I have two SIG OEM 6 rnd'rs .
The slide rarely ever locks back with one mag and only 2/3rds of the time with the other
Doesn't matter what ammo...light or hot, ball or HP.
so maybe it's common???
Mine flings the brass pretty consistently .
To the right and forward between 2 and 3 O'clock .
Distance depends on the ammo's octane rating ...
Is this the first time you've shot yours,
??
..L.T.A.