In my 1894 cowboy 44 mag, 24" ballard rifling I found 8.5gr of Unique with a 200 gr Oregon Trail laser cast bullet, sized to .429 to be an accurate load (10 shots at 50 yds for a 2.5" grp) It's the load I've been using for Lever Action Pistol Caliber Silhouette.
That was last fall and 800 rounds ago. When my scores went down and and I checked with paper targets, I noticed larger groups than I expected. Going t the bench, I checked loads from 8.5 to 10.5 grains of Unique. 8.5gr had opened to 5.75" but 9.5gr was 2.75" (All with iron sights).
Powder and bullet lots had changed but I find it hard to believe that they would cause that much of a change in accuracy. It was suggested that Unique being a double based powder could be eroding the throat. I find that hard to believe since the loads are pretty light
Any thoughts as to what may have changed? BTW all groups were 10 shot and included "flyers"
Thanks
Ken