Brass Catchers seem to be swallowing up casings - they don’t appear in the inventory or when you remove the magazine and/or brass catcher. Tested on a few rifles and the Mossberg 500, and seems to be universal.
True. Playing 5864, same deal. I think I saw it earlier than that too.
same at 
brass catcher is BUGGY.
and what i did to verify this fact:
i use COP .38 - .38 derringer revolver.
it MAY use brass catcher but i not use it. and… brass - where? there no brass. no brass on the floor…
ok. maybe when reload of derringers casings is picked out at once and automatically put into inventory. and no brass in my inventory!!!
i then try true revolver - i get enforcer true revolver .45. fire! reload! - and - the same: no casing!
so - i use true pistol. without brass catcher casings is on the floor near me. ok. get it.
with brass catchers pistol - brass vanishes.
well i go try rifles… one minute please…
get Cx4 Storm rifle with catcher installed. fire - no casing.
uninstall catcher - fire - casing on the floor. good.
about revolvers at all - what if game engine think what revolvers have internal catcher which is a bug?
Yeah, just tried using a S&W 610 and it’s also swallowing spent casings up as well.
 - same as old  rifle with brasscatcher gulps my brass
Issue still on 5938 (and a bunch of earlier builds, didn’t notice till now).
Tried with Cx4 Storm, Glock 22, Glock 19 and Beretta M9.
Has to be the code for how to handle ejecting casings. There’s checks for the RELOAD_EJECT flag and an installed brass catcher, and normal ejected rounds spawn properly.
Could well be fucked up due to their changing casings from ammo to generic for no good reason.