Nightforce correction factor

[Brambles]

I was shooting at 690 and 942 the other day with disappointing results, pretty much my fault for not compensating for spin drift. After I dialed the drift I hit the 690 consistently...but the 942 was a bit more challenging....something wasn't jiving with my solution...

it seemed like I was getting a bit more drift than predicted, so rechecked my level, found it a slight bit off.....then went and shot a tall target test..

This is where I found out my nightforce needs to have a correction factor.

Shooting at 100 yards ....Leica 1600

10 MOA dialed (expected 10.41)equaled 10.75" = .966 c/f
20 MOA dialed (expected 20.94)equaled 21.625"= .974 c/f
30 M0A dialed (expected 31.41)equaled 32.5"= .968 c/f

So I rounded the c/f to .97 and imputed that into shooter...

Which now is gonna make me change my velocity validation since the inches drop is off now....moving from 2750 fps to 2716 fps seems to bring the data back in line....I use a chrono very little since it's not an expensive unit and I thought it was lying to me...IIRC when I was chronoing this load during development it said 2716 fps....lol...quite a lesson on having the proper inputs....

The screwy C/F was causing me to think my velocity was higher than it actually was when I did previous velocity validation..


Is this a typical acceptable nightforce correction factor ?

 

[ShtrRdy]

Most people don't have any trouble with the tracking on a Nightforce. Which model scope are you using?

I'd question the accuracy of the Leica 1600. You might try making a target with hash marks or 1" orange dots spaced every 5 moa at 100 yds. Then from 100 yds, lay the reticle over the target and see if the hash marks on the reticle look like the right spacing.

 

[bigngreen]

I won't use a rangefinder for optic tracking but use a tape and put 300 ft 0 inches to the turret from the target face. I don't shoot for turret calibration, there are few guns that actually shoot zero's so you will be of some amount so your stacking tolerances now. Parallax is absolutely critical especially as touchy as it is on a NF, in dozens of tests I'll usually only run a .005 +- correction from true MOA on a NF.

 

[Greyfox]

My G7 NF 5.5x22x50 NXS scope that I tested for tracking at 100 yards to 30 MOA was less than 1 percent variation.

 

[Brambles]

Most people don't have any trouble with the tracking on a Nightforce. Which model scope are you using?

I'd question the accuracy of the Leica 1600. You might try making a target with hash marks or 1" orange dots spaced every 5 moa at 100 yds. Then from 100 yds, lay the reticle over the target and see if the hash marks on the reticle look like the right spacing.

Night force nxs 5.5-22x56 npr1 zero stop.

 

[Brambles]

I won't use a rangefinder for optic tracking but use a tape and put 300 ft 0 inches to the turret from the target face. I don't shoot for turret calibration, there are few guns that actually shoot zero's so you will be of some amount so your stacking tolerances now. Parallax is absolutely critical especially as touchy as it is on a NF, in dozens of tests I'll usually only run a .005 +- correction from true MOA on a NF.

I suppose I'll have to take my tape measure out with me next time and manually pace the target.

 

[Brambles]

Well I just ran the math on the correction factors

.97, your guys .995 and 1.0

It certainly makes the most sense that I mucked up the correction factor test...something musta been screwy with my setup because the math ends up making my hits extremely close in elevation.



At 650 there is a 2.75" difference between .97 and 1.0 c/f
At 931 there is a 8.76" difference between .97 and 1.0 c/f

Considering I was approx .25 MOA low at 650 and a strong .75 MOA to a weak 1 MOA low at 931.... It seams as though this is the culprit....

 

[bigngreen]

These are hard to nail down unless you can positively nail down more factors, this stuff drives me nuts because a slight zero, a velocity and a turret correction all act very similar.
I built a test stand and grid for testing optics of the rifle and cab nail the correction factor, this was a huge improvement. A Magnetospeed was the next huge leap, if you know your velocity is within 10 fps of what your reading this really pushes the range out before tuning.
I find my zero is often the culprit, first I tend to shoot with a little different form when up close and really concentrating on that dot, second paralax is much touchier at close range. My solution is always zero at 100 then shoot 300 which is close enough speed, BC and turret won't be a factor.
Also
An other good tool to help validate data is just to shoot holding over with the reticle for gross movement then dial a couple moa so you can use a hash marks for a good hold, this will validate turret movement well.

 

[300 whby]

I have 4 Night force scopes 1. 5.5-22x56 Hi speed Zero stop, tracks perfect up to 80 Moa,
2. 8-32X56 hi speed Zero stop. Less than 1/4 Moa/ 10Moa across 50 Moa
3 8-32x56 Standard 10 moa turrents no zero stop has a correction factor .962 across 50 moa & it's pretty constant across the range.
4. 5.5-22x56 Varminter range finder reticle 1/8 moa adjustments,has up to plus or minus 1.moa across 40 moa
It's on a 22/250 A I , I use the reticle for holdover out to 500 mts beautiful crystal clear glass so I never worry about changing the turrents except to adjust my zero
probably a bit of wear.
Even with one scope with a small correction factor I think they are by far the best value for money scope, & also their factory backup service is excellent.
I think from memory the last top end scope test carried only showed 2 scope that were perfect tracking both well over $3000...