I have a coworker who recently acquired a Winchester Model 12 shotgun with a 2-1/2" 20ga chamber. Sadly, the 2-1/2" shells are hard to come by and the modern 2-3/4" shells are about $40 cheaper per 250 and don't have to be special ordered. So, he's looking at getting the thing re-chambered for 2-3/4 shells.
He's not concerned with any potential loss in value involved, he just wants to be able to shoot it.
Are there any smiths who have experience with this sort of thing? Can you speak to whether it will be safe to make the change (he's only planning on shooting skeet, so it probably won't see much in the way of stout loads), and how much that may cost?