Max charges using Hornady .310" 123gn FMJ bullets. Hornady - 23.9gn Lyman - 25.7gn Western - 27.3gn Speer - 28.2gn (using Speer bullet, not Hornady). I decided to work up loads from 23.0 - 27.0, in 1.0gn increments, 3 rounds each charge, just to get a ballpark idea for now. This will primarily be for a 16" AR, but I also have a Ruger Mini-30 (and, yes, it has a .310 bore). Anyone have a pet load in x39 using 1680 powder? I also have some Berrys plated .310 bullets to try as well.