It is worth looking back as to how the concern over shell length developed.In the era when rolled over shot wad was the method used for shell closure a loaded 2 3/4 shell measured 2 5/8 It normally contained 1 1/4 ozs, of shot and the appropriate powder charge.Likewise the 2 1/2 shell was 2 3/8 inches long it normally contained 1 1/8 ozs,of shot with a proportionally reduced powder charge. The chambers of the guns at this time were machined to correspond with expanded case length [2 1/2 or 2 3/4] At the same time, forcing cones were shorter in length than todays practice. In these circumstances it was absolute folly to attempt to shoot a 2 3/4 shell in a 2 1/2 chambered gun, always assuming you could force the action to close.
Most sportsmen of the day were well aware of the dangers presented by attempting to shoot 2 3/4 shells in 2 1/2 chambered guns , this concern has been passed down from father to son. Whislt this concern is still legitimate, the advent of the crimp closed case with its reduced case wall thickness and reduced closed length, has for all practical purposes eliminated the primary reason for barrel constriction caused by the shell case length. The remaining safety problem, one that has been repeatedly stressed by other comentators is control of breech pressure.," For your safety, use only shells that generate breech pressures within the allowable limits for 2 1/2 chambered guns!"

Roy Hebbes