21.0gr of alliant 2400 and 240gr hornady xtps 1.60" oal, shoot good in my redhawk. 1500fps average velocity. of course the 14" barrel should be faster. i don't see why most magnum primers wouldn't be fine. i use federal, and have used cci. the cci mag primers are harder cups and i have some misfires in the redhawk.
make sure you get a good crimp. the slow pistol powders need it for good ignition, so i've heard anyway. h110 should be a good powder, but havn't had the need to try it since the 2400 handles my needs just fine.
