Originally Posted by ColoCG
Ok, your confusing me now! Which isn't hard, is it pimple or dimple and is that anything like bulge?
I always thought of the bulge as a large ring entirely around the case. The entire chamber is too large.
OTOH, the pimple (or dimple or whatever) is a section of brass that is bulged out right where it meets the feedramp. There are plenty of example photos of brass failure in this region. The entire head doesn't separate, just a blown out area where the feedramp is overcut.
I realize this is kind of an old problem and it's been known for years and years. But it's strictly a .40 S&W Glock problem that, AFAIK, has since been corrected. Still, there are probably barrels around from the earlier versions.
I don't load .40 but if I ever do, it will be for a Sig 229.