George - I bought a beautiful Westley Richards from Jack Dudley's La Becasse (second location)10 years or so ago. The chambers were rebored to 2 3/4" and then re-proofed, sometime in the eighties.
In our discussion about the gun Jack opined that it was probably done because the Brit was planning on shipping it to the US and thought this chambering would make it more popular here.
Whatever the reason, British guns can be rebored and proofed again for that length. This would be in keeping with the legality of shipping them here.
I hope I'm not coming off like I'm shaking a stick at you as if you were wrong. Not at all! I agree with you, I wouldn't trust an old Brit gun that was proofed at 2 1/2" and had longer chambers.
My only concern was to point out to the original poster that a gun can always be proofed, again and again if needed or desired. Longer chambers are OK to trust on an old English gun providing the gun has the corresponding proof marks.
This obviously doesn't apply if the gun has gotten abused in ways that would make it an unsafe gun.
