Range Report Problem: POI hitting 20" low @ 1000

[Alan Griffith]

Where to begin?

Surgeon
26" Krieger 1:8.5
NF 5.5-22
AICS 1.5
6.5x47 Lapua
40.8 gr H4350
Berger 130 VLD
CCI 450
Approx 1100 rounds down barrel.
Lapua 8x fired brass, just annealed 2x. (anneal every 4th shot)
2821 fps verified last week with 20 rds in similar temps 70 deg F, 24.5 baro
Shot to 600 yds last week with impacts every 100 acceptible.

Yesterday.....
70 deg
23.4 baro
my come up via Shooter on my DROID was 23.8 MOA(G1) and yet POI was 20" low; two full MIN. Group was 5" or 1/2 MOA. Yes, I did underestimate the wind as it hit 9" left of center.

Any ideas on what could cause this? What comes to mind is

1. Berger BC not accurate
2. Zero could be tweaked a bit but wouldn't it mean I'd be 2 full MOA off @ 100?
3. Freshly annealed case might have lowered vel though my last annealing changed vel by 4 fps and a 2.2 SD improvement.
4. Last weeks 600 yd group shot from plastic folding table. Yesterdays group shot prone on concrete @ shooting line. Harris 6"-9" bipod, both groups.

Also, my hits to 600, in 50 yd increments, were spot on.

HBO = help a brother out?

Alan

 

[Nate O.]

Re: Problem: POI hitting 20" low @ 1000

what is your elevation?

Might not hurt to dial in your 1000 yrd dope and shoot it at 100 just to make sure your POI is where you expect it to be.
Doubtful your NF is acting flakey, but you never know.

 

[BobinNC]

Re: Problem: POI hitting 20" low @ 1000

Alan,

Run your calc's on JBM. There is something wrong with the come-up's from your droid.

 

[Alan Griffith]

Re: Problem: POI hitting 20" low @ 1000

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Nate O</div><div class="ubbcode-body">what is your elevation?

Might not hurt to dial in your 1000 yrd dope and shoot it at 100 just to make sure your POI is where you expect it to be.
Doubtful your NF is acting flakey, but you never know. </div></div>

Nate,

When I zero'd the week before; 4900' elev, baro 24.5, temp 70.

Yesterday, 6565' elev, 23.7 baro, temp 70.

When I get out next, probably next Saturday, I'll check my zero again.

Alan

 

[Alan Griffith]

Re: Problem: POI hitting 20" low @ 1000

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BobinNC</div><div class="ubbcode-body">Alan,

Run your calc's on JBM. There is something wrong with the come-up's from your droid. </div></div>

Bob,

I'm horrible with JBM. So, not sure if my results are correct; BUT I did come up with 25.8 which is 2 full MOA different from my DROID (23.8) and I would have been "on" with JBM's results.

Maybe I'm horrible setting up Shooter?

I'll try to relay how I set up both.

Alan

 

[Nate O.]

Re: Problem: POI hitting 20" low @ 1000

I just ran my numbers through shooter using 140 vlds in my 260, and came up 1 moa less than real world @ 500 and 'bout 2moa short at 1000.. maybe something with the newest update. Or maybe i'm entering data incorrectly? I was using the G7 model.

 

[Alan Griffith]

Re: Problem: POI hitting 20" low @ 1000

I may have found my problem.

On Shooter, originally, I did NOT check the "Pressure is absolute" box yesterday. When I don't, and enter 6565' altitude, it comes up with 23.7 MOA. When I DO check the box the actual altitude of 6565' is automatically removed and the results come out as 26.1 MOA. Much closer to the results I'm looking for. It's about 5.5" different from the 20" I hastily measured yesterday. I was two thumb to pinky finger spreads (9" each) plus a couple of inches below the center of the B27 target. Problem with the B27 target is it doesn't have a defined aiming point and I was just aiming center mass.

Do you guys think I solved my problem?

Alan

 

[Alan Griffith]

Re: Problem: POI hitting 20" low @ 1000

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Nate O</div><div class="ubbcode-body">I just ran my numbers through shooter using 140 vlds in my 260, and came up 1 moa less than real world @ 500 and 'bout 2moa short at 1000.. maybe something with the newest update. Or maybe i'm entering data incorrectly? I was using the G7 model. </div></div>

Nate,

When I try the G7 BC, my results come up 21.1 MOA when "Pressure is Absolute" and 20.2 MOA when I enter the actual 6565' elev. So, neither, in the real world would work for my. I think I have to stay with the G1 BC.

Alan

 

[doc76251]

Re: Problem: POI hitting 20" low @ 1000

What your describing is the classic difference between IPHY and MOA in the scope knobs. Calibrate your scope.

Cheers,

Doc

 

[Alan Griffith]

Re: Problem: POI hitting 20" low @ 1000

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: doc76251</div><div class="ubbcode-body">What your describing is the classic difference between IPHY and MOA in the scope knobs. Calibrate your scope.

Cheers,

Doc </div></div>

Sorry Doc. I understand the diff between IPHY and MOA but I don't understand what you mean by "Calibrate your scope".

Alan

 

[doc76251]

Re: Problem: POI hitting 20" low @ 1000

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GSSP</div><div class="ubbcode-body"> Sorry Doc. I understand the diff between IPHY and MOA but I don't understand what you mean by "Calibrate your scope".

Alan </div></div>

Have you checked to see if your knobs are actually giving you MOA click values. Loopys are notorious for advertising MOA but in reality they give you IPHY.

Quick test.

Lock the gun (or scope) down at 100 yards so it cant move when you dial the scope knobs, (ratchet straps or a vice work good for this). dial up 10 "MOA". If the reticle moves 10" it's IPHY if it moves 10.5 (10.47") it's in MOA.

If you find that your scope dials OTHER THAN 10.47" at 100 yards you need to run your ballistics data through a modifier to account for your knobs.

Lindy has an article on "how to calibrate your optic" on his web site.
http://www.arcanamavens.com/LBSFiles/Shooting/Downloads/ScopeChecking/

Cheers,

Doc

 

[Alan Griffith]

Re: Problem: POI hitting 20" low @ 1000

Doc,

Ah, that! Yes, I have heard of that but didn't think to verify a Nightforce's calibration. Well, it's 0508 hrs and am about to head out to verify my 100 then 1000 yd POI's. I'll let ya know my results.

Alan

 

[gstaylorg]

Re: Problem: POI hitting 20" low @ 1000

FWIW - depending on which you have, NF reticles/turrets are calibrated in either true milliradians or true MOA (not IPHY).

 

[doc76251]

Re: Problem: POI hitting 20" low @ 1000

I must have missed the NF part of the thread. Yes NF is VERY consistent in their turrets, that being said I have run across a (very) few. Worth a check just for the piece of mind.

Cheers,

Doc