I may show my ignorance here in not know what is going on, but a buddy and I each have 7 mm rem mags. Mine is a savage, his a remington. Dialed in windage on both at 100 yards and shooting at 600 yards with both, we see 8 inches of drift to the right that we cannot account for. It was not wind related. Anybody know what is going on?
- Thread starter uppercut11
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What do you mean by can’t account for it? What all factors are you accounting for because it sounds close but a little high for spin drift.
What indicators did you use to estimate that the wind speed or direction at the target was in fact the same at the firing point if that's where you measured it? It's fairly common to make wind call errors, either under or overestimating speed and value.
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So you’re off 0.4 mils right. Hold 0.4 mils left. To quote Frank: “Use the ruler 3” in front of your nose.”
Thanks for the quick responses. Sorry I hadn't provided enough detail. We measured wind with a wind gage at multiple points between us and the target. Used ballistic calculator for our specific loads (BC, velocity, etc.) to calculate wind drift. In both of our cases, there was about 8" of drift to the right more than could be explained by the wind.
Spin drift is really what I am wondering about that I am not very familiar with. How much drift do you get and how do you account for it? Would it be enough to explain what we are seeing?
Spin drift is really what I am wondering about that I am not very familiar with. How much drift do you get and how do you account for it? Would it be enough to explain what we are seeing?
any video of your shooting not the target or impacts but of you squeezing the trigger ,and do you squeeze the gun when you shoot white knuckle it . Is it only at 100 yards and 600 yards ? 200 - 500 are normal that would be neat .are you consecutively shooting heating the barrel or pausing to let it cool down ?
You hit on exactly what I was wondering about. I should have written the original post better.
Is the gun level? Is the reticle plumb over the bore? If you are tilted to the right it will easily move the point of impact that far. That said wind calls are as much art as science. YMMV
There is a formula for spindrift, think Litz has it in his book but I’d have to look. The ballistic software you used should calculate it but you’ll have to tell it which way your barrel twists and the rate then some have another option you’ll need to turn on/off to have it account for it. 8” I think would be high at 600, usually it’s between about .25 and .6 MOA...I think.
No video unfortunately but two shooters seeing the same thing consistently with 2 different guns. I know that doesn't rule out the problem being trigger pull but makes it less likely. The shots were from a lead sled. Very light hold on the gun. I had an uncle growing up that drilled me on practicing trigger pull so I feel pretty confident I am good there. That day we just shot 100 and 600 as that is the range we had available and were confirming bullet drop was what we expected. We did shoot a few consecutive shots but never let the barrel get hot enough that you could not comfortable grab and hold it.
We both have scope levels and verified level on each shot. I believe the reticle is plumb over the bore but I guess I don't know how to check that or how you would adjust if it wasn't.
I have just used free ballistic calculators I can find online like http://www.shooterscalculator.com/ballistic-trajectory-chart.php and haven't seen that option that I can find. I used to use one from handloader.com but can't seem to find that one anymore. Is there one you know of that I should try or would that be more in programs that you buy? Someone told me that I should just dial in the windage at about 600 yards and then it will be close enough at any hunting yardage at least, but I really like to understand what I am seeing and be able to properly account for it.
Did not assume wind drift would be the same. Measured wind and used ballistic calculator to calculate drift at 600 yards. Wind accounted for 10" of my 18" of drift and 12" of his 20" of drift (different bullets and velocities).
Like others said, you’re not seeing 0.4mils of SD at 600 yards. Probably a combination of bad wind call, poor fundamentals, a little cant, itty bitty SD.
Are you guys right handed or left handed shooters?
Are you guys right handed or left handed shooters?
It’s definitely wind, a slight cant, or something along those lines. I’ve measured spin drift + coriolis effects at distance many times, and it’s different for each bullet, but in general at 1000 yd you won’t see more than .2 mil TOTAL drift to the right not due to wind. Most of my 6mms end up right at about .15. At 600 it’s ~.1. A big 7mm or 30 cal might have more, but not to the degree you’re seeing. .15 at 600 max. So the other .25 drift, which is not much, could easily just be from a .5-1 mph wind you can’t see or feel, or from a tiny bit of rifle / scope cant.
Others here are better at fault diagnosing your lateral error, but in the subject is spin drift and ballistic calculators, look at Hornday’s 4DOF. Its available free online on their site and they have a free app for your phone.
Wind+cant+spin drift+not a perfect zero+shooter error
A combination of some or all of that. Many times it’s not just one thing which is why people scratch their heads because no single thing equals the total error.
A combination of some or all of that. Many times it’s not just one thing which is why people scratch their heads because no single thing equals the total error.
Thanks. I have played with that one some but didn't see the spin drift in there. I will check it out again.
Unless you’re running lidar, you will almost never be able to account for all wind
Just tried to use that one but it makes you choose a specific bullet and doesn't have my 160 gr Nosler Accubond as an option so I can't use for my load. Is there a way to enter custom information that I am missing?
Agreed. I certainly could have been off a bit on the wind. It just seemed weird to be off 8 inches consistently on multiple days in the same direction.
Ah, yes...it requires a drag curve determined by Hornday via testing and if the bullet isn’t in their tested library yet, you can’t use it.
And yes, their BC calc does not provide spin drift. Sorry for the miss direct.
No worries. I appreciate it anyway. It was worth a shot and you had no way to know what bullet I was using.
Was reading this thread https://www.snipershide.com/shootin...rift happens at all,1mil around 500-600 yards. General conclusion seems to be to ignore spin drift entirely. Any thoughts?
Most people can’t shoot the difference or call wind close enough. Spin drift is less than the error already built in from shooter and wind. At least at 1k ish and closer distances.
So you had gauges (plural) along the trajectory (at the proper height) and recorded speed and direction, plotted the results and synced timline to the bullet’s flight, and integrated your wind solution?
Don’t take this the wrong way - it’s rhetorical. Everyone here uses wind gauges. We all still miss due to bad wind calls here and there.
I align the reticle with gravity.
This past week, Modern Day Sniper aired a full week of interviews with industry luminaries including our own @lowlight
Aside from Frank, the three I liked the most was Ted who owns American Rifle Company, can't remember his name from Leupold but he provided excellent technical education on aspects of scopes, and Jayden (I think) who is a Hornday ballistician who talked extensively about 4DOF, its use of a true artillery type ballistics engine, and that there are something like 450 data points in a bullet library file to define the drag curve (not coefficient, but the curve going to distance).
Of course, first bullets that they do are theirs and we will see how fast they get more curves in the library for other manf. They do seem to have a pretty good (though I don't think complete) library of Berger, Lapua, and Sierra but wow, they are indeed short on the Nosler.
Applied Ballistics also has a calc that uses empirically derived drag curves, has a library of bullets but not sure how extensive as I have not used it myself, but its also not free though compared to what else we spend on this sport, its not too painful, perhaps.
AB Tactical App
store.appliedballisticsllc.com
I don't think he was asking how to level a scope but rather someone speculated that a possible source of the error is that his scope is not longitudinally aligned with the bore....that is, either his mount, rings, or scope...or all three...are a bit cockeyed.
This does seem to be a very reasonable view of the OPs issue:
I agree with you completely that we could have miscalled the wind somewhat. We did take readings at a few points along the way to the target a few different time but no doubt there was some error there. Just seemed odd that on multiple days in different conditions it ended up 8" right each time. I was wondering if it was spin drift, but that seems unlikely to have accounted for more than an inch or two from what I am reading. I don't claim to be the best shot out there but from a leadsled and shooting bench I feel like I am pretty consistent. The groups were around 0.75 MOA from what I recall.
Thanks again. I am looking at another gun soon and have been wanting to try the ELD-X bullets for a while so it should come in handy when I get to that!This past week, Modern Day Sniper aired a full week of interviews with industry luminaries including our own @lowlight
Aside from Frank, the three I liked the most was Ted who owns American Rifle Company, can't remember his name from Leupold but he provided excellent technical education on aspects of scopes, and Jayden (I think) who is a Hornday ballistician who talked extensively about 4DOF, its use of a true artillery type ballistics engine, and that there are something like 450 data points in a bullet library file to define the drag curve (not coefficient, but the curve going to distance).
Of course, first bullets that they do are theirs and we will see how fast they get more curves in the library for other manf. They do seem to have a pretty good (though I don't think complete) library of Berger, Lapua, and Sierra but wow, they are indeed short on the Nosler.
Applied Ballistics also has a calc that uses empirically derived drag curves, has a library of bullets but not sure how extensive as I have not used it myself, but its also not free though compared to what else we spend on this sport, its not too painful, perhaps.
AB Tactical App
store.appliedballisticsllc.com
That was my question exactly. I have one piece DNZ bases / rings. I have never heard of issues with the scope not being centered over the bore. I certainly see that you would have issues if it was not centered, but I don't know how you would A) check that alignment, and B) correct it if it were off.
Thanks. That makes sense. I agree that number 2 sounds easier. Would be difficult to measure precisely enough I think with method 1 to see a minute difference. Shooting also sounds more fun than measuring!
How are you verifying velocity?
Nosler Accubond were (not sure if this is still the case) way off on their published BCs. How have you verified the BC?
Does this just show up as 8” @600, or do you see different results than expected/calculated at 400 and 500?
I would quit looking at spin drift as a suspect.
Nosler Accubond were (not sure if this is still the case) way off on their published BCs. How have you verified the BC?
Does this just show up as 8” @600, or do you see different results than expected/calculated at 400 and 500?
I would quit looking at spin drift as a suspect.
would be interesting to hear the results of the 300m shoot, and if the point of impact is out by 1/2 of the 600m shot.
@Baron23 & @uppercut11
www.snipershide.com
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Gunsmithing - Scope level to a rifle
I have a Precision Extended Cantilever mount (1 piece) and I'd like to install it on AR10 - DB10 but I have a problem. I can't mount a scope leveled to a rifle properly (without cant). Do you have solution for it? I have an Arisaka Optics Mount Tool but it won't works for me - surface on mount...
www.snipershide.com
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Are the rifles being zeroed at 100 then being shot at 600 the same day?
Have you shot it outside of the lead sled to see what happens??
I've seen rifles do weird shit in a lead sled. But never gave them the time of day to figure out if it was user error or what. I just knew my rifle shot a hell of a lot better when it wasnt in that thing.
Have you shot it outside of the lead sled to see what happens??
I've seen rifles do weird shit in a lead sled. But never gave them the time of day to figure out if it was user error or what. I just knew my rifle shot a hell of a lot better when it wasnt in that thing.
It is mainly spin drift. That is approximately a half minute at 600 so that accounts for about half. The rest could be changing conditions OR your scope is not plumb and giving you some windage as you dial in elevation. Check your scope for vertical with a plumb bob at 100 or better further out. Report back the results.
A, yeah....but what’s that got to do w the price of TW in China?@Baron23 & @uppercut11
Gunsmithing - Scope level to a rifle
I have a Precision Extended Cantilever mount (1 piece) and I'd like to install it on AR10 - DB10 but I have a problem. I can't mount a scope leveled to a rifle properly (without cant). Do you have solution for it? I have an Arisaka Optics Mount Tool but it won't works for me - surface on mount...
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What? I linked some info for you two as it seems neither of you are able to run the numbers to determine how important (or unimportant) it is to have the cross hairs lined up with the center of bore. I also provided a white paper that goes over cant.
As I said in my original response, this islikely a combination of several errors - most of which point back to the shooter. The sooner dudes stop blaming SD, AJ, coriolis, SD/ES, harmonics, etc, etc. and start recognizing that they as a shooter are the majority of the problem, the better they will become.
Doubt it’s spin drift as that wouldn’t be that much at 600. However could account for some but not all.
It’s most likely the wind. As it would not take much change in direction or speed to cause this effect. And there’s no way to accurately measure wind across the range before shooting and rely on that for the duration of the session.
Wind constantly changes. That’s why having experience reading it is so important. Wind flags help a lot if your range has them out.
I’d expect even your ballistic app to be off that much. I run StrelokPro and have been happy with it
However in case I’m wrong here’s a simple math equation to do before a shot that will put you right back in the game
It’s most likely the wind. As it would not take much change in direction or speed to cause this effect. And there’s no way to accurately measure wind across the range before shooting and rely on that for the duration of the session.
Wind constantly changes. That’s why having experience reading it is so important. Wind flags help a lot if your range has them out.
I’d expect even your ballistic app to be off that much. I run StrelokPro and have been happy with it
However in case I’m wrong here’s a simple math equation to do before a shot that will put you right back in the game
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Maybe you should buy some Spin D, that will fix you right up
Yeah, but you came into the convo with “I align my reticle w gravity” after the OP was asking another member how to verify scope bore and barrel bore are aligned after that member suggested that this type of misalignment could be a source of error. Longitudinal alignment, NOT how to level a reticle.
and yeah, multiple sources of error may we’ll be in play as noted by a number of members above.
as for spin drift and Ballistic calc discussion, the OP wanted to know how to get this type of info.
hope your day gets better.
OP specifically asked me how I align my reticle. I responded that I align to gravity. To spell it out for you, the error associated with mis-aligning reticle with center of bore& having a plumb reticle is small compared to canting your optic that is perfectly aligned with the bore. Hopefully that clears up your confusion.
BTW, I get that this is the internet and that tone gets lost. But this isn’t some weird argument from my end.
Do a tall target test. Place target at 100 yards and fire three shots. Then come up 10 minutes if MOA or pick a number like 3 Mils if in Mils. Aim at original dot. Repeat but coming up additional 10 or 3 again. If you scope is tracking true you will have a plumb or true vertical impact line. If there is any deviation from plumb there is your problem. Report back on this.
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