Well I almost got myself into trouble!

[Sixshot6]

The Ammendment Act stipulates the combination of barrel and OAL only for pump and semi shotguns, whether S1 or 2. All other S1 shotguns only have to conform to 12/24.

Likewise, S2 only stipulate barrel length in this regards and not OAL. You could have a SxS 12ga with 24.1" barrels and a pistol grip only.

There were a load of single barrel .410 folding shotguns knocking around ages ago that had a pistol grip only with a 24" barrel and were sold as "Ratters" on s2.

Funny story, I had an argument with a dealer once over uk shotgun barrel length, he said all shotguns had to be 24 inches, I said it was only pumps and semis and everything either conformed to 12/24 on an fac or the weird thing about section 2 shotties that I didn't know. He wouldn't hear, later got into trouble (though he talked his way out of it and lived to deal another day) for having a rifled semi auto shotgun barrel.

[Dellboy]

No, because it needs a 24" barrel for s2 and the Marlin .410 is 22". The Winchester 9410 is available as a s2, if you can find one.

So a barrel extension and a restricted mag then ?