I'm running a 6.5cm. My groups at 1056 yards where 1.5moa to the right. I did a tall target test at 100 yards. With 33.5 moa dialed in my groups are 1.5 moa right. I have leveled the scope to the base. Can I clock the scope left just a hair?
Rifle Scopes Tall target test and scope cant.
- Thread starter Jscb1b
- Start date
This is probably spin drift.
Your ballistic calculator should be able to predict it.
If not, there are formulas
Your ballistic calculator should be able to predict it.
If not, there are formulas
I have no idea, thinking in moa is tough for my simple brain lol.
But if I read his post right he has his scope perfectly leveled and it passed the tall target test and everything? So it has to be some sort of ballistics issue?
But if I read his post right he has his scope perfectly leveled and it passed the tall target test and everything? So it has to be some sort of ballistics issue?
I'm not sure where the Tall Target Test comes into play here, as it is a way to calibrate your elevation turret click value.
But, FWIW... I don't have your bullet or velocity info... So, I just used a 140-gr ELD-M bullet at 2737 fps (my MV) and included spin drift and plugged it (at 1056 yards) into Strelok Pro.
I got a windage value of 0.7-MOA. That's about half of what you're seeing. Of course, we are assuming zero wind, which is fairly unlikely. That's JUST from spin drift.
If I add a 1.25-mph (1-1/4 mph) wind from left to right, it brings the windage to exactly 1.5-MOA.
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When you did the test, did you have the rifle level and check the reticle against a plumb line?
The tall target test comes into play because he said at 100 yds, with 33 moa dialed, he’s 1.5moa right.
Spin drift and wind has nothing to do with it at that point.
Either the scope or reticle is canted, or as he dials up, the reticle is moving off center in erector.
Tall target tests don’t just account for the vertical movement and click values.
Also, I would probably ditch factoring in spin drift at distances where either your rifle or shooter’s ability is <= spin drift as it’s trivial at that point.
Read his post again. The 1.5-MOA group discrepancy was noted at 1,056 yards. At least that's the way I read it. If the scope is canted, the discrepancy at 1,000+ yards won't be just horizontal, right? It will also be low.
I'm familiar with the Tall Target test (and that it's conducted at 100 yards). That's why it's not clear to me what having done the test (to determine true click value) has anything to do with a horizontal (windage) offset at 1,056 yards. Generally, Tall Target tests (and corrections) are limited to elevation (though one could also calculate windage click value).
Agree with that. The scenario assumes zero wind (not likely) and a dead-on perfect hold by the shooter (also unlikely).
Ah... wait a sec... Is the OP saying that when he dialed 33.5-MOA for the TALL TARGET TEST, the 2nd group was 1.5-MOA off horizontally (on the tall target)???
Aha! Sorry.... perhaps I misread the OP. Yeah... at 100 yards, spin drift ain't got nothin' to do with it, eh?
I suspect the rifle / scope was canted (as has been mentioned).
The Tall Target test (100 yards) and the 1,056-yard comment make the post confusing.
Aha! Sorry.... perhaps I misread the OP. Yeah... at 100 yards, spin drift ain't got nothin' to do with it, eh?
I suspect the rifle / scope was canted (as has been mentioned).
The Tall Target test (100 yards) and the 1,056-yard comment make the post confusing.
Ah... wait a sec... Is the OP saying that when he dialed 33.5-MOA for the TALL TARGET TEST, the 2nd group was 1.5-MOA off horizontally???
Aha! Sorry.... perhaps I misread the OP. Yeah... at 100 yards, spin drift ain't got nothin' to do with it, eh?
I suspect the rifle / scope was canted (as has been mentioned).
The Tall Target test (100 yards) and the 1,056-yard comment make the post confusing.
He saying it was off at both distances.
Thanks everyone. I'm shooting hornady 140gn OTBT at 2650mv. I used the berger ballistic app to figure out 33.5 moa up. I had to add 1.5 moa left to be on target at 1056 yards. There was no wind. Flagging tape at the bench and target where still. I set up a 4' tall cardboard box at 100 yards. I then used a level to draw a line on the box. I rezored my scope and shot a 5 shot group at a dot 6" from the bottom of the box. I then added 33.5 moa to the scope and shot at the same dot. My 5 shot group was 34" up and 1.5 " to the right. The group should have been right on the line. Right?
Thanks for clarifying. I'm not nearly as seasoned as most here (so I hesitate to chime in), but I've been diving deep into the knowledge base. Yes... the top group (33.5-MOA added) should also be centered on the vertical line drawn on the Tall Target. Got a pic of it?
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What are you and the rifle capable of? Are your groups well under an moa when shooting? If so and:
If the rifle (and you) aren’t canted while you’re shooting then you have a few options:
If its repeatable, either find out where the reticle starts moving and adjust for it, or rotate the scope slightly (and see if it tracks properly every 5 moa or so).
Or, if it’s outside of what the manufacturer considers acceptable, send it back for warranty work.
If the rifle (and you) aren’t canted while you’re shooting then you have a few options:
If its repeatable, either find out where the reticle starts moving and adjust for it, or rotate the scope slightly (and see if it tracks properly every 5 moa or so).
Or, if it’s outside of what the manufacturer considers acceptable, send it back for warranty work.
I used two carpenters line levels to level the rifle and scope base. I then leveled the brake to the base. I installed the scope and leveled it to the brake. I used the top of the elevation turret to mount the level.
Well... I don't know if you can do much better than that! Any chance it moved? Confirm with levels now?
If that checks out... perhaps it's a scope problem as was mentioned earlier. What kind of scope?
If he’s using a level mounted to the optic and it’s level to the reticle, rifle doesn’t matter.
This is why problems like this are difficult to diagnose without either being there or asking a lot of questions.
Yes... I was referring to the scope being level with the rifle, earlier. Your description of your scope mounting process sounds like it should be good. My point was that if it moved or somehow was not level with the rifle... when you lined up the reticle with the plumb-line / vertical line on the Tall Test Target, then the rifle might be canted (relative to the scope). Hope that made sense.
Gonna simplify this so I can make sure I get it:
OP shot at 1056 yds and was vertically on target but 1.5 MOA to the right. No wind. Dialed in the correction and shot at 100 yards ( tall target style) and even after he dialed in the correction horizontal he was again 1.5moa off to the right?
If this is correct let us know....not worried about verticle since it sounds like it's pretty good or right about where it should be. It's the horizontal that is the concern even after the correction is made.
Stupid question but did you correct for closer parralx etc? Were you squared to both targets or off to the side slightly?
OP shot at 1056 yds and was vertically on target but 1.5 MOA to the right. No wind. Dialed in the correction and shot at 100 yards ( tall target style) and even after he dialed in the correction horizontal he was again 1.5moa off to the right?
If this is correct let us know....not worried about verticle since it sounds like it's pretty good or right about where it should be. It's the horizontal that is the concern even after the correction is made.
Stupid question but did you correct for closer parralx etc? Were you squared to both targets or off to the side slightly?
My max is 54.25moa. So if I get a 4x8 sheet of ply wood and shoot my target, with max moa I should be roughly 2.5 right? If everything checks out for level this would mean the erector is not centered and pulling right. Correct?
54.25 total?
Here is a sanity check to try....if 33.5 gets you that 1.5 deviation, try 16.75 elevation and see if you get 0.75 deviation? If no deviation then add half more...8.5ish and see if any deviation occurs....basically let's see if it's proportional or if there is a breaking point where it suddenly begins deveating
Here is a sanity check to try....if 33.5 gets you that 1.5 deviation, try 16.75 elevation and see if you get 0.75 deviation? If no deviation then add half more...8.5ish and see if any deviation occurs....basically let's see if it's proportional or if there is a breaking point where it suddenly begins deveating
Dean, typically it’s very difficult to notice spindrift until shooting beyond 500 yds. If your tall test at 100 yds shows 1-1/2 moa Rt with 1000 yd dope on, but is centered with 100 yd dope, it sounds like a canted reticle with respect to tracking or something similar
I went out today with a 4x8 sheet of plywood. I set it at 100yrds. I drew horizontal and vertical lines on the plywood. I then checked my zero with a three shot group, good. I then added 12 moa and shot 3 rounds, on the line. 12 more moa 3 shots, on the line. 12 more moa 3 shots, on the line. 12 more for a total of 48 moa 3 shots, on the line. I think having the horizontal line showed I was canting the rifle. Thank for the help everybody!
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