When does 10 MOA of clicks really mean 11MOA,in Elites and Sightrons)

[johnsopa]

I have three Elite 4200s,one 6-24x42 and two 6-24x50). When I did my box tests on these, I was happy to see that all three scopes were very repeatable. However, I was puzzled to find that 10 MOA of clicks didn't get 10 MOA of movement -- in fact, on all three scopes I found that 10 MOA of clicks yielded 11 MOA of movement,11.5' or 10.98 MOA, to be precise).

It's a real pain to take nice trajectory charts from somewhere like JBM's website and have to convert everything by 90.9%.

Well, I figured it was just a Bushnell thing...

After reading the review on one of the newer Sightron scopes,Sightron 8-32x56 review, I'm not so sure it's just a Bushnell thing.

18 of vertical MOA should have yielded movement of 18.846' -- instead, Jason got 19.8' of movement. 15 MOA of horizontal should have yielded 15.705' of movement -- instead, the Sightron get 16.25 - 16.375'.

So, the Sightron is closer to a real MOA but still needs its elevation and windage adjusted by 95% and 96%, respectively.

These might not sound like much variation from a true MOA, but if you don't do a box test and adjust for the charateristics of your specific scope, you'd be 5' off at 500 yards with the Bushnells and 4.75' off with the Sightron.

Are these companies using a different MOA than what we use,1.047' at 100 yards) or are these manufacturing issues or ???

 

[Cheechako]

john

I don't think you're going to find any scope that has true MOA clicks. Some will be worse than others and the cost of the scope will not always be the biggest factor.

But, at the same time, no ballistic table is going to be 100% accurate either. You might find a bigger error in the table than you will find in your scope. Since ballistic tables are based on velocity, you have to add in the error inherent in your chroniograph.

Chronographs, ballistic charts, and scope clicks will get you close at the mid to long distances. If you are lucky, sometimes you'll be right on. But don't bet the farm on it.

Bottom line - you have to shoot real bullets at a real target to determine scope settings.

JMHO

Ray

 

[Preacher]

As usual Ray is spot on with his answer......... especially the real bullet at a real target part.....

 

[Fred Bohl]

johnsopa,

The following illustration shows a fairly typical internal adjustment scope configuration:

Examining the elevation adjust/turret shown, the adjustment is accomplished tilting the erector about the pivot ring near the rear of the erector tube using the turret screw and erector spring. Unfortunately, the tilt motion yields an arc curved toward the eyepiece, the image is a spherical curve inside toward the objective and the turret position is straight up and down. Therefore the actual angular aim correction,MOA) is a non-linear function of the turret position and gets worse with increasing offset from the scope axis.

To make a calibration of your turret, you will need to shoot at multiple click stops and at smaller increments as you move away from the center.

The good news is that as you go up in quality,and price) the makers have gone to some trouble to reduce or at least minimize the problem.