Do I have a scope tracking issue?

pjohnson8168

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Ok, have a good load worked up for a new Seekins 6.5 Creedmoor, shoots 0.6 - 0.8 MOA regularly with a muzzle velocity of 2815 fbs. Using a few different ballistic apps, all were in agreement that with 130gr ELDM I should have a 9.4 MOA come-up at 500yds with a 2040 fps impact velocity.

Today was its trial run at 500yds, the good news is that group size ranged from 0.8 - 1.0 MOA at 500yds, its been months since I have shot at that range so I was reasonably happy, another piece of good news is that my impact velocity was spot on (our range has a chrono at the 500yd target).

The puzzling thing is that dialing 9.5 MOA put me a full MOA high (5"+), I dialed back down to 8.5 MOA and that put me where I need to be. Now I can "tune" the apps a bit and make reasonable adjustments to for .1-.3 MOA change but a full MOA would be huge changes to velocity, bullet BC, etc that just doesnt make sense.

I am left wondering about my scope, its a Zeiss V4 4-16x44, havent shot this paticular scope at distance before this, it was purchased as demo from Red Hawk

Is my scope where I should be looking or am I missing something obvious (which I seem to do frequently).
 

PredatorSlayer

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Could be your scope. What are you shooting off of? Bipod? Bags? If your Barrel is making contact with the stock, that could cause a shift like that.
 

Hunter609

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I have the same scope bought as a redhawk demo and had the same issue at 600 yards I was 2 moa less then it should have been
 

sndmn11

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I have the same scope bought as a redhawk demo and had the same issue at 600 yards I was 2 moa less then it should have been

I am left wondering about my scope, its a Zeiss V4 4-16x44, havent shot this paticular scope at distance before this, it was purchased as demo from Red Hawk

Have either of you don't a tall target test at 100 yards?
 

XLR

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Have either of you don't a tall target test at 100 yards?
This is the answer to your questions! If you don't start at square 1 for tracking then you end up chasing your tail! Start with a tall target test and see where you end up! Then if it is tracking good, change that BC! If it isn't tracking good then at least you have a solid confirmation!
 
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pjohnson8168

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Thanks guys, I should have done this test before bringing it to Rokslide! I will give it a go this weekend and report back.
 
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hamilton1223

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I think another thing that gets over looked is having a perfect zero, or adjusting for the offset in your ballistic solver. If your gun is shooting .8 MOA, I would make sure and shoot at least 5 shots for a good zero. It could be that when you zeroed, your gun's natural variance over 3 shots or whatever was just .6 or so low or high that day. If it isn't compensated for in your solver, then that would account for most of it.
 

XLR

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I think another thing that gets over looked is having a perfect zero, or adjusting for the offset in your ballistic solver. If your gun is shooting .8 MOA, I would make sure and shoot at least 5 shots for a good zero. It could be that when you zeroed, your gun's natural variance over 3 shots or whatever was just .6 or so low or high that day. If it isn't compensated for in your solver, then that would account for most of it.
Definitely more common than people think! IF you haven't shot a lot too, the position you are shooting in can make a change! If you are shooting on a bench you are not going to load the bipod as much as when you are laying prone! You will see a difference there especially if your barrel isn't properly free floated.

I have put a link below to a blog post I wrote a while ago but here is the short and sweet version. Once you confirm zero and velocity, and you go out to distance I like to confirm it at a few distances before changing. At 500 and 1200 if I am hitting 2 tenths (1/2 moa) high, I will knock my zero down 2 tenths and call it good. But if I am hitting 2 tenths high at 500 and 6 tenths high at 1200 then I am going to change my BC. This only works if you have a good velocity with a good chronograph! 99% of the time this is going to work out great and have great ballistic outputs for any range from 300-1400.

If you go out again and confirm your zero at 100 and stretch out to 500 and you are still 1 moa high, I would change your zero 1/2 moa - 3/4 moa and try that. If you hit 1 moa low at 100, 1/4 moa low at 300, and 1/4 moa high at 500 that will still keep you well within the bread basket! Then start working on wind calls!

Now this is all saying that your scope is tracking correct also! If it does have some error, most ballistics calculators have a way to input that and account for it! I would rather have a scope that tracks 80% every time than one that tracks between 95-100% but isnt repeatable!

 
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pjohnson8168

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Great info, thanks guys, that gives me a good set of next steps to work through.
 

Formidilosus

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Definitely more common than people think! IF you haven't shot a lot too, the position you are shooting in can make a change! If you are shooting on a bench you are not going to load the bipod as much as when you are laying prone! You will see a difference there especially if your barrel isn't properly free floated.

I have put a link below to a blog post I wrote a while ago but here is the short and sweet version. Once you confirm zero and velocity, and you go out to distance I like to confirm it at a few distances before changing. At 500 and 1200 if I am hitting 2 tenths (1/2 moa) high, I will knock my zero down 2 tenths and call it good. But if I am hitting 2 tenths high at 500 and 6 tenths high at 1200 then I am going to change my BC. This only works if you have a good velocity with a good chronograph! 99% of the time this is going to work out great and have great ballistic outputs for any range from 300-1400.

If you go out again and confirm your zero at 100 and stretch out to 500 and you are still 1 moa high, I would change your zero 1/2 moa - 3/4 moa and try that. If you hit 1 moa low at 100, 1/4 moa low at 300, and 1/4 moa high at 500 that will still keep you well within the bread basket! Then start working on wind calls!

Now this is all saying that your scope is tracking correct also! If it does have some error, most ballistics calculators have a way to input that and account for it! I would rather have a scope that tracks 80% every time than one that tracks between 95-100% but isnt repeatable!



Why would you change your zero instead of finding the error? And why are you messing with BC in the supersonic range?
 

mullmann

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Definitely do a tall target test. I have a zeiss v4 4-16x44 on a late 90’s ruger m77 mkII that started as a .30-06 and is .243 with a Schilen barrel. I have taken it to 700 yards and back and that scope has not given me any issues.
 

762 ULTRAMAGA

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Do the tall target test and see where you're at.
I've had a v4 and v6 do exactly what you're describing, and both optics failed the tracking test miserably
 

XLR

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Why would you change your zero instead of finding the error? And why are you messing with BC in the supersonic range?
So I put at the bottom to make sure that the scope is tracking correctly. The error is most likely going to be shooter error and that why changing your zero is most likely what the issue is. I ran the numbers the other day and the velocity would have to be off by around 150 FPS for it to change dope 1 moa.

I have to see that the dope is continuously getting worse over distance to change BC. If that is happening then its more than likely a BC issue (if you use a good chrono). The BC that is supplied by companies can change depending on your twist, bore size, or just from barrel to barrel. Check out the two examples above. The one I will change the zero and the other is changing the BC. I don't do both at the same time though.
 

Formidilosus

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So I put at the bottom to make sure that the scope is tracking correctly. The error is most likely going to be shooter error and that why changing your zero is most likely what the issue is. I ran the numbers the other day and the velocity would have to be off by around 150 FPS for it to change dope 1 moa.


Either the rifle is zeroed or it’s not. Building an error into the system, even if it averages out over distance, is still building an error.



I have to see that the dope is continuously getting worse over distance to change BC. If that is happening then its more than likely a BC issue (if you use a good chrono). The BC that is supplied by companies can change depending on your twist, bore size, or just from barrel to barrel. Check out the two examples above. The one I will change the zero and the other is changing the BC. I don't do both at the same time though.

Pretty hard to fake BC on decent LR bullets these days. Between 4dof, Litz, etc. I haven’t seen an error in BC that results in more than a 1/10mil out to transonic. Hundreds of rifles and dozens of different bullets a year.
 

XLR

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Pretty hard to fake BC on decent LR bullets these days. Between 4dof, Litz, etc. I haven’t seen an error in BC that results in more than a 1/10mil out to transonic. Hundreds of rifles and dozens of different bullets a year.
What is your method to trueing data if it doesn't align correctly off the factory BC and velocity you get from YOUR rifle? If you true the velocity then you are putting a fake velocity in there correct? I would love to hear your method to trueing data!
 

Formidilosus

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What is your method to trueing data if it doesn't align correctly off the factory BC and velocity you get from YOUR rifle? If you true the velocity then you are putting a fake velocity in there correct? I would love to hear your method to trueing data!

I haven’t had to correct anything above transonic in quite a while. Using a legit chrono with enough shots to get a true avg velocity and spread (20-30 shots), and using a known BC and scopes that are known to adjust to within 1% or so at 10mils results in predicted drops matching real drops. So much so, that generally I do not even chrono anymore for personel rifles- velocity calibrate at 1,340-1,350fps using enough shots (10-20’ish) and am done.
Past transonic I will adjust BC, but I prefer just to use projectiles that are stable and predictable through transonic.


The vast majority of people aren’t shooting enough rounds on a chrono to get anything resembling a true MV average, and they’re also not shooting enough rounds at distance to see the true cone show up to velocity true either. Couple that with rifles that are mechanically compromised, scopes that don’t work correctly- and you get a bunch of head scratching, weird results, and messing with BC’s, velocity, program inputs, etc.

What I have seen is when people start stacking errors upon errors such as “tracking”, changing BC, changing MV, etc. They might get the output to work in THOSE conditions, but rarely do they work in different conditions. BC changes trajectory so little in supersonic flight that you have to have a very precise way to measure it, and dudes shooting steel plates and rocks isn’t it. The best way is to figure out why the program is giving incorrect data and fix that instead of a bandaid.
 

XLR

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I haven’t had to correct anything above transonic in quite a while. Using a legit chrono with enough shots to get a true avg velocity and spread (20-30 shots), and using a known BC and scopes that are known to adjust to within 1% or so at 10mils results in predicted drops matching real drops. So much so, that generally I do not even chrono anymore for personel rifles- velocity calibrate at 1,340-1,350fps using enough shots (10-20’ish) and am done.
Past transonic I will adjust BC, but I prefer just to use projectiles that are stable and predictable through transonic.
I am sure that you have a way that works for you but it seems like there is always something that needs to be trued for data to align correct. If my ES is below 15 over 10 shots and data isn't lining up with the given BC, I am going to change BC. That is the only measurement that I do not have a hard number for. For instance on my BRA barrel I am currently running, I went out and got velocity over 10 shots and had a good zero. Shot 5 shots at 500 yards that were all .1 mil low and then went to 1200 yards and they were all .4 mils low. That is using an applied ballistics custom drag model that is provided by Kestrel. I then went in and adjusted my BC to align with what I was getting at 1200 yards and it was perfect elevation at 500, 700, 1200, and 1500. I did that in February in 30 degree temps and it was still running true this weekend at 105.

I think there's more than one way to skin a cat for sure but I am just here to share the way that I personally do things! I think that in a perfect we could use our BC off the box but with changes in twists, bore diameter, and velocity, BC is the one thing that changes from all of those so that is why I point at BC to change first. Like I said, I think there is more ways than one but we cant just expect data to align 100% of the time.
 

Formidilosus

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I am sure that you have a way that works for you but it seems like there is always something that needs to be trued for data to align correct. If my ES is below 15 over 10 shots and data isn't lining up with the given BC, I am going to change BC. That is the only measurement that I do not have a hard number for. For instance on my BRA barrel I am currently running, I went out and got velocity over 10 shots and had a good zero. Shot 5 shots at 500 yards that were all .1 mil low and then went to 1200 yards and they were all .4 mils low.

What bullet, velocity, and DA?
 

amassi

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What is your method to trueing data if it doesn't align correctly off the factory BC and velocity you get from YOUR rifle? If you true the velocity then you are putting a fake velocity in there correct? I would love to hear your method to trueing data!
Skip the factory bc as most are super inflated to sell bullets. Buy the ab app it's worth the money.

Sent from my SM-G991U using Tapatalk
 

XLR

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Skip the factory bc as most are super inflated to sell bullets. Buy the ab app it's worth the money.

Sent from my SM-G991U using Tapatalk
I completely agree! Kestrel has all the AB drag models downloaded to it!
 
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