Believe it or not, some revolvers are really picky about the loads you put in them.
Try out a control load. 250 grain LSWC, sized to .430 inch, on top of 8.0 to 8.5 grains of Unique.
This is the accuracy load for the .44 magnum developed by Elmer Keith. It is a nice load--not too much recoil or muzzle flip. With this load, my Model 29 will shoot well within 1 1/2 inches at 25 yards from a rest with irons. If the pistol doesn't like that, chances are it won't shoot anything well.
Hiding in plain sight...