Checked on 10ga and 12ga NEF Ultra Slug guns. Barrels are large diameter, but not alloy. I think use barrel breech section for a monoblock and put in long heavy 12ga alloy barrel, and treat the monoblock to higher strength. Use a weighted thumbhole buttstock and with heavy barrel get weight up to 16-20 lbs. Being break action and large cartridge, barrel should be 32+ inches.Ed
