Recently there was a lengthy discussion of forcing cones and lengthening them. I believe that reaming a chamber has the potential to thin the barrels in the most dangerous place while lengthening forcing cones does not. That is not intended to imply that lengthened forcing cones have any real value. Are these guns from England? If so reaming the chambers invalidates the proof while forcing cones is a grey area. If they were my guns, I would not ream the chambers, but find suitable low pressure loads commercially even if they're 2 3/4.