I'll tell you something that's funny. Frustrating too. With that Rem 700 I mentioned here, after a lot of work I had a load using CFE-223 and the 62 grain SMK that shot 1/2" at 100 yards consistently. I loaded and fired many of these, going through two pounds of the powder I bought (iirc) two years ago.
I used up all that powder. I bought a new pound of it a couple weeks ago. I just loaded some rounds, everything the same...brass, primer, bullet, charge weight. Groups are 2 1/4" at 100 yds.
Back to the drawing board.