Why would anyone lengthen a chamber when simply having forcing cones lengthened produce the desired result in most cases with probable better performance?
Erik, if "the desired result" is reducing pressure to what you'd get by firing a 2 3/4" shell in a 2 3/4" chamber, the only way to do that is with a 2 3/4" chamber. Sherman Bell's "Finding Out for Myself" tests showed that lengthening the cones usually resulted in some reduction in pressure. However, pressures still remained higher than when the shell was fired in a chamber of the appropriate length. It was usually only a question of a few hundred psi, but still higher.
Of course the tradeoff is that removing metal from the chamber (as opposed to just lengthening the cone, which removes very little metal) obviously weakens that area of the gun. That's why the Brits insist on reproof when chambers are lengthened.
