Zeroing my A2 Bushmaster

[DougH]

The official Army zeroing procedure (http://www.armystudyguide.com/content/army_board_study_guide_topics/m16a2/zero-and-m16a2-rifle.shtml) seems straight forward enough, but my problem is I don’t know how I’m going to do it based on what I’ve experienced so far. They tell you to

1) Front sight flush with top of sight post.
2) Rear sight elevation one click beyond the 8/3 position (rear sight elevation has an 8/3 position on the dial and then (with intermediate clicks), rotates one full revolution through 4, 5, 6, 7 and then back to 8/3. Total range 300-800yds). So, I guess the “one click beyond” the 8/3 is lower and used just for zeroing.
3) Rear sight windage zero.
4) Distance 25 Meters.

Note: After setting the rear sight elevation to that one click beyond the 8/3 position, all elevation zeroing is done with the front sight post. After that, the front sight post is never changed again.

My problem is that up to now, when at the NRA HQ Range shooting 150ft and 1), 2) and 3) applied, I’ve had to aim way low already. I can't imagine that I could have raised the front sight enough to lower the strike of the bullet to the point I could have aimed at center mass. Maybe it will be different at only 25 Meters (approx 75 Ft)? I don’t want to put my long front sight post on… but may have to in order to both zero it and shoot from 200-600 yds. You can’t really raise the front sight post very many click from zero.

I will be shooting "Across the Course" this weekend from 200, 300 and 600 yds.

My questions to the forum are 1) Have you had to use a long front sight post to zero your A2 AR at 25 meters and 2) Do you shoot from 200-600 yds with your AR and, if so, do you use a long front sight post?

 

[WNTFW]

DougH,
Welcom to THR.

I'm not sure I get your issue. (It's probably me). I don't get where you have it zeroed now.

If you have a 100 yd zero you will need to come up about 16 MOA to 600yds.
200 yd zero will have to come up about 14.5 MOA to 600yds.

I say about due to variables like ammo.

I have shot a 20" inch AR @200 / 300 / 600. It was zeroed @ 200yd. I had to add 1.5 MOA from 200 to 300. I had to add 13 MOA from 300 to 600yds. It was not my rifle. It was a loaner. I literally picked one off the the tailgate of a truck.

Brownells has a sight correction calculator that you can plug some numbers into. The have a sight height calculator as well.

I'm sure some else may give you a better answer.

One of my best shooting experiences was AR service rifle @ 600yds.

Good luck on everything. I hope you have a good match. Please follow up here with some results.

 

[JoeSlomo]

I have never had a problem needing "more" front sight to properly zero irons at 25 meters, however, I have never made a zero attempt at 50 meters with irons, as I do not like the characteristics of a 50 meter zero.

Using a 25M zero with standard ball and irons, I have successfully used the irons out to 800M, though beyond 600, it became quite the challenge for me.

The Army uses 25 meters because with the standard M855 round, a point of aim / point of impact zero at 25 meters will result in the round being pretty close to point of aim / point of impact at 300 meters. This type of zero results in a maximum ordinate of about 7", and allows a shooter to aim center mass of man sized targets out to 300M without having to make any elevation adjustments. The "line of death" for typical soldier accuracy occurs at around 200 meters, so the Army is satisfied with the characteristics of this zero.

A point of aim / point of impact zero at 50 meters, on the other hand, will result in the round being closer to a point of aim / impact at 200 meters. This zero technique has been adopted by some units because it is more suitable for the typical soldier (who has a hard time hitting targets beyond 200 M), and because the maximum ordinate is only around 2 inches out to 200 M, which makes it easier to hit targets with the typical center mass sight picture.

I'd recommend using either a 25 M zero, and collecting data at range, OR, researching what your fellow competitors are using for ammo and zero technique, and capitalize on their success and knowledge. The information I provided stems from military M855 ammo, so your results WILL vary.

Good luck.

 

[DougH]

TNTFW, You're so right, I don't have it zero'd now. I guess what I was trying to say was that with the front sight zero'd, and the rear sight elevation that one click below 8/3, if I aim center mass at 150 ft, I hit so high that I don't think I can raise the front sight from zero enough to bring the bullet down far enough.

I'll go to the NRA HQ range tomorrow and try the Army procedure and get back to everyone.

 

[WNTFW]

DougH,
Did you get the rifle new or used? Reason may be the FSB (front sight base) may be the wrong height for the rear sight, resulting in a mismatch.
I have been in the position of hastily trying to get a zero at 50yds to be on paper at 200. Unkowns are harder to deal with. Ammo is a variable also. If you don't know how much it drops you don't know where to go. Confidence in your hardware is an advantage.

If you are close go & observe the match if you have not been to them. Someone there may know what to do to fix the problem. At first I thought I could shoot a match but not spectate. Now, I would probably get something out of just watching.

You could shoot a dry fire match at home.

I'm sorrry I can't be of more help.