I can tell you that I use a short 30 grns of Swiss Fffg in a rifle with a .40 cal GM barrel and it is an excellent load for squirrels. I say a short 30 because I use a flask with a spout that throws a bit shy of 30 grns, probably 27-28 grns. I also have a .32 cal Crockett rifle that shoots great with a short 20 grns of Swiss Fffg(a different spout). I would think something between 20-30 grns would work fine for your rifle. It doesn't take much to kill a squirrel and most shots are fairly short.