True the reciever was made for a muzzleloader application to begin with. Had the reciever been made for a cartridge and converted to a muzzleloader you are getting to the NFA question. The NFA rules are not logical in any way. For instance the SBR ruling. This was put in by some senator who said Americans did not need shoulder stocks on handguns. In 1934 the country was very antieuro. The senator said Americans did not want this stupid Euro trend. There was no crime issue. Thanks to this you can not stock your vintage P-35 Inglass made for a stock without a cost of $500.