ronn, sounds like you have LOTS of experience handloading. One powder that my friends and I like, especially for magnums, is H4350. It is close to and shoots like IMR 4350, but it's said by the manufacturer to be temperature resistant, so it shoots the same in any season. RL19 has always been a tack driver for us too. A brand new powder, which I haven't even been able to find yet, is Hybrid 100V. It's supposed to be very accurate and work very well in powder measures - runs through the measure consistently even. Keep in touch.