Rifle Scopes Magnification vs mil or MOA reading?

[huntinstud101]

I am relatively new to precision shooting and I believe this is a fairly elementary topic for you guys.

I am doing my best to practice ranging with a scope but all of my estimations change when the magnification changes and I cant find the relation. I guess what I am looking for would be like 1 moa @ 10x is equal to ?moa at 15x-20x.

Thanks,

Pat

 

[Target In Sight]

Re: Magnification vs mil or MOA reading?

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=939395#Post939395

Here is your answer.

 

[Lindy]

Re: Magnification vs mil or MOA reading?

If you have a second-focal plane scope, the reticle stays the same size when you change the power.

If that is the case, there is one power at which the reticle is correct for ranging measurements. It depends on who manufactured the scope, and which one it is. You'll want to find that out. For ranging purposes, there is no reason to range with it at any other power.

If the reticle changes size when the power is changed, it's a first focal-plane scope, and it's correct for ranging at any power.

 

[huntinstud101]

Re: Magnification vs mil or MOA reading?

I guess what I am asking is wont the readings be different at 20x for holdover/windage than 10x? is it just one of those things that I have to play with to get good at?

 

[Lindy]

Re: Magnification vs mil or MOA reading?

If you're going to use a SFP scope, the easiest way is to calibrate the power ring at half power, if the reticle is accurate at the highest power. Then just cut the holds in half at the lower power.

To do that, see:

Optically Checking Rifle Scopes

Or, you could get a FFP scope, which has the same relationship between the field of view and the reticle at every power.

 

[1700fps]

Re: Magnification vs mil or MOA reading?

So i read that thread you posted, good info. Now i have a question, i hunt at night under the full moons and was curious if the reticle on an FFP would be too small or thin to see in the dark. I usually use my SFP scope on 6-12x depending what percent the moon is at and if there's snow or not. Nobody around here carries an FFP scope to compare. Other than that the FFP sounds pretty dang nice, just question low-light conditions.

 

[huntinstud101]

Re: Magnification vs mil or MOA reading?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">If you're going to use a SFP scope, the easiest way is to calibrate the power ring at half power, if the reticle is accurate at the highest power. Then just cut the holds in half at the lower power.

To do that, see:

Optically Checking Rifle Scopes

Or, you could get a FFP scope, which has the same relationship between the field of view and the reticle at every power.
</div></div>
Exactly what I was looking for sir, thanks

 

[sscoyote]

Re: Magnification vs mil or MOA reading?

In second focal plane scopes the relationship between reticle subtension and magnification is ~ inversely proportional. It's not perfect, but it's close. Several scope companies (and ballistics programs) put this 2nd focal plane reticle system to work for adjusting subtension to get a better trajectory to reticle fit. Zeiss's Rapid-Z's are the 1st to come to mind. I always use my multi-stadia reticles at the optic's highest power for rangefinding, except for a "point blank range" rangefinding system i calculate with the optic. Look here under Item C) Reticle rangefinding-- www.ottllc.com/specialtypistols/sp20.pdf

 

[huntinstud101]

Re: Magnification vs mil or MOA reading?

I get the concept of rangefinding but I wasnt sure if the ratio of mils/MOA to downrange target size changed with magnification change but I think I understand it now