Download the current PDF from Alliant. It lists a +P max load of 3.8grs of Red Dot with a Speer 158gr LSWC bullet at 846 fps. Data is good for all the Speer 158gr Lead bullets to include RN and LSWCHP's and is the same as what you find in the Speer manual.

A slower medium burn powder will add 10% to 15% velocity over Red Dot but Red Dot is perfectly useable if that is what you have.