[flinter4deer]

i had a small cannon barrel made years ago,test fired it with 1oz. of fg and a juice can full of 1/2 hexnuts..sweet!..findly have all the stuff to make a nice carriage for it now...bore is 2.25 made from 5/8" seamless steel hydraulic press casing w/welded threaded breachplug....now...is it considered a 2 or a 6 pounder in ball weight?What was the standard for ball material?(iron-lead)

[arcticap]

I'm not sure what material was originally used, but Jeff Tanner makes some interesting custom hollow ball molds for cannon projectiles.

http://www.jt-bullet-moulds.co.uk/moulds.htm

[Speedo66]

The old naval cannons shot iron balls, the designation (12 pounders, 24 pounders, etc.) being what a round ball that fit the muzzle weighed.

They had some down to 4 pounders, which might be something like yours.

They also used grapeshot and cannister, which were smaller projectiles grouped together.

[JamesKelly]

You might want to have that seamless tubing magnetic particle inspected (Magnaflux, the magnetic process not the dye check) to make sure it is indeed seamless. All seamless tube does not turn out to be. Seamless, that is.
Might that weld have been stress relieved (tempered)?