Five shot groups will give more information. Along with that there is a couple of things you could do to improve consistency. Do index your sabots preferably to get 2 lands on each sabot, I find the longer the range the more difference this makes.
Secondly be careful to get the same setting pressure this can make a bigger difference than most people would believe. These two things alone can be the difference between a 1.5 inch group and a .5 inch group if you have control a good scope and decent form for rest shooting. Lee