Dave - What do I make? A variety. Mostly for myself, but I have sold a few. For market I have golf-ball and beer-can caliber coehorns turned from 4140 on cnc equipment. When I get the next batch of either ready I'll advertize.
For myself I built my first - OLD beer-can caliber from a piece of hot-rolled steel back in '74-'75. Fired it on July 4, 1975 - 200th anniversary of the first shot heard round the world. Did so at Ft. Devens, MA about 20 miles down the road from the bridge between Lexington and Concord.
The second I had a local company make for me - 4.55 bore diameter, shoots 4" pvc pipe filled with concrete - 3 to 7.5 pounds goes 350 meters. Pictured on the left. Industrial hard chrome plated inside and out. Tube and trunion weigh 103 lbs.
Did a hand-held "hand gonne" in golf ball caliber - pictured in another thread here. In the middle ages (1300 or thereabouts) they were stuck on the end of a pole and would pennetrate body armour with 1" rocks.
Working on a bowling ball mortar. And thinking about doing several in smaller calibers like 20gauge (.625") 12 gauge, 1", film cannister and others.
So many toys, so little time.