Rifle Scopes Scope tracking and a zero question

[jasonk]

I know that the next range trip will answer this for me, but I have to ask.

I have a 200 yard zero that I feel pretty good about, then I shot to 300....no real surprises. Then, the next range trip I dial my scope back to 0 mil, I shot at 100 to put some rounds over the chrony and a nice tight group exactly 2.5 inches above zero. Then, I get home, run some charts on the computer and the Ipod w/ Ballistic, they both show I should have been much closer to 1.5" above zero....so a whole inch high??

Question is, being a whole inch higher than I'd expect, did my scope bite the big one and not track back down from the last time I used it at 300? The charts say no not really, not exactly the same as if it didn't track back down, but it's definitely shooting high for 100 yards with a 200 yard zero. Does that make sense?

Also...one more factor...I shot the 200 yard zero from prone and the 100 yard group off the bench. Now I've heard that different cheek welds, etc can cause a slight zero shift, but a whole inch at only 100 yards??

So...anyone experience this as well or is my scope toast?

For anyone wanting to run the numbers:
2820fps, 338 300gr smk (.768 BC), 250 ft abv sea level, 338 norma.

 

[deadly0311]

Re: Scope tracking and a zero question

jason your scope is toast, you know my address ill put it to rest for you. But it probably has a few variables in there that could have thrown the group high. Positional change probably isnt it, could be different atmosphere conditions, or could have been a slight powder variation. But most likely your scope is toast, send it to me

you might try and get a 100 yd zero and run a 10 mil box test at 100

 

[Lindy]

Re: Scope tracking and a zero question

What's the sight height above the bore?

 

[LoneWolfUSMC]

Re: Scope tracking and a zero question

Ok, if I understand this right, you never actually recorded a 100 yard dope? You were just comparing the actual impact to an estimated dope?

If that's so, then don't worry about it. Just note it and drive on.

 

[jasonk]

Re: Scope tracking and a zero question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">What's the sight height above the bore?
</div></div>

Badger 1" USMC rings on a Premier 5-25, quick measurement had me at 1.8-1.9" or so...I played with this number some +/- and it didn't sway the results that much at only 100 yards.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LoneWolfUSMC</div><div class="ubbcode-body">Ok, if I understand this right, you never actually recorded a 100 yard dope? You were just comparing the actual impact to an estimated dope?

If that's so, then don't worry about it. Just note it and drive on.</div></div>

Normally I would agree with you, if it was 500 yards I wouldn't be asking the question, I've just seen the programs work very well in the past and 1" at 100 yards is a fair distance to be off when I know all the other input is good.

Anyway, appreciate the ideas, Deadly it's not headed your way though.

 

[LoneWolfUSMC]

Re: Scope tracking and a zero question

Run a tracking test on it at 100 yards.

If it tracks true and returns to zero, then you need to look at what data you are inputting for your ballistic programs.

 

[jasonk]

Re: Scope tracking and a zero question

I know the test will answer all, as mentioned in the first post, was just curious of others experiences on predicted vs actual zeros.

I'm also curious, again just for thought, could you run a 5 or 10mil tracking test.with a smaller piece of paper using you mil dots or hashes as aiming points? Example, click up one mil, hold the first mil/hash on bullseye, should hit dead center? Repeat as many times as you have hold unders for? I'll experiment when I do mine.

 

[deadly0311]

Re: Scope tracking and a zero question

yeah you could do a 5 mil test get a zero at 100, then dial 1 mil and hold the reticle dead center of your zero, and repeat in all directions. But i still think its toast, so you can box it up and send it to me so you dont have to deal with it. you get to your destination for the hunt?

 

[Lowlight]

Re: Scope tracking and a zero question

I actually did a video with the SWFA Super Sniper before leaving TX and show how you can do, what i am calling a Right Angle Tracking test with a Mil / Mil scope.

I dont' measure, I just place the tracking targets at a right angle using the aimpoint at the low left corner of the triangle. Then I randomly place the points up on an angle, without measuring so I can "read' the reticle and see how it works. Pretty successful so far, and have it on video for the SS review.

 

[jasonk]

Re: Scope tracking and a zero question

So upload the video!!

Okay, I'll tinker with it some and see how it works.

 

[sobrbiker883]

Re: Scope tracking and a zero question

Lots of loads I've shot would run with my data from a 100yd zero well at 400 and 500 (projected matching field), but be different at 200-300 than what the ballistic calcs I use (PSSF and JBM) say they should be.
I like to use the "on target" program. I hang a big target with aiming points for 200, 300, 500 and zero at 100, then shoot groups at the big target using my phone program. Then I pull the target and use the "on target" program to measure the groups variance vertically from my POA and adjust my field dope accordingly. Often I'm then successful in tweaking my phone's program to match reality.