2" =2.500" = 63.5mm
2 9/16" = 2.2.5625" = 65.09mm
2 5/8" =2.625" = 66.675mm
2 3/4" =2.750" = 69.85mm
2 7/8" = 2.875" =73.025mm
3" = 3.00" = 76.2mm
As long as the chamber is long enough the crimp is not jammed into the cone & the cone is long enough the diameter at end of hu8ll is not restricted by about .75m (.030") below end of chamber diameter the the important thing is not the actual length of the hull BUT the Load therein.
Speaking here primarily of British proofed guns those proofed for 2 3/4" are proofed heavier than those proofed for 2" loads. The heavier loads should not be fired in the lighter proofed guns regardless of what length of hull you manage to put it in. Far, Far better to fire a 2" load in a 2 3/4" hull than to fire a 2 3/4" load in a 2" hull.
