Stupid law. Doesn't take into consideration 1) revolvers or other non-semi-auto guns; 2) replacement firing pins; or 3) Brass-catching devices for starters.
It would be easier for a criminal to figure out a way to use this law to his advantage in "getting off" because the evidence can't match up the shell to the gun he got caught with. "IF IT DON'T FIT YOU MUST ACQUIT".