Soda can mortar diameter?

[bronzecannon]

I have seen soda can mortars offered for sale in bore sizes ranging from 2.69 in. to 2.75 in.

Therefore, I am soliciting any and all opinions on what is the preferred bore diameter for a soda can mortar and why?

Also, any opinions regarding what grade of black powder to use in a 1 inch powder chamber (soda can mortar), F or FF?
 
Your opinion(s) will be utilized in determining a possible future purchase.

Thanks

[Double D]

In the reference section of this forum we have a common item dimensions section.  Here's what  it says.

A popcan mortar with proper windage needs a bore of 2.667. 
A Diet Coke can is 2.6 inches in diameter.  (2.6/39)x40=2.667

Use Fg or even cannon grade  over 3/4 inch.

[Cat Whisperer]

bronzecannon --

WELCOME to the board!

I built my first beer-can caliber mortar in 1974.  They were different then - with the rim diameter being larger than the body diamter.  (Same as the current soup cans.)  In 1975 they introduced the rebated rims (took a little metal out of the can for economy).

SO, measure the diameter you wish to shoot.  Then apply the formula, as DD has stated, 1/40 the diameter of the bore should be clearance (windage); that leaves 39/40ths for the projo.  Do the math.

What do you like to shoot?

[Victor3]

 I had mine made to 2.635".

 Although generous windage had its reasons for mortars used in battle, it's not as critical on those made for hobby use. Less windage should (theoretically) provide a little more velocity with a given charge due to reduced blow-by.

 Some mortar makers use tubing stock that's already 2.750" ID from the supplier, so that's one reason some are that diameter.

 That said, I think it's wise to always stay with standard windage in any smooth bore cannon.