Montana - it is possible to find 2 1/2" guns with short forcing cones; which has more impact on hull life than on pressure. Lengthening forcing cones does not take a gun out of proof. Chamber lengthening does. I'm not aware of any 2 1/2" loads above CIP pressures. CIP loads are OK for all 2 1/2" nitro proof guns; true low pressure (so loaded or so marked) is kinder and gentler, though. While there are low pressure 2 3/4" American loads, you do have to know (shot charge weight is NOT an indicator of pressure) which ones and the factories have not been very helpful with data to date.
Ken - IMO, if AG sez it is OK, then you can be sure it is OK. Since you are a shooter-collector (as opposed to a collector-shooter or pure collector), the 2 3/4" rechamber isn't a major isuue (assuming you take the reduction in collector value discount up front). New/sleeved barrels always beg the question, "Why?" Judging the value of a gun gets tougher as we get into repaired/restored condition. Generally, we have a little birdie in the back of our heads that sees a battered old gun as "honest" and a restored one as somehow "shaddy." This, IMO, comes from our feeling more comfortable with assessing the condition of a battered gun than assesing the value of repairs/restorations; much like buying a car with a rebuilt engine, "Why did it need rebuilding, who rebuilt it, how do I know he did a good job, what else could be wrong?" New barrels can be had for $5000 to $10,000 and something like $20,000 at Purdey's. So, what is a Purdey with no/unrepairable barrels worth? My market model sez that a BV1-OQ1-CC5 (restored) = $12,000. New barrels by the maker might help that a little bit.
