“does anyone know what the laws are for ‘mkodifying’ your shotgun”
Minimum barrel length is 18 inches or else you have to get a class 3 license for a short barreled weapon. Under 18 inches you are in violation of Federal law.
And overall length has to be 26 inches or more. I know this law makes absolutely no sense now that the Supreme Court has ruled that the Second Amendment affirms a right to a loaded pistol in common use to defend yourself. It only made sense if it were the precursor of registering and highly regulating pistols in anticipation of banning them.
Now that pistols have been taken off the "ban" table by the Supreme Court, the prohibition on short barreled rifles and shotguns is nonsensical.
It will take a politician with foresight and courage to remove this archaic absurdity of "progressive" assaults on the Constitution, but the case is straightforward and would be rewarded with immense support.