Re: HELP velocity difference
Shoot at a target at least 400 yards away and see if vertical stringing is apparent.
Chrono each shot. This should tell you something.
If groups show no vertical stringing then the chrony is suspect.
Otherwise it may well be the powder charge and primer combination.
If the load is on the very very mild size, that is, not much powder in the case, powder geometry differences may be the problem. I have absolutely no feel for the 243 cartridge and 4895 thus I don't have any idea of how hot your load is.
100 fps is a quite large extreme spread. Unheard of around my place.
Just some thoughts......
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