I am a new owner and am on a learning curve so please forgive my question if it is a no-brainier! My S12 has the Pistol Grip mod and does not have a bolt lock installed. It has the slot in it but no lock mechanism. When I asked the shop owner that sold me my S12 he stated you lose that option when modified, and no one makes a lock to fit after the PG modification. Fact or Fiction? If fiction were can I get the parts to rectify the lack of a bolt lock?