Why not just use 2 1/2" shells in 2 1/2" marked shotguns? They are readily available, same with hulls and components. Even discarded inexpensive 2 3/4" Euro hulls can be had for free and cut down. Mec makes adaptors for their reloaders to load 2 1/2" shells. I have Mec's in 16ga and 12ga set up for 2 1/2"
I don't even bother with 2 3/4" shells any longer, 2 1/2" shells work just fine in my 2 3/4" guns and I never have to sort through shells to make sure I have the correct ones. Even all my waterfowl loads are in 2 1/2" using ITX or Bismuth. The only 2 3/4" loads I do any longer are 1 1/4 ounce coyote loads for my combo guns.
I doubt there are many 2 1/2" chambered shotguns used for really high volume shooting where loading or buying 2 1/2" shells would be problematic.
