I found this article interesting,I don't think I will bother fire forming prior to load develpement(why waste bullets and barrell life?).Safari Club International - Detroit Chapter
"... I did notice a difference in POI on target by about 1" between virgin and fired brass."
Sure wouldn't ever say anything CAN'T happen, it just hasn't happened to me. At what range did that 1" impact shift occur?
I first discovered it at 100 yards, and it was consistent. One lot of brass, I shot some once fired next to virgin brass, and the POI was 1" off. Can't remember if it was high, or low, but it was almost exactly 1" off vertically on multiple range trips.
Interesting. What did it do after being reloaded? (If you've gotten that far.) I mean, wonder if it will stay there or move back to your old zero. ??