Powder Keg: It shoots, what else, 16 lb. bowling balls!! Actually, I have some 1/2" lead balls and will probably see what it does with one of those.
Cat Whisperer: I don't have much of a selection of larger drill bits, and the next larger size above 1/2" is one that measures .580, which is what was used. That's probably a bit "loose" for a 1/2" projectile. But it was made as a novelty more than to shoot, even though, as said above it will probably be fired once with a 1/2" lead ball.
As for the trunion attachment---and all you dudes with milling machines and other such equipment---don't laugh!! The trunion is drilled and countersunk for a #10/24 flat head machine screw. The base of the mortar was drilled 3/8" deep and tapped. In other words the trunion is screwed to the mortar, with a bit of epoxy applied to the threads to, hopefully, keep the screw from loosening. But getting loose shouldn't be a problem since, for the most part, it will grace my desk as a paper weight.
