I took some 20 ga Remington Gun Club (same innards as Remington Premier) and cut them to 2 1/2". Followed receipe on the Alliant Powder site using Unique powder 13.4 grs, 7/8 oz shot Remington 209P and Remington RXP 20 wad. Velocity 1,050 and 7525 psi. The bushing for my Mec was throwing more so I reamed out another bushing to throw 12.95 grs. Temperature was in the mid 30's today and shells worked great. Looking through reloading data between Alliant and Hodgdon there are quite a few loads using Ferderal shells and only 2 for Wincester. Remington had only this one. I have quite a few 20 ga Rem. Gun Club already cut down, and the ones I fired today look good enough to use again. The mouth of the hull has to be widened, but so do the cut ones a little. Finished shells are the same size as a 2 3/4" shell fold crimped. The actual size of 2 3/4" shells fired was any where from 2.407-2.710. Here are a couple results.
20 ga Field Grade circa 1927 28" barrels full/full, 3 position safety.