922r applies only to semiautos.
Actually, the restriction only applies to certain semiauto shotguns. It does not apply to them all.
If one actually reads 922(r), you will see that in order for a shotgun to qualify for this restriction, TWO CONDITIONS from the following list have to be present on the shotgun. Just having a magazine capable of holding more than 5 rounds is not sufficient on its own.
This is what the law says:
"A semiautomatic shotgun
that has at least two of the following: a folding or telescoping stock; a pistol grip that protrudes conspicuously beneath the action of the weapon; a fixed magazine in excess of five rounds; and an ability to accept a detachable magazine."
So as long as the shotgun has no pistol style grip, does not have a folding stock, or is loaded via a detachable magazine, just adding to the capacity of the magazine tube is fine, as long as it does not go over 10 shells.
The letter that GoTigers so mistakenly referenced and posted refers specifically to a tactical shotgun with an extended pistol grip, thus making it fall under the law.
Anyway, I hope this better clears this matter up for everyone.
And I know this to be a fact and absolutely true, as I own an imported semiauto shotgun with an 8 +1 magazine capacity.
If you go to the Briley website, you will see that they are selling magazine extension kits for many foreign made semiauto shotguns.
