I just throw out any 40 S&W cases I find (at any step along the way) that exhibit any bulge or visible or tactile imperfection...

Actually, I do this with all cases for all calibers as an S.O.P. (SOP?).

This can happen while depriming, after cleaning with SS pins, while resizing and/or expanding, when hand priming or in the powder/seating step. If one makes it to crimping and final inspection (usually a case gauge) I'm going to set it apart and break it down anyway.

Cheers!

P.S. I have found less than a couple dozen bulged 40 S&W cases in years of reloading this caliber, even going way back to the "GLOCK smile" era. Over supplied with brass for all the calibers I reload. I'm easily picky.