Got the tank for the BB Mortar and the metal needed, The trunnion will be welded on the rear of the powder chamber, 2 in. rd. by 12 in. long. I need help with the sled now, I can get oak, red elm or pine in any lenght and size. Would like to make something that lays flat, take the barrel off and not weight over 80-100 lbs. also that will take the recoil, any ideas for plans for a strong one, Thanks- Joe