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View Full Version : Was using the M4 at the range today with iron sights


Cobrafreak
05-15-2010, 11:20 PM
I dialed it in at 25 yards with the large aperture rear sight and when I got to the 100 yard targets I could not hit the paper unless I put the rear aperture to the small hole which I believe is supposed to be 200 yards. I had to redo my initial 25 yard zeroing so I could do this. It must be my eyes. I need the small hole at 100 yards or I just not going to hit the paper. I will just need to remember with the large aperture I will be shooting a little low at under 100 yards. I know they sell different aperture sizes for AR rear sights. Is this normal? Anyone else have this problem?

maxwellca21
05-15-2010, 11:34 PM
what type of ammo are you using? reload?
where did you get the rear sight? brand name?
is this a new rifle? who install your sight for you?

reidnez
05-15-2010, 11:37 PM
The apertures are not ranged differently on any standard AR15 sight that I know of. You should be getting the same point of impact with either, though most shooters are (logically) less accurate with the large (O2) aperture. So, it is an issue with your sight picture--operator error, I'm afraid. The 02 aperature is for faster acquisition or lower light situations, I never use it at the range. If you shoot fine with the small aperture, why not just use that?

Cobrafreak
05-15-2010, 11:56 PM
The apertures are not ranged differently on any standard AR15 sight that I know of. You should be getting the same point of impact with either, though most shooters are (logically) less accurate with the large (O2) aperture. So, it is an issue with your sight picture--operator error, I'm afraid. The 02 aperature is for faster acquisition or lower light situations, I never use it at the range. If you shoot fine with the small aperture, why not just use that?

I'm leaning this way. I am thinking the 02 would be for home defense, close quarter combat situations, but at any distance the small aperture would be best for me.
I know there is an elevation difference between the small and large (02) rear aperture because if I zero it on 02 with my aimpoint co-witnessing and flip from large 02 to small aperture the zero will be at the next red dot elevation. Don't know the brand of rear sight. It's an A2 rear sight without the carry handle which is on my flat top that is on the rail. I'm assuming some manufacturers have no elevation change between big and small and others do. Right?

pipboy
05-16-2010, 12:03 AM
Which sight(s) were you using? For instance the apertures on the Magpul MBUS rear sight are not same-plane between the small and large, so there is a differential in POA/POI switching between them.

Cobrafreak
05-16-2010, 12:19 AM
Which sight(s) were you using? For instance the apertures on the Magpul MBUS rear sight are not same-plane between the small and large, so there is a differential in POA/POI switching between them.

Which site? A2 rear sight model with windage and elevation without carry handle. It attaches to a flat top upper. Don't know manufacturer. But I do know that there is a range difference between large and small hole, with the small hole being slightly taller for distance. It's so minute that I would never have noticed without having my aimpoint on co-witnessing.

Cobrafreak
05-16-2010, 12:37 AM
Found this on the web. Pretty much explains it.

" An A1 aperture has two holes that appear to the be the same size. One has no markings on the base, while the other has "L" marked on the base. The one with no marking is your 0-200m aperture, and the "L" marked aperture is for 300m-800m.

An A2 aperture has a large hole and a small hole apertures. The large hole is marked 0-2 which is designed for 0-200m ranges. The small hole has no markings and is for 300m-600m for short sight radius weapons, and for long sight radius weapons 300m-800m.

What people don't realize is that generally when you switch from the 0-200m aperture to the long range aperture it will raise your zero approximately 6.5" at 100yds. "

So if I shoot better at 100 yards with the small hole on my 02 sight, I will be shooting slightly lower with the large hole at closer distances as there is a range difference between small and large hole. I can live with this.

You-Two
05-16-2010, 3:06 AM
These links might help you out and answer your questions at the same time!

http://www.fsguns.com/ibsz.html

http://www.ar15.com/forums/topic.html?b=3&f=18&t=328143

reidnez
05-16-2010, 8:13 AM
Well dang Cobra, I stand corrected! You just taught a Marine something about the M16 :). I guess I should research before I spout off!

Funny none of our PMI's ever mentioned that. I guess it just didn't come up because we never used the O2 on the range. IMO, for a service rifle, the small aperture is a bit too small and the O2 is a bit too large.

Also, for typical home defense ranges (0-7 meters): you can pretty much sight down the barrel or "point" with your supporting hand, and you will hit. Practice it at the range.

corrupt
05-16-2010, 7:25 PM
Well dang Cobra, I stand corrected! You just taught a Marine something about the M16 :). I guess I should research before I spout off!

Funny none of our PMI's ever mentioned that. I guess it just didn't come up because we never used the O2 on the range. IMO, for a service rifle, the small aperture is a bit too small and the O2 is a bit too large.

Also, for typical home defense ranges (0-7 meters): you can pretty much sight down the barrel or "point" with your supporting hand, and you will hit. Practice it at the range.

Yes, the PMIs in boot camp tend to try to keep it simple since it's generally a lot of info to teach someone all at once if they've never fired a weapon before. However, this is why a 300 meter zero (Marine BZO) is done specifically with the small aperture.

Remember, we must master the basics before going crazy on the optics (my opinion anyway). Irons are more fun to shoot anyway (for me).

KING_PALM
05-16-2010, 8:02 PM
Pfl

Call_me_Tom
05-16-2010, 8:51 PM
An M4 has a 14.5" barrel...

I've shot an M4 out to 500 yards. You need to work on your shooting fundamentals.

pyromensch
05-16-2010, 9:07 PM
Well dang Cobra, I stand corrected! You just taught a Marine something about the M16 :). I guess I should research before I spout off!

Funny none of our PMI's ever mentioned that. I guess it just didn't come up because we never used the O2 on the range. IMO, for a service rifle, the small aperture is a bit too small and the O2 is a bit too large.

Also, for typical home defense ranges (0-7 meters): you can pretty much sight down the barrel or "point" with your supporting hand, and you will hit. Practice it at the range.

when did you serve.
i was schooled, that the large aperture, (different these days), was for 200-300 yd/meter range), and the small aperture was 500 yd/meter range. (78-82)

Donk310
05-16-2010, 9:50 PM
Yes, the PMIs in boot camp tend to try to keep it simple since it's generally a lot of info to teach someone all at once if they've never fired a weapon before. However, this is why a 300 meter zero (Marine BZO) is done specifically with the small aperture.

Remember, we must master the basics before going crazy on the optics (my opinion anyway). Irons are more fun to shoot anyway (for me).


EXACTLY!!