Glad you’re enjoying the FX9. I run a 16” carbine in AZ for PCC.
Mine isn’t too picky about the lock back, working with MagPul and ETS mags, not so much with actual Glock mags. I haven’t seen the case bulge you’ve got. I’m running a KeenShot hydraulic, AR10 spring, and short stroke spacer to let the bolt go back just far enough to engage the BHO.
So far it’s been a good combo, got most of one season on it, mostly level 1club matches.
RTL