Deformed shells

The fired shells probably won’t chamber until they’re run back through a sizing die.

Are these reloads? Looks like the “swelling” occurs at about the seating depth of a wadcutter. Probably nothing to worry about if the gun’s running fine.

If it's a bulge, I would guess you have a bad chamber (pit in the side of the chamber). Kind of makes me wonder how it got extracted. Use a straightedge to check the chamber walls?

Looks like perhaps you are using a full length wadcutter expander with cases that are tapered on the inside. (not enough depth in the case for wadcutters) The case wall gets thicker toward the primer end of cases. Some cases start to taper higher up than others, and that creates the issue you are having.

"Wobbley" had a list of cases that were suitable for wadcutters.

If you have any Federal or Winchester casas, try them and see if the iddue goes away.

JRV wrote:The fired shells probably won’t chamber until they’re run back through a sizing die.

Are these reloads?  Looks like the “swelling” occurs at about the seating depth of a wadcutter.  Probably nothing to worry about if the gun’s running fine.  

No they ar not reloads...made in Germany by Geco

Oversize chamber, or at least on the high end of the tolerance. Assuming you're trying fired cases from the 52 in the revolver, its chambers are tighter.

Sizing them for reloading fixes that. Assuming you're reloading them ...

Sizing ... 38 Super die is a bit bigger, reduces the amount of abuse to the brass for lead bullets.

My M52-2 and M14-3 bulges the brass also, but nearer to the case head. I use a Lee carbide 38 Super sizing die to smooth it out. I think when I was shopping the Lee would get the closest to the case head in my Hornady L-N-L progressive press.

I found S&W chambers were larger than Colt revolver chambers so ironing out the bulge was the only way to load ammo that would fit all three chambers.