I shot five groups at 100 yds with 69 SMK, and 24.0, 24.4 and 24.8 of RL 15 powder in my Tikka Varmint 223. The 24.0 was one hole 3/8th inch, the 24.4 and the 24.8 were both 1/2 inch. No vertical or horizontal stringing. How can that much of a spread in powder all shoot the same ? How to I pick which load to use ?