Question on zeroing my AR15

[Lugnut]

I have a new AR15 (Bushmaster) and I took it to the range to sight it in- establish zero at 25 yds. The way I understand this is that once you set it up properly at 25 yds, your rifle with be set at 300 meters as well (battlesight I guess) and then you can use the elevation dial to hit target properly at 300, 400, 500, etc yards. I'm pretty darn sure I was using a correct sight picture/alignment but the bullets were grouping high to the right. I had to move the windage knob 10 clicks and the front sight about 10 clicks counter clockwise to get the groups centered. Is this much adjustment normal? It was NIB. The groups were about an inch so although it's not perfect they were moving the way I expected.

The other question is why do you need to use the Normal Range Aperture instead of the Short Range Aperture? It didn't seem to effect the location of the groups and the Normal Range Aperture was more difficult to use at 25 yards.

Also since I have an A3 upper I had to zero it in with the elevation knob 2 clicks higher. Why do you need to do this? Is it because the bullet will intersect the sight line at 25 yds and 350 yds?

Thanks in advance.. this is all new to me and I'm dying to understand this more.

Good thing is I shot my G27 at 30 feet after (non adjustable sights) and the thing is dead on! Apples and oranges.. and I like em both!

 

[Admin]

That amount of adjustment is normal. My first M16 had a BZO of 21 left. The smaller the rear sight apreture the more accurate you will be. In the Marines small was for day, larger was for night.

 

[Martlet]

Any amount of clicks is pretty normal to get your zero. What affects that the most is your sight picture. It all depends on where your cheek hits the stock.

I'm not sure what you mean by "short" and "normal". The **EDIT** LARGER sight is used for distances up to 200 meters or so. That's the one you want to zero with.

 

[Lugnut]

Any amount of clicks is pretty normal to get your zero. What affects that the most is your sight picture. It all depends on where your cheek hits the stock.

I'm not sure what you mean by "short" and "normal". The smaller sight is used for distances up to 200 meters or so. That's the one you want to zero with.

Thanks for the answers guys.

Martlet- the manual says you should use the short aperture (bigger hole) for distances up to 200 yds and you use the normal aperture (smaller hole) for 300+. You use the normal aperture to zero in at 25 yds though.

 

[Martlet]

Thanks for the answers guys.

Martlet- the manual says you should use the short aperture (bigger hole) for distances up to 200 yds and you use the normal aperture (smaller hole) for 300+. You use the normal aperture to zero in at 25 yds though.

Then the manual is wrong.

 

[Martlet]

Thanks for the answers guys.

Martlet- the manual says you should use the short aperture (bigger hole) for distances up to 200 yds and you use the normal aperture (smaller hole) for 300+. You use the normal aperture to zero in at 25 yds though.

Hmmmm. Edited to check.

 

[Martlet]

You made me second guess myself so I had to walk through it.

When I zero my rifle I use the small aperature. The mark used for setting mechanical zero ( the lazy way) is on top of the larger one.

 

[Cledus J. Crabb]

When I set the zero on my A2 Bushmaster @ 25 yds. I was lucky enough to have it fall right on the money, windage wise. All I had to do was make a very minor adjustment at the front post.
A few others I know have had trouble setting the zero because of an off-centered front sight base, which required a major adjustment for windage.
In both cases, Bushmaster made good on it.

 

[Admin]

Martlet,

The Army doesnt teach a different aperture for different ranges does it? I've been through that qual course 3 times and I don't recall hearing it. Night time fire or NBC gear is when you use the large one.

 

[centermass181]

the big app is for 0-200 meters, (thats what the 0-2 means), AND nightfire, AND NBC. but come on, who really aims during NBC?

 

[Martlet]

Martlet,

The Army doesnt teach a different aperture for different ranges does it? I've been through that qual course 3 times and I don't recall hearing it. Night time fire or NBC gear is when you use the large one.

That's how I was taught, but that was 20 years ago. I second guessed myself because when I came back in and qualified recently, the range instructors were yapping that I was using the wrong one. I told them thanks, but I'd use what I was comfortable with. Perhaps that's the reason I was the only one on my line that went 40/40.

I looked online just now and saw the large aperature is for short range, small for long. Makes no sense to me, though.

 

[Lugnut]

Ok... so I think I get this just fine now... but why do you need to move the elevation knob to lowest setting (6/3 on mine) and then crank it up two notches when zeroing in at 25 yds? I'm sure it works but my mind will remember this better if I understand. Thanks!

 

[Admin]

Ok... so I think I get this just fine now... but why do you need to move the elevation knob to lowest setting (6/3 on mine) and then crank it up two notches when zeroing in at 25 yds? I'm sure it works but my mind will remember this better if I understand. Thanks!

It's always good to have some room left on your elevation to go down below your zero.

 

[Kalahari]

I was told yesterday at an AR-15 clinic that the larger aperature is really for faster aquisition of targets since in battle you aren't looking for a perfect bullsye, just a torso hit.