I have the exact gun with the the Jones underlever. I think my serial number is in the same range as yours. I had custom inserts made so I could shoot 10 and 12 gauge loads thru for skeet and sporting clays. Every once in a while I slip in a 8 ga shell with black powder to wake everybody up!
Hulls are expensive but I have quite a few. A 12 gauge insert would seem useful from a reloading standpoint. The 10 not so much. With other large guns such as the 10's which I have quite a few of, I simply recycle older reload hulls and cut them to 2" or so and load really light loads in the 12 or 20 gauge range. These work well and last forever with a glued in overshot wad.
