I understand that if I change ammo, it can change the point of impact (POI). When shooting .308 if I change from 147gr to 162gr there is usually a noticeable drop based on the bullet weight.
Today I had a different phenomenon when I changed ammo. The short story (I'll fill in the details below) is that I zeroed my new scope with one ammo, decided to test another, and the group moved 5" to the left (not "stringing", but a definite group in a new location). Huh? I can understand vertical movement based on hotter or cooler loads, or different bullet weights, but moving horizontally?
Can anyone explain why this might happen? Is there anything "normal" about this?
The details, for anyone interested: I was shooting a DSA SA58 Para 18", with a 1-4x AccuPoint scope. I zeroed it out to 100 yards with 147gr. Lithuanian 2004 manufactured non-corrosive brass cased ammo. It was a cold very foggy day, I was shooting at a 10" ring/target with a 5" shoot-n-see in the middle. All things considered, I was satisfied that the groups were about 4" at 100 yards (staying within the s-n-s). I changed over to some stuff I got from ammoman, that is advertised as "match grade" 168gr. M118 (manufactured by Igman). The groups were a little tighter... and the center of the group was a full 5-6" to the left, and 1-2" higher. Up and down I get, side to side I don't.
Today I had a different phenomenon when I changed ammo. The short story (I'll fill in the details below) is that I zeroed my new scope with one ammo, decided to test another, and the group moved 5" to the left (not "stringing", but a definite group in a new location). Huh? I can understand vertical movement based on hotter or cooler loads, or different bullet weights, but moving horizontally?
Can anyone explain why this might happen? Is there anything "normal" about this?
The details, for anyone interested: I was shooting a DSA SA58 Para 18", with a 1-4x AccuPoint scope. I zeroed it out to 100 yards with 147gr. Lithuanian 2004 manufactured non-corrosive brass cased ammo. It was a cold very foggy day, I was shooting at a 10" ring/target with a 5" shoot-n-see in the middle. All things considered, I was satisfied that the groups were about 4" at 100 yards (staying within the s-n-s). I changed over to some stuff I got from ammoman, that is advertised as "match grade" 168gr. M118 (manufactured by Igman). The groups were a little tighter... and the center of the group was a full 5-6" to the left, and 1-2" higher. Up and down I get, side to side I don't.