I zeroed AR at 50 yrds using A2 carrying

[nathan]

handle with the adjustable rear sight.I performed the Santose Improved battlesight by unscrewing the set screw and 4 clicks clockwise, then tighten. I then counterclockwise the elevation knob down -4 clicks. I zeroed at 50 yrds . I adjusted the front sight post so it hits POA. Now I was using the small peep hole on the A2 rear for precision shooting but i just read now that i should have used the bigger hole for sighting the rifle

. My question is, if i use the bigger peephole right now, and shoot it again at 50 yrds, would the bullet hit POA or it will be slightly higher or lower? I understand the the big peep hole is for combat application or low light situation, right ?
BTW i was using 55 gr FMJ cheap Russian made ammo which grouped quite well. The upper is PSA 16 inch CHF with 1:7 twist. AFter i zeroed at 50 yrds with this ammo , i tried a few Prvi Partizan 62 gr green tip to see if it has the same POI. It was a little left and not as tight. Hmmm, it seems like this barrel likes 55 grners.

Thanks

 

[CaptTripps]

I would think if everything else in unchanged, except for the larger diameter rear peep. Your POI should be the same. Assuming the centers of the peeps are in the same location. I would think your groups would open up slightly.

 

[crazysccrmd]

The two peep sights are on different planes and will change your POI slightly. This post is a decent explanation of how it works and the effects.

http://www.ar15.com/forums/t_3_18/497571_0_2___The_A2_Rear_Sight_Aperture.html

 

[MistWolf]

Some large peeps are set to be zeroed at 100 when the small peep is zeroed for 200 (or maybe 250?) While others are set so the zero is the same. You'll have to go shoot your rifle to find out if poi changes and if so, how much

 

[nathan]

The large peep i have has the 0-2. I have to shoot this again when i get the chance to see the difference.

 

[DMK]

There is definitely an elevation shift. According to the M16A2 Operators manual (TM 9-1005-319-10) the large "Short Range" aperture is for 0-200m and the small "Normal Range" aperture is for 300-800m

For the Santos IBZ, Col Santos recommends setting the elevation drum two clicks down from the 8/3 setting with the small aperture for the 50y/200m zero and setting the elevation drum right on 8/3 for the larger aperture in order to keep the same zero.


XS Sight systems sells a direct replacement "Same Plane Aperture" that keeps the large "ghost ring" and small peep at the same elevation. These are especially handy for BUIS and A1 carry handles where there is no elevation drum and you want a consistent zero.

 

[dfariswheel]

You should not use the larger aperture sight.

Current military practice is to always use the small aperture for all shooting except for shooting at close range moving targets or when shooting at night.

For those interested, there are two Colonel Santose battlesight methods.

One sets up the sight so that you can shoot on the typical American ranges that are set up for yards instead of meters.
Using this method you can be on target at 25 and 300 meters, and by changing the sight you can be on target at 50 yards, and 100 and 150 yards.

Using the other Santose method you can be on target at 25 and 300 meters, and by changing the sight you can have a battle sight that will allow hitting a target within FIVE INCHES at ANY range from zero to 230 meters.
That means aiming dead center and you will be no more than 2 1/2 inches low at long ranges up to 230 meters, and no more than 2 1/2 inches high at closer ranges.
In any case, you can hit a target within no more then 2 1/2 inches high or low.

There are methods for use with the rifle sight that goes up to 800 meters, and the carbine sight that goes to 600 meters.

http://www.ar15.com/forums/t_3_18/328143_.html

Simpler read:

http://www.ar15.com/content/page.html?id=599

I set my Colt M4 up for the 50, 100-150 yard methods and it really does work.

 

[DMK]

I zeroed at 50 yrds . I adjusted the front sight post so it hits POA. Now I was using the small peep hole on the A2 rear for precision shooting but i just read now that i should have used the bigger hole for sighting the rifle

In the original IBZ, Santos actually recommended using the small aperture and zeroing at 50y, then verifying zero at 200m.

My question is, if i use the bigger peephole right now, and shoot it again at 50 yrds, would the bullet hit POA or it will be slightly higher or lower?

Yes the POI would be lower with the larger ghost ring and this would be appropriate for close range. IIRC it works out to around a 100y zero for the large ring and a 200M zero for the small peep (without any changes to the elevation drum).



.

 

[DMK]

In case anyone is confused, here's the original IBZ in its entirety:

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An Improved Battlesight Zero for the M4 Carbine and M16A2 Rifle

1. Current Army/Marine Corps battlesight zero and it's procedures are well described in TM9-1005-319-10, the M16/M4 operator's manual. A recent copy of this manual is available for download at the Manual Depot </TheMarylandAR15ShootersSite/ar15manuals.msnw>. Procedures in the manual will not be repeated here.

2. The current 300 meter battlesight zero is a function of the sights on the rifle and I personally find it shoots too high for the vast majority of combat targets, including the Army's qualification ranges. The procedure listed here takes better advantage of the flat trajectory of these rifles as well as the use of civilian ranges, which are seldom surveyed in meters.

3. When zeroed at 200 meters, a distance twice that of normal combat engagements, these rifles have a very flat trajectory that is less then 2" from line of sight at all intermediate distances; a distance that's smaller than the normal dispersion of arsenal or factory loaded ammunition. This tiny trajectory arc allows very precise shooting out to 250 meters where the bullet is only 2" below line of sight.

4. A 200 meter zero has the happy coincidence of an initial trajectory cross-over at 50 yards, a distance available on almost all civilian ranges including many indoor ranges. This makes it easy to achieve a 200 meter battlesight zero without recourse to surveying your own range. If 200 meters is available you can fine-tune the zero at the real distance. And should when you get the chance.

5. The lowest sight setting, however, on these sights is 300 meters so the sight needs to be modified to preserve the markings on the sight (despite the fact that no one ever sets a range on these in the real world other than a USMC range). The sight needs to be set to bottom out at 8/3 -2 clicks. This will be the new 200-meter setting.

1. Flip the rear sight back to the unmarked aperture. This will reveal a hole in the top of the handle.

2. Rotate the sight wheel all the way down. Will probably be exactly at 8/3 (6/3). Don't force it down.

3. Using a 1/16" Allen wrench loosen the screw (under the revealed hole) in the sight wheel 3 full turns. Leave the wrench in the screw.

4. Rotate the bottom half of the sight wheel two clicks clockwise. This will raise the sight body if you look at it while you're turning it.

5. Tighten the Allen screw, remove the wrench, and confirm the sight bottoms out at 2 clicks BELOW 8/3. If not repeat the procedure until it's right.

6. Battlesight the rifle per the -10 with the following exceptions:

1. Sight should be at 8/3 -2 clicks, that is, all the way down, not up a click. Please note removable handle sights are marked 6/3 (rather than 8/3); also some are in ‘half-clicks’ as well. There should be 3 clicks between 3 and 4 on the knob. If there are 6 clicks then the sight needs to be set at –4 clicks (instead of –2).

2. Small aperture, nose to firing handle weld.

3. Distance is 50 yards.

4. Point of aim should be point of impact of bullet.

7. Remember you're adjusting the FRONT SIGHT for elevation, not the rear, and that each click is about 1/2" (actually a little more) at 50 yards. You won't get it closer than that. Don't frustrate yourself trying.

8. You're done. Leave the sight in this position for 99% of your shooting.

9. If you have to shoot targets you KNOW are 300 meters away or more, just click to the right number on the sight.

10. If you're patrolling, set the sight to 8/3 and snap the aperture forward to 0-2. This will provide the same trajectory as above but with a larger, easier to see thru rear sight. Use this setting if you also have the M68 mounted as it's quicker to transition to if the sight fails.

11. If you have an M68 CCO (Aimpoint CompM-XD) optical sight battlesight it to 50/200 as well. You can shoot to 300 meters by merely holding "over a dot."

12. This battlesight zero is valid to 300 meters for both the M16A2 and M4 Carbines and their AR15 sisters. It's valid with any ammunition that approaches the specs for M193 (55gr) or M855 (62g) Ball ammunition. It works for both rifles and carbines due to the offsetting influence of higher muzzle velocity in the rifle being offset by the longer sight radius that moves bullet strike less per click. This is battlesight, not X-ring shooting!

13. This battlesight zero does not reflect the doctrine of the US Armed Forces, however, it reflects the personal use of these weapons in combat and in training for over 34 years.

14. Comments to: Lt. Colonel Chuck Santose ([email protected] <mailto:[email protected]>).

Note To Users of Carbines with the A1 style rear sight or users of Flip-Up Sights: This 50 yard zero works really well. If you have the original sight aperture use the unmarked (short range) hole to zero the rifle. If you have upgraded, and use the A2 style aperture (or the A.O. Same Plane sight), then use the small (long range) hole for zeroing.

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[Malamute]

despite the fact that no one ever sets a range on these in the real world other than a USMC range

Interesting, I use the longer range markings quite a bit, I think the A2 sight is very good for irons for shooting at distance. I wish they had a bit more range to them.

 

[DMK]

Note that for the A2 carry handle sight, all Santos is doing is giving you a few more clicks down from 8/3 on the elevation drum to give you an unmarked 200m zero with the small peep. (where the mil spec has 300m/800m as the lowest setting)

If you click the drum up to 8/3, you are back at at a 300m and all the other range markings still work. (again with the small, precision aperture)

I wish they had a bit more range to them.

You shoot AR15 irons past 800 meters?