Today I shot some M193,Q3131A and Winchester 45gr varmit ammo, scoped at 100 meters, from a bench rest. The winner was the 45gr Winchester, printing one hole with an occasional flyer. Second, was the XM193 with all shots touching each other. The XM 193 printed 1-1.25 inches like the smile of a smiley face. Third, was the Q3131A which gave a veritcal 1- 1.75 inch string and occassional flyers.

I then took off the scope on my flat top and mounted a detachable handle and shot with peep sites. All shooting still was off a rest. The order in how the various ammo performed changed and I don't know why. The winner was the Q3131A, printing 80% of the time in a two inch group. Second, was the XM193 which didn't shoot as tight a group as the Q3131A and measured about a 2-3 inch in group size. Third, was the Winchester 45gr varmit which would give a 3 shots touching group then throw 3 other shots 4 inches away north, south east or west.

What's up?!!

How did Q3131A go from last with a scope to first with iron sights? How come the varmit round went from a one shot dead center round to last place?
Thanks,
Anthony

barrel vibration?  Changes due to changes in system harmonics?

I shoot better with open sights than I do with scopes.  Don't know why.

PaDanby, you know, your probably right!! The weight of the scope could be changing the harmonic vibration. I wonder if a weight was put in the butt stock what would be the effect?
Thanks,
Anthony