Hi RL15 has basically the same burn rate as Varget so 44gr and a 175gr pill with a 26inch barrel I would say you are expediting them @ 2700 fps, I know mathematically 2 inches @ 500 yrds equals .40 @ 100 yrds, but there is a lot factors and things that happen in the following 400 yrds, so I can't actually put a number on how much smaller the grouping would have been @100 yrds, but I am willing to bet the farm that it was tighter than .40, I can only aspire to become a crappy shot like you one day ;D

Tanks Dean