan on using Prvi Partizan brass and annealing the cases after every firing as well.