Edited.
I wish I had some of the ammo to pull down and see what's inside. Seeing that the Gun remained locked after the shot was probably what prevented the damage from occurring to the magazine. The primer bleeding into the firing pin hole might have played a part of the lockup by not letting the barrel to drop out of the slide.
Not sure it is a different opinion about chamber support. The delta has the least support of any currently produced 10mm. Underwood and swamp fox thought it was too little for their ammo. Buffalo bore does not.
But buffalo bore is consistently slower than Underwood is for the same weight bullet.