The well informed responses to my post have convinced me that I've been wrong in my opinion about chamber lenghtening. Well mostly wrong anyway. What bothered me are the following facts. SAMI allowable service pressures for 2 3/4" shells are nearly 2000 psi more than CIP pressures for the same length shells. So a 2 1/2" gun is deepened and reproofed to CIP standards. Exported to the USA and then used to fire SAMI shells. Where is the sense in that? The gun has been weakened to allow the use of higher pressure shells. Wouldn't it have made more sense to just lengthen the forcing cones? No doubt the people who do this work have measured the barrel contours, etc. and have concluded there's metal to spare, well maybe just eyeballed it but what the hell, it's only a quarter inch. Don't get me wrong, when I was a kid I made 12-bore shotguns out of 3/4" iron pipe slid inside a 1" piece. Killed as well as a H&H Royal. It's just that in my dotage my opinions are less and less rational. I'm glad I can count on the folks here to help me keep a grip on reality.
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