What is my M.O.A. per click

[Donald Neumann]

I recently acquired a Remington Arms Co. rifle scope model 24XBR with exterior micrometer adjustments sitting on top of a Savage 112 Series J with the base plates 6" center to center. The only information I was able to locate was that a spacing of 7.2" gave 1/4" M.O.A. Will I have to test fire and waste a lot of my .220 Swift ammo to estimate what my clicks are giving me or are some of you knowledgeable scope persons able to tell me what my scope clicks are giving me. I'm 82 and love rifles and optics but with this rifle and unheard of (to me) I'm needing a lot of information.

 

[ms6852]

1/4 MOA or click in your scope means that at 100 yards the reticle in your scope will move 1/4 of an inch up or down depending on direction. Below is a table that breaks it down for you and also a youtube link that explains it well. Click on the link.

 

[MEHavey]

(7.2"/6") x 0.25 MOA/click = 0.3 MOA/click

 

[Donald Neumann]

(7.2"/6") x 0.25 MOA/click = 0.3 MOA/click

Thank you!

 

[Donald Neumann]

I also have a Unertl 15X with 2" objective, one inch tube, which also was used on the same rifle with the 6" spacing of the block mounts. The Unertl is much longer than the Remington Arms 24XBR scope so would the 0.3 MOA per click still be the same, my guess it would remain the same, correct?

 

[PRD1]

I also have a Unertl 15X with 2" objective, one inch tube, which also was used on the same rifle with the 6" spacing of the block mounts. The Unertl is much longer than the Remington Arms 24XBR scope so would the 0.3 MOA per click still be the same, my guess it would remain the same, correct?

Yes. It is the spacing of the blocks for externally adjusted telescopes which determines the 'sight radius' from which the MOA values are calculated. The length of the scope tube itself does not affect these values.

PRD1 - mhb - MIke

 

[Donald Neumann]

Yes. It is the spacing of the blocks for externally adjusted telescopes which determines the 'sight radius' from which the MOA values are calculated. The length of the scope tube itself does not affect these values.

PRD1 - mhb - MIke

thank you...one more question, with the externally adjusted scope, are the incremental divisions of the turret knob (in my case 0-20) a portion of 1 m.o.a. or does it take one complete revolution to equal 1 m.o.a.....if it does these adjustments, increments, are really splitting hairs.

 

[PRD1]

thank you...one more question, with the externally adjusted scope, are the incremental divisions of the turret knob (in my case 0-20) a portion of 1 m.o.a. or does it take one complete revolution to equal 1 m.o.a.....if it does these adjustments, increments, are really splitting hairs.

The adjustments on modern external telescope mounts are true micrometers, and are read in just the same way. One graduation on the micrometer knob is equal to .001", (some mounts have intermediate clicks of half or 1/4th of that value), and one complete rotation of the knob (25 graduations on the knob or one line on the micrometer body) moves the scope tube .025" in the indicated direction. The spacing of the bases at the standard 7.2" makes the value of each .001" increment on the micrometer equal to 1MOA (or very nearly) in windage or elevation, so one complete revolution of the knob would equal 25MOA.

PRD1 - mhb - MIke

 

[Donald Neumann]

The adjustments on modern external telescope mounts are true micrometers, and are read in just the same way. One graduation on the micrometer knob is equal to .001", (some mounts have intermediate clicks of half or 1/4th of that value), and one complete rotation of the knob (25 graduations on the knob or one line on the micrometer body) moves the scope tube .025" in the indicated direction. The spacing of the bases at the standard 7.2" makes the value of each .001" increment on the micrometer equal to 1MOA (or very nearly) in windage or elevation, so one complete revolution of the knob would equal 25MOA.

PRD1 - mhb - MIke

Thanks again...that's what I needed to know.

 

[taliv]

The adjustments on modern external telescope mounts are true micrometers, and are read in just the same way. One graduation on the micrometer knob is equal to .001", (some mounts have intermediate clicks of half or 1/4th of that value), and one complete rotation of the knob (25 graduations on the knob or one line on the micrometer body) moves the scope tube .025" in the indicated direction. The spacing of the bases at the standard 7.2" makes the value of each .001" increment on the micrometer equal to 1MOA (or very nearly) in windage or elevation, so one complete revolution of the knob would equal 25MOA.

PRD1 - mhb - MIke

which scope are you talking about?

 

[PRD1]

which scope are you talking about?

All of them with external adjustment using micrometers (which is all of them, so far as I am aware), though there are/were non-micrometer (de-horned) mounts for hunting use, which were adjusted for zero and left in that condition, with the de-horned mounts being much less susceptible to inadvertent change of zero in the field. There are/were externally adjusted telescopes such as the B&L which used an entirely different adjustment system and were intended primarily for hunting use - they are excellent scopes and mounts in their own right, but do not fall into the class of target scopes under discussion.

PRD1 - mhb - MIke

 

[taliv]

then none of this makes sense to me. one graduation on the micrometer knob is equal to .001" what?

on decent scopes, graduations are measured with angular measurements like MOA or MILS, not in linear measurements like inches. and i have no idea what the spacing of the bases has to do with anything. my actions have solid picatinny rails from front to back, so what space is that?

The adjustments on modern external telescope mounts are true micrometers, and are read in just the same way. One graduation on the micrometer knob is equal to .001", (some mounts have intermediate clicks of half or 1/4th of that value), and one complete rotation of the knob (25 graduations on the knob or one line on the micrometer body) moves the scope tube .025" in the indicated direction. The spacing of the bases at the standard 7.2" makes the value of each .001" increment on the micrometer equal to 1MOA (or very nearly) in windage or elevation, so one complete revolution of the knob would equal 25MOA.

PRD1 - mhb - MIke

 

[PRD1]

then none of this makes sense to me. one graduation on the micrometer knob is equal to .001" what?

on decent scopes, graduations are measured with angular measurements like MOA or MILS, not in linear measurements like inches. and i have no idea what the spacing of the bases has to do with anything. my actions have solid picatinny rails from front to back, so what space is that?

It is a matter of geometry. Target adjustable iron sights can only give true MOA (and fractions thereof) for one specific sight radius (distance between the rear sight and the front sight), though typical target rifle installation on rifles of differing action and barrel length generally give values close enough to the nominal MOA to give little difficulty in use. Target telescopes with internal adjustment are designed by their manufacturers to give specific adjustments per click, and the internal geometry is designed accordingly, so the 'sight radius' is that of the moveable internal parts. The micrometer external mounts are graduated in thousandths of an inch, just like the precision measuring instrument of the same name, and move the scope tube by that amount per graduation: because the radius on which the scope tube moves is determined by the distance between front and rear mounts, the 7.2" distance is calculated to give the desired MOA change on the target.

In reviewing my previous comments on the MOA value of the change given by micrometer mounts, I remembered that the 7.2" scope block spacing gives 1/2MOA for each .001" graduation, and those mounts with intermediate clicks give 1/4MOA per click.

The easiest way to calculate the MOA value in inches for any given sight radius it to multiply the sight radius in inches by .00029 (the sine of 1MOA): e.g.: 7.2" x .00029 = .002088", or just over 2 thousandths of an inch.

PRD1 - mhb - MIke

 

[MEHavey]

TALIV:
High-end scopes like Unertl have fixed reticles (no adjustment), and the scope is mounted between two pivot points on front & rear scope blocks.
The rear scope pivot has a micrometer-adjustable pressure point that physically swings the scope left/right and up/down on the forward pivot -- changing aimpoint.

EXAMPLE for 0.0005" micrometer movement (1-click)

 

[taliv]

the only external adjust scope i ever really played with was the US Optics SN-9 (not my pics below) but it was in minutes (with 200min of adjustment). i honestly did not know there was one that it was an actual micrometer.

 

[Donald Neumann]

This is an externally micrometer adjuster for windage and elevation. This moves the entire scope itself not the cross hairs as they are fixed within the scope.

 

[jmr40]

Most hunting scopes are set up to move 1/4 MOA for each click. That translates into pretty close to 1/4" at 100 yards. Some are 1/2 MOA meaning close to 1/2" at 100 yards.

Most target/tactical scopes will move 1/10 MIL for each click. Roughly 1/3" at 100 yards. Some target/tactical scopes are available in both MILS or MOA. I think that most people find it easier to visualize MOA, at least initially. But once you use a scope using MILS most like it better.

If there is any other system I've not seen it.

No need to waste a lot of ammo. I've never seen a scope that wasn't marked. If not just go to a range and shoot a group at 100 yards. Move the scope adjustment 12 clicks. Shoot another group. If your group moved 4" you have MILS, if it moved 3" you have MOA.

 

[Varminterror]

@jmr40 - read the thread.