Doc Av - I don’t understand why the case needs that big bulge in it to properly headspace in a .45 ACP chamber. I have about 25 .45 movie blanks, all different for one thing or another, and none of them show a bulge like this at all.
It looks to me like the round may have been chambered once and not fired, simply manually ejected, and that the crush of the slide/bolt going forward pushed back and bulged the top of the “case” (quotes use to indicate I am not counting the smaller diameter of the rose crimp as part of the “case” even though it is all one piece). Either that, or something went wrong in the process of forming the nose crimp. Of course, unless we found a full box of these to see if they all had the bulge, or just this one, I don’t see anyway to tell the “why” of the bulge. It certainly is NOT typical of .45 Auto-caliber blanks made from 7.62 x 51 or 7.62 x 63 mm rifle cartridge cases.
Of course, I realize that it could not have been chambered in an SMG type firing from an open bolt, or it would be a fired case, or a dud with a firing pin impression in the primer cup.