Why Army and Marines have differnt zero standards?

AR/M4 AR General Discussion
1

I got interested in this a few days ago when I was wondering what the best method of zeroing a standard 16" OAL 556, I had always been told to zero optics and sights to 100 yards. I asked some guys at my LGS and one guy said 25-300 meter and another guy said 36-300 yard. I then learned that the Army teaches meters and the Marines teach yards. Then they went into talking about astrophysics, ballistics, quantum mechanics and started talking about BZO and how zeroing at 25 meter, 36 yard, and 50 yard is only to get you on paper and close to where you should be shooting at 300 meters, 300 yards, and 200 yards. I didn’t understand a word of it yet I nodded and told them it made perfect sense and thanked them.

For a civilian with a 16" OAL 556, what is the best approach to zeroing BUIS, red dot & Peq-15? All the same or slightly different?

2

For zeroing, Stickies have this covered:

https://www.m4carbine.net/showthread.php?65679-AR-15-Zeros-and-Trajectories
https://www.m4carbine.net/showthread.php?171434-AR-15-Zero-Graphics-Various-barrel-lengths-and-zero-ranges-M193-M855-and-Mk262
https://www.m4carbine.net/showthread.php?107572-Zen-of-the-100-Meter-Zero

As to why army and marines are different in teaching, I thought they both used meters, something to do with artillery ranging standards that drifted over to everything else (MILS ?).

3

I’ll just leave this here…

//youtu.be/0yddJGlJo7c

4

looks like the 200 yard zero is best all around. 2.5 inch combat effective zone.

5

Another freat thread:
https://www.m4carbine.net/showthread.php?171434-AR-15-Zero-Graphics-Various-barrel-lengths-and-zero-ranges-M193-M855-and-Mk262

6

I don’t know where you got the Marine Corps only uses yards. According to MCRP 3-01A, Rifle Marksmanship (USMC), Chapter 8, the pre-zero range for the Back Up Iron Sight (BUIS) is given as “33 meter/36 yards” (page 8-10). This is most likely due to some of the older range complexes being from the pre-metric military era. However, this publication further states the final (official) zero shall be conducted at “300 meters/yards”, the practical difference between the two, 25.7 meters or 28.1 yards, depending on which way you go, has little impact on combat effectiveness.

As to why they zero differently is due to the differences between the two services qualify. Since the USMC still uses the Known Distance (KD) range for qualification, the rifle is zeroed at 300 meters (or yards depending on where the range’s firing point are actually located) to align with the 300 meter/yard prone rapid stage of qualification, which is considered “Battle Sight Zero”. Moving the sights to the 200 mark for the short range stage and going up to the 600 mark for the long range stage.

The Army doesn’t like to mess with the sights, and so uses a 25 meter zero range, with the sight set at special places depending on weapon type, then never touches the sights again. Since the Army qualification is at “E” and “F”-type silhouettes that pop-up and a hits are scored as either “hit” or “miss”, being a foot from your point of aim low or high at 300 meters is not that big a deal (unless you have lousy fundamentals).

The trajectory of a bullet fired passed through the line of sight twice, once at short range as it travels upward and once when it passes through the zero range. For any given muzzle velocity and sight height, this two ranges are fixed. With M855, fired from a 20 inch barrel will cross the line of sight at 33 meters and 300 meters, which is how the USMC manual reads. Per the Army manual, you adjust the rear sight of an M4 to 3/6 and use the small aperture and zero at 25 meters then switch to the large aperture, which theoretically gives you a zero at 300 meters.

Why the Army goes through this complex drill of sight adjustment is due to the fact that the Army has long used the “1000 inch range” (25 meters) for qualification for machine guns, and they have a lot of them next to longer range complexes, and they never felt the need to move the target stands back 11 meters…

To better understand each service’s qualification methods, rather than listen to “some guy”, read the actual manuals, they can be found on-line for free

ARMY: FM 3-22.9 - Rifle Marksmanship M16-M4 Series Weapons (Aug 2008, w/ chg 1)
USMC: MCRP 3-01A - Rifle Marksmanship (11 Oct 2012)

As to how you should zero, zero at the most likely range you will be shooting.

7

I zero at 50 and have no issue hitting 10” steel plates at 300 yards.

8

WTF?? With a 100 yard zero your POI will be low at 0-50 yards, NOT high like Haley demonstrated above. Not really sure how he came up with that. Really strange.

9

Maybe people should stop worrying about what the military is using and instead pick the zero that is appropriate for their optic and typical engagement range.

10

< like this post >

I zero at 100, because that is my max probably civie engagement range.

Inside of that, an inch low is still a hit. In general I prefer low hits to high hits.

First mistake… :smiley:

11

Lysander you write: “Per the Army manual, you adjust the rear sight of an M4 to 3/6 and use the small aperture and zero at 25 meters then switch to the large aperture, which theoretically gives you a zero at 300 meters.” I don’t think that is quite correct. You will have a 300 meter zero using the small aperture but when you switch to the large aperture you will have a shorter zero that would give hits between 0 to 200 meters. If the range is at 300 meters then the small aperture would be used and if you know the ranges beyond that you would use the click adjustment up to 600 meters. Of course the trick is to correctly estimate the range. It is one thing to shoot at known distances and another to shoot at unknown distances which is why the Army does not use a known distance range.

12

To me the missing part on all this is with red dots, we aren’t talking about a clear defined aim point like you have with a aperture/post with a round bull and what is the capability of the gun-ammo-shooter. Maybe I’m more sensitive to the sight part with my astigmatism and the fact that any dot bright enough to see clearly is going to bloom to some degree for me. Sure, I turn them down when zeroing, but then add in for most military guns with MIL ammo, what is the standard? About 2MOA, IIRC- and that was just for the ammo.

So you have at least a 2MOA dot, and about a 2MOA gun- so together probably a 3ishMOA jiggle- of 9 inches at 300. I know everyone here shoots better than that, but it sure seems that during most comps not many people are consistently shooting common-spec set-ups that well.

So basically, I was always trying to find out how to best make it so that my shots would land inside my red dot, or deviate least from it- and if it did deviate, have it be in the most predictable and useful way.

13

Let me ask this: Say you have a standard 16"OAL barrel M4. You have BUIS, Aimpoint Micro and a PEQ-15. Should your optic and laser be set to the same standard like the red dot and the visible laser combine into what looks like one seamless dot at say 50 yards? Or should you zero your red dot at one distance and your laser to another? I have heard a lot of people say to best way to zero your optic is to position the red dot to match the BUIS line of sight. I think that is for close distance, possibly 100 yards. So I tried that in my garage at 46’ which is the width of my garage and spend some time getting my laser to match the red dot but if I take my gun outside the red dot and laser are literally feet apart. What would be a good combination to get my red dot and laser to be close enough where I could just use a laser if I chose so. I have a KAC NVG riser and my T-1 sticks up higher than my KAC sights.

14

25, 36, 51-Meter zeroes are all hasty band-aids to get sights close.

It ain’t a zero until you’ve verified at true range that it’s zeroed.

Red dots, pointers, aimers, illuminators, and irons? Rough zero, then confirm at the ranges you are demanding hits. If you’re shooting E-types at 100 then confirm at 100. Center-of-mass at 300? Shoot at 300 and confirm your shots are hitting point-of-aim.

15

As the saying goes, The Bullet never lies.

16

The frustration lies in access to suitable rifle ranges that accommodate 200 or even 300 yards or meters. I feel fortunate to have a good 100 yard range that is well maintained. At the end of an outing to “zero” a rifle, the best I can do is a drop chart and set of dial calipers. I really wonder how many members here are spoiled enough to stretch their legs on a longer walk to the bullet stop.

17

Im a fan of the 50/200 zero. With that zero I aim center mass from 0-300 yards and get good hits.

Elephant… Its been a long time since I zeroed a PEQ, like 2005, but if I remember correctly we had a specific target for zeroing those. Its was just “align the laser to the red dot” kind of thing.

18

No because your laser is offset to the SIDE of your sights. If you zero it to exactly where your red dot is zeroed you will experience left or right offset depending on the range just like vertical offset with a red dot except your laser intersects with your red dot at only 1 point. You should be zeroing your laser next to your red dot at whatever side you are placing your laser. That way you will have a consistent side offset no matter what the range.

Think of it this way. Draw an X. Where the two lines meet is where you are zeroing your laser to your red dot. At every other range in that drawing your bullets are doing in impact anywhere along the line to the right or left of the center of the X. Now draw 2 parallel lines ||. Now you have a consistent offset distance between the two lines that you have to memorize. Ie. my bullet is always impacting 3 inches left of my laser versus having to know my bullet will impact 5in left at 100m then 9in right at 50m ect.

19

Exactly. Same thing with an M1 Garand or Dragunov clone and their offset scopes.

20

Well all I know is that my POI is always low when I run my drills anywhere from 5 to 30 yards, not high. I’m zeroed at 100. Still baffled as to Haley’s results.