You can get or have made a set of skeeter/chamber-mate type inserts made to shoot 12 shells in your 10. There are no full legnth tubes, they would be very thin. A 12 wad will make a very good seal in a 10 bore. Like one of the modern backbored guns that are the rage with trap shooters. Some will just take a 10 gauge brass shell and make their own on a small metal lathe.