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And if one zero's with the mechanical error to the left, spin-drift will walk it back toward center on the way downrange.

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Originally Posted by MontanaMarine
1 moa = 1.05" at 100 yards (rounded nearest 1/100th)
1/4 moa = .26" at 100 yards (rounded)

1 mil = 3.6" at 100 yards
1/10 mil equals .36" at 100 yards.

So, zeroing at 100 with 1/4 moa leaves a max mechanical error or 1/8 moa, or .13".

Zeroing at 100 with 1/10 mil leaves a max mechanical error of 1/20 mil, or .18".

That's a difference in precision of .05" at 100 yards, or .5" at 1000 yards.

That's what all the fuss is about? It's such a small difference it is irrelevant for all practical purposes. That small difference is lost in the wind, your pulse, etc.

I'm migrating to mils, because I prefer the system of tenths.



Could you please explain the max mechanical error! It seems to be 50% of the click amount and something about that seems wrong. Not disagreeing, just trying to understand.


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Well, chances are your scope clicks will not fall dead on at 100 yards. But the most you could be off is half of one click value. If it was over half value, you would go one more click, and be within a half-click value.

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Here's an example of 10 shots at 100 yards. Group is .664" wide, about 2/10 mils.

The center of the group is about 1/20 mil right of center.

I adjusted windage left 1/10 mil, putting the center of the group about 1/20th left of center, leaving spin-drift to bring bullet a little to the right.



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I didn't think there could be that much error per click! I hadn't read much about the amount of error so you forced me to do some searching. I found this

[Linked Image]

form this article http://precisionrifleblog.com/2014/08/13/tactical-scopes-mechanical-performance-part-1/

Thanks! I should have searched first! Sorry!


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I wasn't referring to mechanical error in the scope itself.

I was trying to relate the fact that the zero on paper most likely will not be EXACTLY on the aim point.


So if you are within 1/2 click value you are about as close as mechanically possible. If you adjust a click toward point of aim, you will cross center and be off on the other side more than 1/2 click value.



If you are off between 1/2 and one full click value, it would make sense to adjust one more click to be within 1/2 click value from point of aim.

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I got ya! I misread your post! Sorry!


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Originally Posted by Clarkm


Kaleb, I probably know some things about this topic that you don't.

I got a SWFA super sniper scope when Chris Farris his first picked some components from an Asian factory catalogue and imported his own brand. That was a long time after Gale McMillan did that and sold them to the marines. Any email I got from Gale was many computers ago.

I told Chris light transmission was terrible.
I have not measured it. I am not an optics engineer, but I have worked with them on attack helicopter night vision 15 years ago. I put in a lot of effort to get 120 db of dynamic range without any flicker at the bottom of night mode. I worked direct, contract, consultant, and firm fixed price contract under a statement of work. All the optics calculations were first time for me, and not a conditioned response. That was real work, doing new math.


I knew Chris from his ads in SHOTGUN NEWS and his posts on the shooter's forum in the 1990s when the WWW gun forums got started.

My father was chief engineer of a military and gun designing fortune 500 company. He mostly subcontracted the fire control [not the trigger like a Rem700 gunsmith would call it, but the aiming system] to Hughes Corp. But he did make an anti backlash split gear in an aiming system. You can't afford that in your scope nor your guitar tuning keys.


That is one tractor trailer-sized load of bullsh**.



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