Scope adjustments - MOA explanation at different ranges

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Scope adjustments - MOA explanation at different ranges

Post by mightus » 03 Jan 2022, 8:41 pm

Hi peeps,

I got into shooting last year and ive spent a decent amount of time at the range shooting but always want to learn more from the experienced folks.
Its a great community and ive met some great lads in conversation at the range. Got myself a .22, .223, 12g and a .308 now.

Can someone help me understand better MOA adjustments? I get that at 100m using 1/4 click scope adjustments 4 clicks will be 1 MOA = 1inch
and at 200m 1 MOA = 2inchs

In regards to my .22LR setup. i zero at 50m, what adjustments (how many clicks) to adjust up for 75m and 100m?

How do people ascertain what adjustments are needed exactly without getting it on paper at distances eg. 100 to 150m, 100 to 200m, 100 to 250m. Is there a simple maths to it?
Or is just simply just shoot, adjust sights and test.

For hunting purposes i know i can zero at 100m slightly higher (eg. 1.5inches) to be 'on' at 200m and slightly low at 300m.

Considering doing a marksmanship course just to understand it all better instead of just slinging rounds down range.

Sorry for the long post.

Thanks in advance
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Re: Scope adjustments - MOA explanation at different ranges

Post by GQshayne » 04 Jan 2022, 7:30 pm

If I understand you correctly, you are confusing yourself unnecessarily. MOA is mostly used to quantify accuracy. Sighting in for a certain range, holdover etc is a different matter in my view. Each rifle, with individual loads will be different. So you will need to work that out for yourself.

The exception is that some scopes can be bought pre-set with BDC reticles for certain calibres. I think .223 is a common application of this. Leupold offer a service where you work out your ballistics and then they custom make some turret caps for you. I am not interested in this stuff myself, so my info may be a bit dodgy. Check it out for yourself.
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Re: Scope adjustments - MOA explanation at different ranges

Post by bladeracer » 04 Jan 2022, 8:05 pm

One minute is simply one-sixtieth of one-degree.
At 100m it's 29.07mm, so 200m it's 58.14mm, at 50m it's 14.54mm, and so on.

You will need to confirm precisely what your scope adjustment is, whether it truly is quarter-minute clicks or rounded to one-inch at 100yd.

How many clicks will depend on the ballistics of the ammo you are using, all ammo is different. You will still need to confirm by actually firing at each distance.

Use a ballistic calculator to roughly calculate your trajectory, then confirm it through actual shooting.

With CCI Standard Velocity I use a BC of .165 out to 300m or a bit further, and my shooting follows it very closely. High-Velocity Federal F510 I'm using .135 I think, but I need to do a lot more shooting to finalize the BC.

Basically, you need to get out and do lots of shooting at different distances, and keep lots of notes.

You also need to test lots of ammo to determine which shoots best in the rifle.


mightus wrote:Hi peeps,

I got into shooting last year and ive spent a decent amount of time at the range shooting but always want to learn more from the experienced folks.
Its a great community and ive met some great lads in conversation at the range. Got myself a .22, .223, 12g and a .308 now.

Can someone help me understand better MOA adjustments? I get that at 100m using 1/4 click scope adjustments 4 clicks will be 1 MOA = 1inch
and at 200m 1 MOA = 2inchs

In regards to my .22LR setup. i zero at 50m, what adjustments (how many clicks) to adjust up for 75m and 100m?

How do people ascertain what adjustments are needed exactly without getting it on paper at distances eg. 100 to 150m, 100 to 200m, 100 to 250m. Is there a simple maths to it?
Or is just simply just shoot, adjust sights and test.

For hunting purposes i know i can zero at 100m slightly higher (eg. 1.5inches) to be 'on' at 200m and slightly low at 300m.

Considering doing a marksmanship course just to understand it all better instead of just slinging rounds down range.

Sorry for the long post.

Thanks in advance
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Re: Scope adjustments - MOA explanation at different ranges

Post by animalpest » 04 Jan 2022, 9:28 pm

MOA can be used when adjusting scopes for the drop at various ranges. For example one of my rifles has a drop for the bullet of 40 inches at 500 yards. Adjusting the scope up 8 MOA (ie 8"at 100 yds) and I am on target at 500.

For normal shooting ranges 1 MOA equals 1 inch at 100 yards. (Close enough).

You need to work out the drop at different ranges and then calculate that back to MOA adjustments.
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Re: Scope adjustments - MOA explanation at different ranges

Post by Larry » 05 Jan 2022, 10:41 am

There are maths to the drop rate of the bullet and MOA is the common unit used for the scope offset adjustment. There are many ballistic programs available online some can be downloaded to your phone. Personally I like JBM and use it online it has nearly all the calibers and different bullets in its library. Then it just comes down to knowing your muzzel velocity as that is an important input. It will spit out the drops for any distance you want from a particular zeroed range it is accurate to within 1/4 moa over long distances.. www.jbm.com
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Re: Scope adjustments - MOA explanation at different ranges

Post by bladeracer » 05 Jan 2022, 12:45 pm

Something to remember about minutes is that there is no fixed size, a minute is a different size depending on distance. You can look at an object in the distance and estimate its size reasonably accurately. That goat is about two-foot-six at the shoulder, that Coke can is about 150mm tall, that fence post is about as wide as my hand, and so on, its distance is irrelevant. But you can't do the same with minutes unless you know the distance. Even through binoculars you have a rough idea of the size of things, whether they a meter away or a thousand meters away.

Optics generally give you some sort of scale that relates the view to the distance, based on the magnification. If your scope has a reticle that is .25MoA thick at 18-power, you can use that to approximately measure things, without knowing the distance. That fence post is about four reticles wide, so it's a minute wide. If you know the distance then you can calculate the actual width. If you know the distance is 400m, then you know the post is about 120mm wide. Likewise, if you set up a 200mm gong in a paddock, you can compare its size to your reticle. If the gong is about six reticles wide, or 1.5-minutes, you can calculate that the distance is about 460m. Scopes nowadays have additional stadia in the reticle to make this easier. Binoculars don't have any reticle, but if you know how wide the field-of-view is, you can use that to approximately sizes and distances. My 7x50's for example have a FoV of 15.7m at 100m, so if I see a large deer I can roughly tell the range by comparing its size to the FoV. Our eye can generally bisect a circle fairly accurately, so you only need compare your target to the distance from the centre of the view to the edge, or about 7.85m@100m. If you are looking at a deer that you figure is about two-meters wide, and it covers about a quarter of your half-view, you know it's about 400m away.

With a second-focal-plane scope you can further complicate the above by using your zoom to change your reticle dimensions. Your reticle dimensions will be twice as big at half the zoom, four-times at a quarter zoom, and so on.

Understanding how minutes relate to dimensions is certainly important. But if you are shooting at a target, and your bullets are hitting some distance to the left in your scope, you don't need to know the distance or the size. You only need to estimate how many minutes you are off, and adjust by that many minutes - the distance is irrelevant. My reticle is a duplex with bullet drop stadia. The duplex reticle is 3MoA radius, and I can use that to very quickly estimate how far I missed by, or how much wind I need to allow for.

Likewise with my BDC holdovers, which are at 1.7, 4.4, 7.6, 11.4, and 15.4MoA (top of the duplex) vertically below the reticle (all my scopes are the same so I have memorised these five numbers by now). These are supposed to follow a "standard" 55gn .223 load, but don't, at least not for precise shooting.

Relating this back to what I mentioned earlier, if I need to holdover 30-minutes, my reticle only measures to 15.4-minutes, so I can try to hold twice as far down the post...or I can wind the zoom back to 9-power and my reticle magically transforms to a 30.8MoA holdover.

Other scopes use grids or dots at minute or millirad intervals.

It all sounds immensely complex, but once you spend some time playing with it it will become second nature.

Try shooting a scope box test to get a feel for it. Set up a decently large target page, say two A3 pages at 50m. Zero your rifle to an aiming mark in the centre - and reset your turrets to zero, or note your turret positions. Then wind your scope up 10-minutes (40 clicks) and right 10-minutes. Shoot a group while holding the same aim point in the centre of the page. Then go 20-minutes down and 20-minutes left. Shoot another group. Then come up 20-minutes and shoot a group. Then 20-minutes down and right, shoot a group. Then up and left 10-minutes. Your final group should be dead on the centre again, if the turrets track accurately. The other four groups should be 145mm vertically and horizontally (not diagonally) from your centre group if the turrets are true quarter-minute clicks.

Remember, the "up" and "rt" on the turrets refer to the direction you want your bullets to move across the paper, not the direction the reticle moves. If your group is to the right of your point of aim, you want your bullets to "move" to the left, so you turn the turret "left". When your zero the rifle you want to shoot a group, then hold the rifle still and adjust the turrets to move the reticle to your group, in this case you will turn the turrets in the opposite direction to their markings.
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