About the markings on the bullet. Not that it would be the best way, but wouldnt it be possible to alter the "print" of a gun by damaging the barrel. Of course you would also have to pick up the spend casings, since there are marks on them too - honestly i dont see why people would use a semi auto pistol in a hit instead of a revovler; the revolver is much less likely to jam, the person is much less likely to inadverdently screw up by pushing a wrong button on the gun, it doesnt leave any casings behind, and 5 or 6 shots would be plenty if u just want to off an unsuspectning guy.