Sighting in AR with EOTECH


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alphabrace
July 15, 2010, 09:33 PM
Friend of mine just got an Eotech sight for his AR. Any suggestions on what range to sight it in at? I was thinking if you sight it in at 25 yds it will be on at 100 yds and if you sight in at 50 yds it will be on at 200 yds. Old wives tale? Any help is appreciated. Thanks!

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gb0399
July 15, 2010, 09:39 PM
for a 300m zero POI will be 3/4" below POA at 25m

briansmithwins
July 15, 2010, 10:05 PM
Zero at 50 yards.

You'll be +-2.5" out to about 250 yards.

Google Improved Battlesight Zero.

BSW

Guitargod1985
July 15, 2010, 11:29 PM
I zeroed mine for 100 yards, which gives me the following POI using M193 ammo:

-1.5" @ 25 yds
-0.7" @ 50
-2" @ 200
-10" @ 300

At 400 yards, the POI comes to about 26-27" below POA, but I've never shot that far with it, and can't even imagine how wind would affect a 55gr projectile at that distance.

be aware, however, that a 100 yard zero gives a much more exaggerated ballistic trajectory than either a 25 yard or 50 yard zero.

Mainsail
July 16, 2010, 02:38 AM
The eotech should come with instructions on the best way to sight it in.

C-grunt
July 16, 2010, 04:06 AM
Do the 50 yard zero. 25 yard zero is back on at over 300 yards a very high at 100 yards.

wideym
July 16, 2010, 04:18 AM
I zeroed my rifle using a 300m reduced size zero target. Once my rifle's backup iron sights were zeroed, I simply used the BUIS to zero my EOtech by dialing it to match my BUIS.

briansmithwins
July 16, 2010, 12:35 PM
I zeroed my rifle using a 300m reduced size zero target. Once my rifle's backup iron sights were zeroed, I simply used the BUIS to zero my EOtech by dialing it to match my BUIS.

I'd say you're 1/2 done. I've used the same method myself but you really ought to confirm that the optic is zeroed by actually shooting it.

I usually get the optic within 4" or so at 50 yards by referencing the irons. BSW

Fremmer
July 16, 2010, 12:39 PM
What's the EOTECH like shooting at 300 yard targets? Is the target partially or entirely covered by the dot?

RP88
July 16, 2010, 01:28 PM
from my experience, it seems pretty much covered.

This is because the EOtech has a minor bloom to it. It can come off as "grainy", but it hasn't let me down. It is more of a reflex sight than it is a precision sight - remember that.

rcmodel
July 16, 2010, 02:23 PM
Very precise shooting can be done with the Eotech at longer range if you turn down the brightness until you can barely see the 1 MOA dot.

At high brightness settings, it becomes very pixelated and imprecise for shooting small groups, or small targets at long range.

Turned down low, it is just as capable as your eyes are to be able to define the 1 MOA dot on the target.

Here is 10 meter bore sight target from Eotech:
http://www.eotech-inc.com/documents/M16A4-M4MWS_EOTech_LBS_Target.pdf

Here is 25 meter zeroing target from Eotech:
http://www.eotech-inc.com/documents/M16A4-M4MWS_EOTech_Live_Fire_Target.pdf

rc

gb0399
July 16, 2010, 02:26 PM
the eotech works great at 300, but thats about the practical limit.

gb0399
July 16, 2010, 02:27 PM
+1 to RC, always shoot with the sight at the lowest power setting for maximum accuracy.

rcmodel
July 16, 2010, 02:30 PM
Again, the practical limit depends on how good your eyesight is.

I'm 65 years old and wear bifocals.
But if I can see it well enough, I can hit it.

Somewhere around here I have some targets with 1" five shot groups I shot at 100 yards off a bench with an Eotech and a Colt AR-15 carbine while testing handloads.

rc

AK103K
July 16, 2010, 06:31 PM
I have Aimpoints on my AR's, but I would assume this would work with the Eotechs too. The easiest way Ive found to get the dots rough zeroed, is to use the iron sights, and put the "dot" on the front sight post, just ever so slightly below the tip, with the irons set to the range I'm trying to sight in at. I always confirm and fine tune the zero after I "set" it, and I've always been pretty close doing it this way.

4thPointOfContact
July 17, 2010, 01:47 PM
I played around with a ballistics computing program and went back and forth between the 25 and 50 yard zero's. The best compromise was actually about 37 yards but good luck finding where you can do That. I have my AR adjusted just a bit low at 25 and it's minute-of badguy out as far as I'm likely to engage in civilian life.

benEzra
July 17, 2010, 04:54 PM
I am a strong proponent of the 50-yard zero for the Eotech's sight height (7.2cm over bore). According to iSnipe, the trajectory looks like this on a cold day (a warm day would give you about a half-inch less drop at 300) using 55gr ammunition with a ballistic coefficient of 0.243:

Yards................Point of Impact
5 yards....................2.5" low (use the bottom of the ring to aim)
10 yards...................2.2" low (use the bottom of the ring to aim)
15 yards...................1.9" low
20 yards...................1.6" low
25 yards...................1.3" low
30 yards...................1.0" low
40 yards...................0.5" low
50 yards...................right on
75 yards...................1.0" high
100 yards..................1.7" high
125 yards..................2.1" high
150 yards..................2.1" high
175 yards..................1.8" high
200 yards..................1.1" high
225 yards..................0.1" low
250 yards..................1.7" low
275 yards..................3.8" low
300 yards..................6.5" low
350 yards.................13.7" low
400 yards.................23.7" low
450 yards.................37.0" low
500 yards.................54.2" low

Here's a 100-yard zero instead, under the same conditions as above:

Yards................Point of Impact
10 yards...................2.4" low
25 yards...................1.7" low
50 yards...................0.9" low
75 yards...................0.3" low
100 yards..................right on
150 yards..................0.4" low
200 yards..................2.3" low
250 yards..................6.0" low
300 yards.................11.6" low
400 yards.................30.4" low
500 yards.................62.7" low

You can see that the 50-yard zero puts the bullet at the line of sight a little sooner, while also giving you considerably less drop beyond 200 yards, at the very small cost of being ~2" above the line of sight between 100 and 150 yards. I think that's a good match to the capabilities of both the .223/5.56x45mm cartridge and the Eotech as a sighting system.

What's the EOTECH like shooting at 300 yard targets? Is the target partially or entirely covered by the dot?
The optical limit of a human eye with 20/20 vision is 1 MOA (1 arcminute). So in digital-camera terms, a 3-inch target at 300 yards will be about one "pixel" wide to the human eye, a 6-inch target will be about two "pixels" wide, and an 18x18-inch target will be six "pixels" wide by six high. The Eotech dot at low brightness will appear one "pixel" (1 arcminute) wide at all distances and under all magnifications, so assuming no magnification it would completely cover a 3" target, half cover a 6" target, and obscure about one sixth the width of an 18" target. Of course, someone with 20/40 vision will see the Eotech dot as being twice as large as someone with 20/20 vision sees it, so if your vision is worse than 20/20 then the dot will obscure more of the (blurry) target. Ditto if you have astigmatism or are looking through the edges of thick glasses, which is a problem with all optics.

In my experience, the greatest difficulty in shooting at 200+ yards with an Eotech and no magnifier is difficulty seeing the target clearly, rather than obscuration of the target by the Eotech's dot.

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