Steve,
I have accuracy tested three Stevens 44s with different barrels (Original, Green Mountain & Shilen Rachet). One with a "sporting" chamber & two with tight match chambers. I've accuracy tested the rifles with SK Long Range, RWS R50, RWS R100, Ekey Match, Eley 10X, Lapua Center-X amoung others with velocities ranging from 1070 to 1144fps. All three rifles prefer velocities around 1100fps or more for acceptable accuracy on the turkeys & rams. I don't have a theory other than to say that different rifles prefer different ammo which requires trying several brands of high-quality ammo over a range of velocities to find the velocity sweet spot.
Wayne