Jack,
Your gun is probably 2 1/2" chambers also. I know a lot of people hear say it is alright to shoot 2 3/4" shells out of it, but why take the chance. RST and a few others are making low pressure, low velocity 2 1/2" loads for these old guns.
Also if you are using 2 drs. black powder , the same would be true for smokeless, 2 dr. equivalent.
I have reloaded some Remington Game Loads, Gun Clubs,(same insides as STS, Premiers) cut down to 2 1/2" using Unique powder but with 7/8 oz shot, 7525 psi and 1050 fps. Roll crimped. I haven't tried any out yet so can't verify anything.
This load was tested in 2 3/4" 6 crimp, so the 2 1/2" hull takes up the same area with the roll crimp as the 2 3/4" 6 crimp.
