I wanted to add a little weight and slow cycling a hair, as well as lessen felt recoil for a smoother action. I've actually tried one that was on another s12 ( I used his carrier / my bolt ) at a local gun club on a family and friends day I was invited to. With my tac 47 plug my s12 cycled fine like usual, but it felt smoother and didn't seem to slam rearward to the receiver heel as hard. It may have been all in my mind but I want mine set up that way any how. I don't need anything re-profiled or polished, just the new piston installed, vertical charging handle cut and an original type welded