Andrew:
I've had great success shooting low pressure (sub-7500 psi) 2-3/4 inch reloads in 2-1/2 inch chambers. I use the data out of the Lyman reloading manual and have found that Clays powder lets you get a load that is low pressure with 7/8 or 1 ounce of shot.
If you measure your fired hulls, you'll find some of the nominally 2-3/4 inch hulls are more like 2-11/16 inch or even slightly shorter. The crimped section does not extend the entire length of the forcing cone, which I think would help keep pressures lower than a longer hull might.
Winchester AA hulls seem to be the shortest of the hulls in my assortment, but I don't load Federals or Cheddites, except in 10 gauge, so you'd have to check them to see how they might measure.
Rem
That’s the logic I was kind of operating on, but turns out they already were reamed to 2-3/4. Took it up to the gunsmith after work and they measured and confirmed. Makes loading easier for sure.
