I don't have one of those barrels, but it is my understanding that it is basically a direct- replacement, screw-in barrel. The breech is probably screwed into the butt-end of the barrel like a modern inline and the stock firing pin sets off a 209 primer that is installed in the breech for each shot. I am unsure what the twist rate on the barrel is, but I would be willing to bet it is probably 1:28" (or soething real lose to that).

This barrel is only for the 12ga model 500...20ga owners like me just have to suck it up and buy a regular M'loader.

"Every moving thing that liveth, I give unto you as meat" (Gen 9:3)

Trust God..........but keep your powder dry!