I had the same problems with a 54 cal and sabots, about 200 rounds later, I found that if I lubed the barrel for the first shot, it moved the saboted bullet 7"s to the right, bact to the same impact point as the dirty barrel. I was using natural lube 1000........[lightly lube, load, then slime the heck out of the barrel]...also in hunting season, if you leave the gun loaded, you need to swab the barrel with lube, about every two days!

As they say, Your Results May Vary!