What do you mean bulged? Sticking out farther after they've been fired? or after you reload?
Glocks are easy to tell if they fired a round. When a round goes off in a Glock, for a brief instant the pressure sends the case shooting back and slamming into the breech face. Since glocks have a rectangular hole, there will be a rectangular box around the firing pin strike.
The primer bulging out a bit might be from when the brass is initially shot, in those micro seconds it goes backwards, and the soft metal gets pushed back into the firing pin/striker channel, taking the shape of that.
If that's round, or a halo around the firing pin hit, it's not from Glock.
Unless smiths are swaging that chamber now...
By that I mean fat at bottom of case and wont drop into barrel. Thought that was "bulged"