Zero in a used ACOG

[Repro77]

Hi,

I have a used TA01 ACOG, and was wondering how to go about zeroing it in on my AR15. Do I have to start from somewhere, such as bottoming out the adjustment screws and starting from there? Of course, I have no idea how it was adjusted prior to me getting it, and no manual came with it.

Any help would be appreciated!

 

[supernova]

Mount it and shoot a group at close range. Make necessary adjustments then move out further. It should be on paper at 25 yds. And remember, click values @ 25 yds are 1/4 value of what they are at 100. So if it has 1/2" clicks @ 100 then each click will be 1/8" @ 25 yds. If it has 1/4" clicks at 100 then its 1/16" @ 25. Shoot a group, roughly measure how far off it is in inches, multiply that measurement by the number of clicks required to move POI 1" @ 25 yds, dial scope and shoot again to confirm. Then move out further.

 

[shawn]

Start from a mechanical zero.

Bottom out the adjustment and count the clicks until it reaches the other limit and divide by two. Do that for both windage and elevation, that will be the sights mechanical zero.

Then complete what supernova said.

Shawn

 

[Repro77]

Thanks, I'll give all this a try.

 

[Trinimon]

Easiest way:

Mount optics to upper.
Remove upper form lower.
Remove BCG/Charging handle
Lay upper on a flat surface with a target 25-50yrds in the distance
Sight down from behind the upper down the bore and make note of what is in the middle of that sight picture
Without moving the upper, sight down the optic.
Note where the reticle is located
Using the elevation/windage dials, move the reticle over to what is in the middle of the bore's sight picture so that both the bore's sight picture and reticle are identical

Your optics should be on paper now and you just need to fine tune it.

Mount upper to lower and setup on a solid benchrest
Fire a round and note the impact on the target
If you have a sighting-in-target with properly marked out grid pattern, you can now adjust your reticle based on how much MOA/MIL per click
If you don't have the proper target, without moving the rifle from the last shot, sight down the optic and using the elevation/windage adjustment dials, move the crosshair over to the bullet impact mark.
Fire a round to confirm zero and fine tune if needed.

Sounds like a lot to do but it'll probably take you less time to complete it than it took to read it all.

 

[shawn]

Thanks, I'll give all this a try.

Starting for mechanical zero also gives you the advantage to use the optic on multiple firearms without much fuss. Just record your zero from each gun and you are good to go ie:

10/22: E= 22 clicks from bottom W= 5 clicks from left
SKS: E= 99 clicks from bottom W= 1 click from left
glock 17: E= 10 clicks from bottom W= 40 clicks from left

Then quick three shot group to confirm and your good to go.

Shawn