1883 stepped 2 5/8 chamber
 

This gun has a bore measurement of .753 and a chamber that has no taper in a forcing cone. Have shot 2 3/4 shells with no noticable effect. Decided maybe 2 5/8 would be in order. I then got to thinking that with an oversized bore like this maybe 2 3/4 inch would be better. The crimp would overlap the step and make a nice transition into the bore. With the wad about .730 it seems to make sense to me. What do you guys think.

Chamber Dimensions
 

A 12 ga shell is .810 outer diameter; the paper is .030 (1/32) inch thick. The ID of the shell is .750 ; a perfect match for a .750 bore. Was this Parker's intention? or was it easy to obtain 3/4 reamers ? The tooling changed around s/n 70000.

Does anyone know when chamber taper originated?

Best, Austin

Austin, I always count on you to know those details!
Thanks for your assistance

Linn

Austin, I don't know when square cornered chambers were phased out, but I have seen Parker Brothers repair orders requesting that the square corner be cut out.