I think the legal limit is 18.5 inches, and there is also a limit on over all gun length. I don't know what it is though.

You could probably get away with using a cut off barrel for home defense, but I think a tighter choke would work better. Not to mention it would render the gun useless for anything else. At least if it had a choke you could shoot trap or hunt with it if you really wanted to. Of course it sounds like you already have a barrel for that though.

Here is a link to the post were I did the test with different chokes and shot.

Shot Test Link bottom of the page last post

Basically I shot some 7.5 shot with a I/C choke and it peppered the board at 10 yards. I shot the same load at 5 yards with a full choke and it went thru two pieces of 3/4 inch MDF. And with a super full choke out of a 28 inch barreled pump gun with #6 shot it went thru both boards again at 10 yards. So I think the tighter the choke the better penitration capabilities smaller shot has at closer distances. Basically using a turkey choke for home defense would let you get away with twice the distance as an open choke with the same load.

I don't know what would happen with buckshot, I have never used it and don't really intend on buying any just to play with. Goose loads would probably VERY well though.

Just my opinions any way.

Paul