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