Sureshot ...
My 2 favorite cartridges are the .45lc and the .243. I shoot these a lot at the range and keep very detailed records. I have not been reloading very long compared to some of these other guys but I have found the following to be best for my firearms:
.45lc - I use the new, cleaner burning Unique for my Vaquero and Marlin with 250gr bullets
.243 - I use Varget with the 3 different bullets I shoot in my Ruger M77. These are Hornady 65gr V-max (best group so far is .500"), Sierra's 60gr HP (best group so far is .410"), and my favorite bullet is the Nosler 70gr ballistic tip (best group so far is .147".)
Again, I have tried some other powders but not very many.