In .32 Long, I've been loading a Lee TL 90 gr SWC's. Red dot is working well, loaded using a Lee dipper and a trickler. Very tedious. Too light of a load for a UniFlow measure with that powder.
I forget what my loads for .32 H&R Mag are, but I keep very good notes.
If I were loading for accuracy, I'd be loading in the longest brass the chamber will accept. Less throat jump. One less variable.
With that much case volume, and the OP's desire for a light plinking load, I'd be tempted to play with Trailboss.
In fact, . . . , That sounds like a great project. I may try that.