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I purchased a Springfield Armory M1A Scout squad 6+ years ago. It came with a reprint from a 1997 issue of American Rifleman that explained how to zero the sights. It was good but one thing really confuses me. I have looked for answers on the Internet but cannot find anything to answer my questions.

There is a table that shows how many clicks to move a sight that has been zeroed to 100 yards/meters for approximate zero at longer ranges. The confusing part is that for adjusting to 200 it says to go -1 click from 100 zero then for 300, use +2 from zero or +3 from the 200 yard position. I am a novice at trajectory knowledge. It is counter-intuitive to lower a sight for longer range. Then raise it for even longer range. If this was a recent article I might think the table was wrong, but it is 20 years old, its an excerpt from a book, and it is being distributed by the rifle maker. I trust it but do not understand it.

The only explanation I can think of is the initial settings they provide when setting zero at 100, 8-12 clicks up from the bottom, are pushing the initial intersection of the bullet and line of sight out to 100 from the normal 25+-. I didn’t think this was possible, but I cannot think of any other explanation.

If that is true, the second intersection, that would normally be considered “zero”, is somewhere between 200 and 300 and lowering the site pulls the second intersection back to 200. If the sight is kept at the 100 zero you would need to hold low when shooting at 200 yards and high for 300 yards!

Is this something unique to the M1A/M14/M1 rifles or the sight they use? Is it just a technique used by the writers of the book the article was taken from? I imagine it might have something to do with allowing the sight to be adjusted for longer ranges. Or am I just stupid and missing something. Could anyone please explain what is going on in this sighting process.

Thanks

REJ
 

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You are overthinking it. You can pretty much zero the sights at whatever range you normally shoot at and then calibrate the elevation drum to that tick mark. Using the drum marks from then on will keep you on paper at such ranges.

The army used 250 meters, which is the long tick mark between the 2 and 4.

Keep in mind that barrel length effects velocity. The sights are calibrated for M80 ball ammunition out of a 22" barrel.
 

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What the AMU did was crank rear sight down to bottom and click up 5 clicks and file the front sight down till it zeros at 100 yards. Bear in mind all they shot was 168 Match Kings and M118 Match ammo all loaded with 4895. Even the Fed Match they got from Federal was loaded with 4895.
Once you get the elevation right center the rear sight for windage, loosen screw on front sight and move it left or right to have it shooting center.

Now bear in mind all bets are off if you bed the rifle with down pressure on the front end.

Forgot to add if you are going to reload ball propellant has a tendency to eat barrels for breakfast. My all around match load was 40 gr. 4895 and 168 Sierra in LC Match cases.
 

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Go back i think that is using a 25 yards zero.

Dont overthink it. A 100 yards zero will get you on target at.muzzel to 200 yards. Looking it up an estimate is 100 zero will hit about 4 inches low at 200. Lots of variablels like bullet velocity etc etc

From experance a 200 yard zero will be about 2 inches high at 100

Either one will get you on steel out to 200.
 

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Go back i think that is using a 25 yards zero.

Dont overthink it. A 100 yards zero will get you on target at.muzzel to 200 yards. Looking it up an estimate is 100 zero will hit about 4 inches low at 200. Lots of variablels like bullet velocity etc etc

From experance a 200 yard zero will be about 2 inches high at 100

Either one will get you on steel out to 200.
 

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Once you have established your 100 yd. zero, the ancient method to determine "come ups" for whatever distance beyond is as follows: From 100 to 200 come up two moa(number of clicks dependent on .5moa adjustment or 1moa adjustment available from your rear sight) 200-300 three moa, 300 to 600 10moa for a total of 15 minutes from 100yd zero. If shooting at say 800yds. add another 10 moa, 800-900 add five more moa, 900-1000yds. add 5 more moa. Do not assume from these above numbers that the bullet impact will be in the 10 or X ring, but will be on the target face and can adjust as needed from there. Weather, light, etc., etc. will have an impact on the flight of the bullet and the condition of the rifle and the barrel. Disregard the numbers on the elevation drum for in early mornings or late evenings you can not see them anyway and depend on the count of the "clicks" as you adjust. Just a suggestion.
 

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Initial zero at 25 yds. Military uses 1000”, which is about 28 yds. Loosen the screw in the elevation drum, and turn the drum until the 300 yd hash mark on the drum is next to the index mark on the receiver. Tighten the screw, then turn the knob until the 100 yd mark is next to the index mark.
Now, shoot at 100 yds to fine tune the zero, and repeat with the screw and knob as needed.
 

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... The confusing part is that for adjusting to 200 it says to go -1 click from 100 zero then for 300, use +2 from zero or +3 from the 200 yard position. ...
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I have never encountered that method with an M1 or M1a - I think something is wrong there.
If you have zeroed at 100 yards, then 2 clicks UP should be good for 200 yards, and from 200 to 300 yards an additional 3 clicks UP.
 

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I agree with JayKosta. It is exactly what adjustments are required for my NM rifle, using M118 or M852 ammunition on standard NRA match rifle targets. The trouble is, you are shooting a SOCOM with a very short barrel and who knows what kind of ammunition or sight picture. These things do make a difference and not everyone's zeros will be the same. The calibration markings on the elevation pinion are set up for a 22" barrel shooting US M80 ball ammo.
 

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Yeah, 2 minutes for 100 to 200
and 3 minutes for 200 to 300.

That’ll work for starters for pretty much all the std velocity rifle ctgs along the 223/270/30 06/308 lines.
 

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Are you punching paper or going for minute of man? If you don’t want to fool with numbers or loosen the drum to set to a specific number, use the old method of marking your sights with some nail polish or model paint at your choice of distance. Remember that distance and the clicks to get up or down and be done with it. Practice. If you practice enough it will become second nature
 

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Regarding having to lower the sight for 200 yards and raise it for 300: the bullet travels in a ballistic arc. It climbs slightly after leaving the muzzle, before it begins to drop due to gravity. Your sight line is a straight line. With low mounted sights like the M14, the bullet's arc can cross the sight line as it rises, and it will then fall back below it. So at 200 yards, the bullet is above your 100 yard sight line, hence you need to lower the rear sight to be on at 200. After 200 the bullet is dropping, so you begin raising the rear sight to compensate.

As others have said, the sight was designed for M80 ball with a 22" barrel. Your shorter barrel gives you less velocity, so that can throw off calculations made for a 22" barrel. Your ammunition also affects velocity and how quickly the bullet will slow down and drop. Your best course of action is to develop your own table by shooting at known ranges and recording the number of clicks at each range.

As far as calibrating your elevation drum, I see two options.
1. Pick the most common range you shoot and calibrate the elevation drum for that so that you can quickly return to that range. So, if you most commonly shoot at 200 yards and that requires 7 clicks of elevation, set the dial so that the number 2 brings the sight to 7 clicks from the bottom.
2. Battle zero the rifle. There are several methods to do this, which you can research. Generically, you zero the rifle for 200 yards or meters, and calibrate the elevation drum so that the line between 2 and 4 brings the sight to this position. At this setting, you can engage any target from 0 to 300 yards/meters, with a couple of inches of elevation change in either direction depending on the range. Get to know your holds as the range changes, and this especially critical when the range is under 100 yards/meters. With some additional work you can extend to 500 yards/meters without adjusting the sight by learning the holds.
 
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