I recently ordered a 14" 6mm TCU Contender barrel from Dave Van Horn. When I received the barrel, it looked a little long to me. I measured it and sure enough it was 16". This is going to be a bench gun so I don't mind the extra length, but my question is this. Is this barrel too long to use as a pistol. I live in Missouri and can't find any state laws concerning this, are there federal laws that set these limits? Any help is much appreciated.