I have used many different powders in the 243. Many displayed inconsistencies so were eliminated from further testing. IMR 4350, H4350, AA4350, IMR4831, RL15, and H414 all showed consistent velocity and accuracy. No one powder was really any better than the others.
I have settled on AA4350 because of 55 gr., 70 gr. and 100 gr. bullet performance. I use a 1967 Rem 700 Varmint special and a 90's Rem 700 VLS. Both fitted with Jewel triggers set at 1 lb. with pillar bedded stocks and epoxy bedding.
I find the 243 an excellent varmint and deer slayer. Fun to shoot without kicking the fun out of it! Been shooting this caliber for 50 years and have never tired nor been disappointed.
Matt