37 Yard Zero with ACOG & BDC Reticle

[Blockhead]

Was chatting with an ex-Marine at the range yesterday. He shared that he learned to zero the ACOG with a target at 37 yards using the 300m Aiming line (second down from the chevron). He said this would set point of impact at the top of the chevron for 100m, first line below it at 200m and so on with M193 55gr ammo. He shared that his unit used this method for setting/checking zero in the field.

Can anyone verify if I got this right and share any experience using this method for the game? Sounds like it would save a lot of time.

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[kurtm]

Yes in general a 37 yard "zero" is about a 300 yard zero, depending on bullet and velocity, but I think I would want a bit better read on it than that and would zero at the farthest distance available. Remember any little difference at 37 yards due to bullet weight and velocity is completely masked, where as farther out it really starts to play a huge difference! I find most folks don't like shooting groups far away because it is hard to get a "good" group. Think of shooting at 200-300 yards for group like eating broccoli....you may not like it, but it's good for you!

[Chuck Anderson]

This makes no sense to me. Why not just zero at 100 for the top of the Chevron? How many people have access to a 37 yard range? Is it because they can't group at 100? Or better, do what Kurt suggests and zero at 300, or whatever range you can get to. That said, I'm actually considering switching back to zeroing at a shorter range to take wind out of the equation.

[Steve RA]

One problem some of us have who reside in large cities is that you may have to travel quite a ways to find a range that will have facilities for over 100yds. If you can zero @ 100 you can then wait until you get "out of town" to check sight settings for longer ranges.

With a chronograph and the BC of whatever bullet you use you can get a pretty good idea of what your sight settings may be for longer ranges. This should get you in the ballpark until you can confirm by actual range time at the longer distances.

[kurtm]

Yes Chuck it is because the military shooters can't group, and it takes a ton of time to shoot further away, This way it saves ammo, it is close enough, and besides we aren't really a shooting military culture much anymore.

[Bryan 45]

Chuck- funny you mention zeroing at closer range to eliminate wind shift.

I've used the bushnell 1-6.5 for a few years now, with mil reticle. I zero the dot about 2" high at 100, which gives me a good true windage zero. Then go back to 300 and adjust the turrets so that using the -1 mil hash is dead on at that distance. If I have a noticeable windage shift, I blame it on actual wind. (Unless it's obvious that's not it.)

[Graham Smith]

IF I remember this right...

The standard zero distance for iron sights is 25 meters (27 yd) which also put's you at zero at 300 meters. Is it possible that you got the distance wrong?

The height above bore for an ACOG is going to be different on a flat top than it would if mounted on the carry handle. That's going to effect the ballistics so it may be this is what the 37yds refers to.

[kurtm]

Not quite, The impact at 25 meters is supposed to be 3.6 cm low (1.5" about) that means the bullet is still climbing into the sight, which roughly correlates to a 37-43 meter zero for a 300 meter zero, more or less so the idea of a 37m zero on your 300 m stadia mark is about right. and don't forget the Corps is still running 20" barrels.

[Stlhead]

I think that everyone should adopt this method of zeroing. Think of the ammo and time that could be saved, not to mention the range time that could be freed up. If it is good enough for the US government it should be good enough for us.

[Steve RA]

"If it is good enough for the US government it should be good enough for us."

[TonytheTiger]

All of my friends (2 total) have spent time in Afghanistan and they both tell me that practice/zeroing time and ammo are very hard to come by, and more importantly the ranges they have inside the wire rarely go past 50 meters. I was told they usually zeroed at 25 meters and if they were keeping 20 slow fire rounds in a 4" circle on a reduced size silhouette that the gun/optic was considered "close enough".

[bmiller]

All of my friends (2 total) have spent time in Afghanistan and they both tell me that practice/zeroing time and ammo are very hard to come by, and more importantly the ranges they have inside the wire rarely go past 50 meters. I was told they usually zeroed at 25 meters and if they were keeping 20 slow fire rounds in a 4" circle on a reduced size silhouette that the gun/optic was considered "close enough".

This is why I thank Vets for their service every chance I get. We owe them more than this!

[TonytheTiger]

Yes we do.

[SonOfSpartans]

What does it really matter as long as you know your dope? I zero a fifty as dead on as I can. Then check my ballistics for how high I should be at 100. Shoot a few groups to confirm.

This allows verification puff both windage and provides a second check on trajectory. Routinely shoot to 600 plus and the dope is accurate.

BDC reticles are trouble without data. One rifle will have a first mark impact at 289 yards and another will be 312 with the same ammo on a standard day.

If your calculator has your score information and an optimizing function you can use that to get your marks close to round numbers. You may find that you can find a near zero yardage but may have to use an offset like a quarter inch or so.

One size fits all will not get his for all.

I apologize if this sounds opinionated or snarky, it is not meant to be. Our club shoots a lot of longer games and it is enlightening. If you feed random ammo and go to 300+ the results can be disastrous. The right ammo/gun/dope at 300 can get boring.

[Graham Smith]

Not quite, The impact at 25 meters is supposed to be 3.6 cm low (1.5" about) that means the bullet is still climbing into the sight, which roughly correlates to a 37-43 meter zero for a 300 meter zero, more or less so the idea of a 37m zero on your 300 m stadia mark is about right. and don't forget the Corps is still running 20" barrels.

You're not talking about the old Canadian bull target are you? I seem to remember that could be used for either a 250m or 350m battle sight zero depending on whether you were hitting the upper or lower X. Dang, that's really stretching my recollection. But back then, I think everything was done in yards not meters.

I was referring to this target:

http://www.armystudyguide.com/content/army_board_study_guide_topics/m16a2/zero-and-m16a2-rifle.shtml

But in either case, I think you are correct because in both of these methods, you are either not hitting where you aim or you have to make a correction afterwards.

Edited August 26, 2015 by Graham Smith

[kurtm]

A Canadian bull??? I guess no one raised those where I grew up, Does it look like a Brahma, or a Charolais?

[bmiller]

Charolais are much tastier, not as stringy.

[Alaskapopo]

Yes in general a 37 yard "zero" is about a 300 yard zero, depending on bullet and velocity, but I think I would want a bit better read on it than that and would zero at the farthest distance available. Remember any little difference at 37 yards due to bullet weight and velocity is completely masked, where as farther out it really starts to play a huge difference! I find most folks don't like shooting groups far away because it is hard to get a "good" group. Think of shooting at 200-300 yards for group like eating broccoli....you may not like it, but it's good for you!

What Kurt said. A close range zero is a good place to start but if you have the range confirm out as far as you can.

Pat

[DocMedic]

Not every infantry Soldier/Marine is a marksman... They are told the minimum of what they need to know to be able to suppress and hopeful kill the enemy while support by fire comes in (240B's, A-10s, Apaches, Kiowas, Bradley's, etc etc)

When Zeroing a new scope I'll take a few shots at 37 yards to make sure I'll be close to paper when I fine tune at 300 yards.

Edited August 27, 2015 by DocMedic

[Steve RA]

"Not every infantry Soldier/Marine is a marksman... "

And that is really sad, especially for front line troops !!!

[kurtm]

Every Marine is a rifle man first and foremost, but sadly what you say is true.

[DocMedic]

And that' is really sad, especially for front line troops !!!

The catch 22 isn't it. Killing the Enemy is important, but fire supremacy is King for maneuvering. 1 bullet or 1000 the job will get done

[Graham Smith]

It's worth bearing in mind that the original post is about a field expedient way of setting/checking the ACOG (presumably the 4x) on the Marine M16, which is designed to be zeroed at 100m. It's done using the 300m mark on the BDC.

Trying to zero a 5.56 with a 4x optic at 300m introduces a lot of variations that can make that difficult. Certainly it would be nice to check it at that distance, but the whole idea behind a battle sight zero is to zero at a shorter distance where small variations introduced by the shooter and the environment can be minimized.

Edited August 28, 2015 by Graham Smith

[Eric_Vmax]

OK, just to get this straight, with my standard competition ammo, if I go to the range and zero at 37 yards (in door range is close and has only a 46 yard bay) with the 300 yard dot on my BDC, than I am "good to go" at what power? I have a 1.5 to 6 BDC

[RiggerJJ]

OK, just to get this straight, with my standard competition ammo, if I go to the range and zero at 37 yards (in door range is close and has only a 46 yard bay) with the 300 yard dot on my BDC, than I am "good to go" at what power? I have a 1.5 to 6 BDC

No, it will put you close. When able verify at 300 (or 200 if that is desired zero range) and adjust as needed.