Virgian brass vs fire formed

[schrock27]

I am not sur if I am posting this in the right place or not but I will ask it anyway. I was at the range a few weeks early and had a good shooting session. I was shooting two and three times reloaded norma brass out of my 7mm mag. Went back to the range yesterday and notice that after about 350 yds I was hitting low. At 1000 about a moa low. I was shooting brand new norma brass. Could this be the reason I was hitting low?

Thanks
Anthony

 

[Broz]

Formed brass typically shoots a little faster for me. But I doubt very much it was a full moa.

I would recheck zero and then confirm zero at 100. Then confirm zero at 200 or 300 to get out past the evil 100 yards parallax.

Also in bad mirage I typically shoot 1 moa low.

Jeff

 

[schrock27]

Thanks for the info! I did check zero 100 before I headed out to the longer shots and everything seemed to be fine. I worked my way out from 100 to 200 to 300 ect... Out to about 700. At about 400 I saw that I was hitting the bottom third of 10 inch steel disc. And the farther I got out the lower I got. At 700 I just caught the bottom of the disc.

 

[Broz]

Thanks for the info! I did check zero 100 before I headed out to the longer shots and everything seemed to be fine. I worked my way out from 100 to 200 to 300 ect... Out to about 700. At about 400 I saw that I was hitting the bottom third of 10 inch steel disc. And the farther I got out the lower I got. At 700 I just caught the bottom of the disc.

If, you have accurate muzzle velocity and accurate BC info for the bullet, and were already off program at 400 yards by .5 to .75 moa. I suspect mirage or a parallax issue at 100 yard zero. If there was no mirage, I would confirm a group at 200 or 300 to match program. If not on, use the zero height adjustment in the program to get dead on at 300 with the program. Then retest on out.

Jeff

 

[el matador]

The effects of virgin brass seem to vary quite a bit. I would think that the somewhat more "roomy" factory chambers will see the biggest difference. 1 MOA of elevation is probably 40-50 fps, which is quite a bit, but not unheard of. If you have a chronograph you would be able to tell for sure.

 

[schrock27]

Thanks for the replies guys. I did some shooting at my house last evening and found that my zero was in fact off I was about .75 moa low at 100 yd. I must have lost zero after I started shooting.
Thanks
Anthony