The place to start is with the rifle data. Intuition would lead one to believe that the faster powders would work better in a shorter barrel but this isn't necessairly so. The Hornady and Barnes manuals I use (among others) frequently give the names of the powders they had the best success with; those are the ones I would start with.
If you call T/C, they'll tell you the twist rate of your barrel. Bullet boxes I've gotten from Hornady show the twist rate the needed to stabilize the bullets. Since velocity will be lower than in a rifle, I would try lighter bullets at least initially but you may find that heavier bullets will stabilize as well.
The Hornady manual also lists many loads that were worked up in Encore handguns (I don't know if the 25/06 is one of them). It could at least give you an idea of what powders they thought useful in similarly sized cases.