Originally Posted By: revdocdrew
GJZ: I can personally testify that the recoil in my less than 6# 1928 20g Trojan with chambers 2 7/16" using factory 2 3/4" Win AA 7/8 oz. target loads was absolutely brutal, and obvious to everyone observing on the skeet field. The perceived recoil with 1 oz. 2 3/4" 1150 fps. 16g loads in my 2 9/16" chambered 6 1/2# LC 16g was clearly less after lengthening the chambers. 1 oz. 2 3/4" target loads in my 2 1/2" chambered No. 2 frame 12g Trojan weighing 7 3/4# felt no different than 1 oz. 2 1/2" shells.
But my anecdotal data may not apply to other's experience, as I have a terrible flinch and am very recoil sensitive.


Drew, as Joe Wood's example of a Parker hang tag illustrates, it was not unusual for American gunmakers to recommend the use of longer shells in shorter chambers. In fact, as reported in a two-part article in The American Rifleman in the 30's--written by a man named Curtis who had worked for most of the major gunmakers for about 40 years--some American gunmakers intentionally short-chambered their 2 3/4" marked guns, because they found that slightly longer paper shells in slightly shorter chambers improved patterns. That's because, without the advantage of a plastic wad, one of the problems with deformed shot came when the shot charge exited the shell and came in contact with the barrel. If the case mouth opened slightly into the forcing cone, that offered some protection during the period of initial contact. It's no longer a factor, with plastic wads, but Curtis experimented with a Marlin 90 (starting with a 2 1/2" chamber) and found that the pattern percentage dropped as the chamber was lengthened.

Bell's experiments indicated that lengthening just the forcing cone--not the chamber--often resulted in a pressure reduction of as much as a few hundred psi.

The Brits regularly recommend the use of 67/67.5MM hulls in 2 1/2" chambers. This usually works out fine because the shells are loaded to CIP pressure parameters. However, both Thomas and contemporary writer Charles Fergus reported increased recoil and blown ends on hulls in older guns (I think all pre-1900) with very short and sharply angled cones. Using true 2 1/2" shells solved the problem.

One can always err on the side of caution, but even the SAAMI guidance posted earlier won't keep you totally out of trouble, unless you know how to interpret foreign proofmarks. There are certainly instances in which factory 2 3/4" shells should not be fired in guns with factory 2 3/4" chambers. It's unfortunate that it's not that simple, but unless you're talking strictly US guns and US shells, it's not that simple.