Joe, Unlike days of old when 2 3/4 shells loaded did in fact measure
2 3/4, todays 2 3/4 shells measure; 2 1/4 inches loaded and 2 5/8 fired! When we consider the difference in shell case thickness Card vs plastic; the modern 2 3/4 shell can enter the forcing cone of a 2 1/2 chamber without any meaning full restriction. This is why you do not see any evidence of case fraying.
My long standing concern is that many users of 2 1/2 inch chambered English guns do not realize that there is a maximum pressure limit designed into such guns. Extending the chambers of a 2 1/2 inch chambered gun to 2 3/4 [removing metal ]dose not make them safe to shoot 2 3/4 shells that develop higher breech pressures.
