I have been toying around with making small mortars for a little while. This is a challenge for me, because I don't have the proper tools to do it. I have no lathe or mill of any kind. All I have is a Harbor Frieght drill press with only a 3" plunge depth, a 48x6 belt/9" disk sander, 8" grinder/buffer, welder, Dremel, and hand tools. (Edit: Oops, forgot the table saw.) For that reason I can not attempt any conventional cannon configuration, and have to keep the mortars small.
I normally use all-stainless and polish it as a novelty, since I can not turn any sort of rings into the barrels. They are normally just plain mill-finish cylinders, sanded progressively and then buffed. I have made as small as .177 cal out of 5/8" round. Until now the biggest has been 3/4" bore out of 2.25" round (like I made for carmy53). I don't do reduced chambers in them, to keep them strong. They are, more or less, short cannons abiding by the 3x rule, only shaped like mortars.
I just finished this one, which is the biggest I have done. The barrel is made from 3” diameter 430 stainless steel round. I bored it 15/16", which really stressed out my drill press. It was actually initially a thunder mug, but then I welded a 3/4" trunnion on it. I did not like the way my welds looked, plus I wanted it to NOT look simply like a plain cylinder with a welded-on trunnion, so I covered the welds with filler to disguise it. Needless to say I needed to paint it then. So it is painted stainless. (At least the bore looks shiny!) The bed is made of African Anigre.
I am pleased with it, so I thought I'd share this one online. I am sending it off to a buddy out of state who doesn't know it is coming. Hope he likes it.