I assume this bulge is uniform all the way around?
Check the finished cartridge dimensions against SAAMI specs. I suspect you'll find that the bulge is within spec and the case is being sized small enough that seating the bullet is pushing it back out, creating the bulge. If so, it's normal and you're fine.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.