I'd stick with the 240gr/260gr bullets also. The shorter/lighter 44cal bullets do extremely well in the short bbl'd/snub nosed revovlers (3" or less). Your 4" bbl should be around 1400/1450fps with 220gr bullets and 1300fps with 245gr lead/cast/coated bullets. Jumping up to a 260gr bullet will put you in the 1200/1230fps range.

You'd be better off using 2400, aa#9, h-4227 powders. A lot less flame cutting with them compared to h110/ww296.

fredj338 has excellent advice as usual. A 240/250gr lead bullet doing 1250fps is a fearsome load.