I don't have a "Deerfield", but I do have an older, original model Ruger semi-auto carbine in .44 magnum.
I have had good success with a maximum load of 24.0 grains of Hodgdon's H-110 behind a 240 grain Nosler JHP bullet. This load generates 1817 fps out of a 20" barrel with 36,200 CUP.
In their "freebe" handout (at most reloading equipment dealers) "Basic Reloaders Manual-2003", Hodgdon WARNS that their H-110 powder should NOT be reduced MORE than 3% from their maximum listed load (24.0 grains). Doing the "math", this means that you can reduce their maximum load (24.0 grains) by only .72 grains yielding a "starting load" of 23.28 grains... a very "narrow" powder weight range.
Strength & Honor...
Ron T.