During load testing I came across two different powder charges that gave about .5" to .75" of vertical at 300 yds but about 3" of horizontal. The amount of vertical spread was nice and both of these groups were around the same powder charge that yielded the smallest groups so far during test.
40.5 imr 4350 2.800 coal 1.153" CTC 3 shot group


41.5 imr 4350 2.800 coal 3.301" CTC 3 shot group not much vertical spread


44.5 imr 4350 2.795 coal 1.806" CTC 3 shot group .816" vertical



45.0 imr 4350 2.795 coal 3.658 CTC 3 shot group .455" vertical


All groups shot at 300 yds. So what causes this much horizontal spread? Was going to load some up between 44.5 and 45.0 to see if a happy medium can be found.