Posted: 9/13/2014 11:56:23 PM EDT
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Is this normal?
Put a new scope on my 300 win mag today and was sighting it in. I like to use a cheaper ammunition like blue box federal SP's and then dial it in on whatever premium hunting ammo I am using. In this case I was using Federal power shock SP's to get on paper and then Barnes Vortex to get dialed in. Both were 180 grain loads. At 100 yards there was almost 7 inches of difference in the POI. Now I have used this method a time or two before on different rifles and I know there will be some difference in POI but 7 inches? That seems extreme, I usually get 3-4 inches max when using the same weight bullet. Both brands grouped well out of the rifle both were grouping sub 1 inch at 100 yards, all the shooting was done off the bench from a vise, and I was apple to replicate the POI shift on three separate three shot groups respectively (so six three shot groups, three from the Federal and three from the Barnes). All of POI sifts were uniform. When zeroing for the Barnes the Federal grouped two inches higher and five inches to the left. |
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Quoted: Is this normal? Put a new scope on my 300 win mag today and was sighting it in. I like to use a cheaper ammunition like blue box federal SP's and then dial it in on whatever premium hunting ammo I am using. In this case I was using Federal power shock SP's to get on paper and then Barnes Vortex to get dialed in. Both were 180 grain loads. At 100 yards there was almost 7 inches of difference in the POI. Now I have used this method a time or two before on different rifles and I know there will be some difference in POI but 7 inches? That seems extreme, I usually get 3-4 inches max when using the same weight bullet. Both brands grouped well out of the rifle both were grouping sub 1 inch at 100 yards, all the shooting was done off the bench from a vise, and I was apple to replicate the POI shift on three separate three shot groups respectively (so six three shot groups, three from the Federal and three from the Barnes). All of POI sifts were uniform. When zeroing for the Barnes the Federal grouped two inches higher and five inches to the left. Hard to say if you don't have the load data. Same bullet weight wouldn't make much difference if one load was hotter than the other. Just my opinion, not an expert. |
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Anytime you change anything in a load, you are likely to have a change in the point of impact. Different bullets, even of the same weight, different brand of primer, different powder, sometimes even different brass, point of impact can change, sometimes a little, sometimes a lot, there's no predicting it, which direction or how much. In commercially loaded ammo, the same ammo but from a different lot might have a different point of impact, the manufacturer might have changed the powder, or maybe the bullet maker made some change in the bullet. |
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Absolutely normal, multiple factors at play due to different brands of ammo: possible use of a different powder (more than likely...one powder burning faster than the other); bullet seating depth is likely different, and the other variable would be the shape of the bullets used between the two different brands. The seating depth and bullet shapes are relative to each projectiles' proximity to the lands in the rifle, which can increase/decrease pressures.
All of these factors would combine to make one of the brands faster than the other, which would cause a POI shift. |