lyle2231
Well-Known Member
Depending on wind velocity? We know at least 4".
Dead on at 100yds 4inches right at 400yds
- Thread starter buzzyb
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Hugnot
Well-Known Member
I see - 3 pics, 2 shot at 400, 1 at 100. The 400 yard groups shows holes to the right of the target and one measures about .5 left-right and the other 4 inches left-right. If the averages of x and y coordinates of both groups were taken the center of both groups would be to the right side of the target and would probably be only 1 inch difference apart left-right and about .25 inch difference up-down.
Stuff happens and there are a huge variety of factors in play, like wind, some of which have been mentioned here. Possibly the issue of checking out your scope level might be re-examined. Also, some scope reticles/adjustments have been shown to being not exactly plumb (up-down) and upon making an elevation adjust the impact point might be shifted left/right. The one hole, 100 yard group was to the left of the target center. Possibly, another scope might be used and everything redone. Reticle centered before leveling?
Pages 140-144 of the Berger manual gives some info on the statistical stuff.
Stuff happens and there are a huge variety of factors in play, like wind, some of which have been mentioned here. Possibly the issue of checking out your scope level might be re-examined. Also, some scope reticles/adjustments have been shown to being not exactly plumb (up-down) and upon making an elevation adjust the impact point might be shifted left/right. The one hole, 100 yard group was to the left of the target center. Possibly, another scope might be used and everything redone. Reticle centered before leveling?
Pages 140-144 of the Berger manual gives some info on the statistical stuff.
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lyle2231
Well-Known Member
Give Sierra a call, speak to a tech, they are friendly and helpful.
greenejc
Well-Known Member
Again, the drift is almost perfect for a 2.5 to 3.5 mph wind left to right. If it were your shooting or the scope you'd see different and decided changes in both group size and impact point. This is a less than 1moa group at 400 yards, dead on elevation and consistent with a wind drift of around 2.5 to 3.5 mph. The wind might not even be at your shooting bench, but starting at 50 or 100 yards down range. You'd only recognize it with the use of range flags.
My guess is if you went and shot at 100 yards to verify zero Without touching anything you will find a variance of up to .1-2mils depending on the day and depending on the rifle, but mostly depending on the shooter variables, hold, trigger, cheek weld etc...
you can chase the perfect zero but tomorrow or the next day it might be different.
you can chase the perfect zero but tomorrow or the next day it might be different.
Ranger Rick
Well-Known Member
Every rifle barrel has either a right hand or left hand twist, and the spin of a traveling bullet from barrel twist has very minimal effect (even less than "a little") on horizontal spin drift at 400 yards i.e. definitely not up to 1.0MOA (= 4") @ 400 yards. Realistically, spin drift is not a factor in buzzyb's "shift" problem when his 100 yard zeroing shots are ~ 0.4MOA to the left = the opposite direction of a right hand spin effect and the opposite direction of his 4" shots to the right.
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Jake Suttles
Member
I believe some of my best practicing comes without firing a round. If you want to know what you are doing wrong and fix it dryfire practice is invaluable. Set up to shoot and dryfire 20x for every shot you actually fire.
Ranger Rick
Well-Known Member
With your 100 yard zeroing shots slightly to the left of the bullseye and your 400 yard shots to the right, spin drift is not the problem. Have you contacted Nightforce? NFhas a reputation for excellence, especially with its ATCR scopes. Plus, you can also contact other optics companies.
best guess if no wind is scope is not plumb.
If wind wasn't an issue, I'd bet that your rifle can't is off, it doesn't take much to be off 4in...
I recommend always using a scope level, not just eyeballing it.
Mike Matteson
Well-Known Member
From what I can see you are not zero @ 100yds. Your are about 1/2 to 3/4 inch to the left, which isn't dead on at a 100 yds. Nice group, but not zero. That doesn't explain the shift to the right at 400 yds. Rifle twist does play into the shifting of the bullet in one direction or the other. The grouping at 400 yds isn't what I call real good. Not sure of scope power, trigger control, That where I like a higher power scope when working up loads, and better target picture and what you are going on the target at different ranges. Once your scope rings is properly aline with the barrel changing out the scope shouldn't be a big problem. Barrelnut picture show you a problem on the mounting of the scope. Burris Xtreme Tactical Signature Picatinny-style Rings maybe a way to go. I don't presently have Burris rings yet, but on my next rifle I will try them out. So maybe somebody else can fill you in on that. In the past I use one pieces Leupold scope mounting rail. There is adjustment at the rear of the rail to shift the scope one way or another. I never had a problem with them. that would be cheaper than the Burris mounts.
Ranger Rick
Well-Known Member
Your custom rifle and scope plus your hand loads & shooting rest system should produce a consistent sub-MOA shooter, I'd be puzzled also. Have you let another person shot your rifle right after you have shot a 3 or 5 round group?
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Agree...99% sure this is your issue. Make sure your rings are true and mounted the same exact direction (bolts/nuts on the same side) If you center the windage turret, you should be fairly close to center in my experience. If you are having to dial a turn off center to get to your shot impact at 100 yards then you likely have the scope (Or rail) somehow mounted crooked. You impact variance to the right will keep getting worse the further you go out. Right now I bet is is 1" right at 200, 2.5" right at 300 etc...
