not inconsistent ignition. Ive dealt with the same thing. One powder likes one primer and shoots great, the next primer makes it shoot horrible. CCI 209s shot horrible in an Optima that i owned. Winchester 777s shot excellent 3 shots touching @ 100 yards. Thats why i always tell the new shooters to buy a package of each 209 primer that the store has in stock and just work up a tight load, then change the primer and see how accuracy goes.

Good that you got her sighted in though. Im sitting here right now loading up another shot for my kentucky. God awful groups at 100 yards! Im back at 50 yards adjusting sights.