http://www.centerfiresystems.com/SAI-12IZ-107.aspx
All the saiga barrels come with thread protectors. The Polychoke just screws on in their place. Also available are several factory chokes that also screw on the barrels. I don't use mine or any other shotgun for large game so no real input on their use for this. I do know that this past year I had to work on three of my buddies Bennellis in the field and never once on my saiga. Yes box magazines are a pain if you are not able to figure out how to change them quickly. I carry a belly pack with two pockets which holds five mags just fine in the larger one and spare shells in the other. With 10 shells loaded, when hunting duck or 25 shells loaded hunting other game, I don't see a need for more rounds. The number of rounds carried loaded in the mags is almost double the bag limit.