Blaster mentioned in a note to me that there are some things that I should mention so here goes.
The tube is indeed seamless and was marked as "High stress" original use was for heavy equipment pivot bushings, machined tough even w/carbide point tool for thread cutting in the breech. I will Rockwell test it tomorrow to see how hard it is.
The bore size is just a few thou over three inches the wall thickness is a few thou over one inch and very uniform all the way around.
The projectile is a standard (Oz? will check) vegie can filled w/quickcrete I never did weigh one, will do that on Thursday as well. The windage is a little lose slip fit , will slide freely in and fall out if the barrel is pointed down a little. Had a big ball bearing from a oil drilling rig rotary table that fit about the same that I would like to try.
Powder charge was five level tablespoons of Cannon Grade BP. Also fired with four level tablespoons of FG BP.
When I get photos done this gun and carriage will probably look a little untraditional with the auto axil and wheels and the way over size trunnion band. In answer to the question of the trunnion band it is 5" ID, 7.5" OD, 2.5" in length REALLY tough stuff that turned a beautiful blue chip while machining and boring for the trunnions. I (at my son's request) drilled and tapped two holes in the top of the trunnion band to mount a long eye relief scope I have for my 44 mag. Totally worthless you might say, but, he wanted it and it really is fun to try to zero :wink:
This is the coolest group to read and there is such a wealth of experience shared. I am as well , one very concerned w/safety, my day job is working on an ALS ambulance for ten 24 hr shifts a month to support my addiction to making Damascus steel and knives and now cannons :lol: In my day job I see enough to make me VERY cautious .
Thanks for your help folks.