Have any of you seen a velocity difference in one jug of powder compared to another . Today I was shooting a mixed batch of shells some from one jug some from another. One group was an inch at 300 yards dead center another group was one inch but 4 inches low. The gun was obviously shooting sub Moa but my groups confused me and all I could this was that it was the powder? Btwn each shot I waited 5 mins and was very careful of my form and level..: any ideas??