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Old 14 February 2019, 07:06
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Let's discuss Zeros.

Now here is a subject, that goes round and round, and one I play with a lot.

What is your preferred zero for you rifle?

Basic Army zero is at 25 meters. Drill Sergesntbtold us "Hold a little low between 150 and 200 meters, hold a liitke high past 300 meters." Gets you "minute of man". Seems to keep you close for less than 25m also, where most engagements for CQB/home defense would take place. But of course at closer ranges you will have poi lower than your poa.

Many though prefer a 50m or 100m zero, as keeps with inches between 50 and 250.

Marines are doing a 36m zero - of course they all sporting Acogs. ; )

There are of course considerations regarding applications.

And also if zeroing, many time one may only have access to a 25m range or 50m range.

No matter what you zero at, know where you are at and what compensations you have to make at various distances.

I usually zero my hunting rifles at 50m, since most my shouts will be between 25-100 meters and that gets me within that 6" diameter kill zone with poa.
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Old 14 February 2019, 07:18
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Most people just don't understand the basic geometry of zeroing. Your bullet is going to cross your line of sight twice, once on the way up, once on the way down. If you have a rifle with a high line of sight,vs line of bore the angle is sharper to get say a 25yd zero, which puts you up there pretty high at mid range. If you're a deer hunter and plan to shoot 100yd, zero at 100 and just know how low your going to be at 200/300. If you put on a sharp enough angle to be zero'd at 25, you're going to be high at 100. There are plenty of programs out there to figure these things with some basic info like sight height, etc.
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Old 14 February 2019, 07:40
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100m on my personal rifles as I dont see using them to shoot further than that.
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Originally Posted by leopardprey View Post
Marines are doing a 36m zero - of course they all sporting Acogs. ; )
IIRC, the logic behind the 36m zero is it gives you the 300m dope for your M16 while not requiring the long range, scoring targets, etc.
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Old 14 February 2019, 08:34
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This is going to be a good thread.

Going receive only except to mention that the sitelite brand laser boresights have an app that does a good job of graphically representing the sight line/ bullet path intersections. I've used it a few times to explain the concept, easier than trying to explain a ballistics table.

Now shutting up
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Old 14 February 2019, 08:38
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Quote:
36m zero is it gives you the 300m dope for your M16 while not requiring the long range, scoring targets, etc
They've figured out at what range/LOS/LOB need to intersect to have the bullet cross line of sight again @ 300. Diff sight height vs irons, hence the diff zero range.
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Old 14 February 2019, 08:57
Shark0311 Shark0311 is offline
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It depends. If you have a BDC reticle then you would zero according to the specifications of the optic and round it's designed for.

On the other hand if you have a ranging reticle then you might zero based upon the objective. Say you plan on working medium ranges, a 300 yard dope then build a come up table for rapid engagement. For medium to long range you might start at 400 or 500 yards depending on the ballistics of the round and expected engagement distance.

It's not a one way or another type of thing. It's a tool to be manipulated for the mission.
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Old 14 February 2019, 09:00
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Quote:
It's a tool to be manipulated for the mission.
Sure. I was talking in generalaties across the spectrum of sights. Basic understanding of the geometry is the key, once you master that, the specific system can be adapted to easily.
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Old 14 February 2019, 09:16
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Let's say a Zero for your standard citizen owning a AR type rifle, or a police officer with their AR rifle, with iron sights or a 1x Red dot? Where most of your engagements are going to be probably within 7 - 50 meters. Maybe if live out on a farm/ranch or LE work you could see an occasional longer shot for self defense/neutralizing threats.


What is best for your standard Infantryman to have?


Your thoughts. 25, 50, 100, 200 zeros?
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Old 14 February 2019, 09:22
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Originally Posted by Gsniper View Post
Sure. I was talking in generalaties across the spectrum of sights. Basic understanding of the geometry is the key, once you master that, the specific system can be adapted to easily.
Absolutely. Just to elaborate a bit for the OP:

On the M16A2 with irons you would use a 25 yard zero with the 8/3 -2 setting for a 200 yard dope then adjust the sight for the correct range. 8/3 for 300 yards etc.

The ACOG if I remember correctly is zeroed at 36 yards for a 300 yard dope due to the BDC reticle. A BDC reticle is designed to be zeroed at a fixed distance with a specific round.

Last edited by Shark0311; 14 February 2019 at 09:38.
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Old 14 February 2019, 09:25
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Quote:
Originally Posted by leopardprey View Post


What is best for your standard Infantryman to have?


Your thoughts. 25, 50, 100, 200 zeros?
The irons are designed to be zeroed at 200 or 300 yards. The ACOG at 300.

At short ranges (<25, 50, 100) the bullet rise / drop is negligible negating the need for a close range zero.

For CQB distances you hold high depending on the height of the sight over the bore axis. Usually between an inch or two.

Last edited by Shark0311; 14 February 2019 at 09:31.
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Old 14 February 2019, 09:58
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That's why on my 551 I have BOTH a reflex and a scope with a ranging reticle.
-Reflex (CQB) is zeroed at 25
-6X Scope is zeroed at 100
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Old 14 February 2019, 10:04
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Modern technology has made this question easy to suss out: Pick your Caliber, Bullet Weight, Ballistic Coefficient, Height Above Bore, and Muzzle Velocity out of your Barrel Length - and plug it into a Ballistic Calculator like:

http://www.shooterscalculator.com/ba...+Create+Chart+

That is for my preferred SD round, but you can get that data for any round, off the mfgs web site. Notice you can hold basically 'dead on' out to 200 (7.5" AR Barrel). Aim at the base of the neck at 200 (-4.48") if you want to be picky.

You can then change your zero range and look the the numbers, and pick whatever trajectory suits your situation.

The thing that I get a chuckle out of, is the universal: "Bro, 50/200"... yeah, if your shooting M855 out of a 20"

Change the Chart Step Size to 5yds, above, you'll see that 62gr with a 0.31 BC at 2200fps, gives you a 50/125-130 zero.

If you can, then confirm in the real world - but you won't be *that* far off for Joe Citizen self defense.

Edit: Changed some stuff a smidge - Boat Tails should use the G7, and not the G1 Drag Function - ranges/drop changed a bit, but not drastically.
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Last edited by Polypro; 14 February 2019 at 10:34.
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Old 14 February 2019, 10:09
Shark0311 Shark0311 is offline
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For example with a 300 yard zero on an M16A2 the bullet rise maxes out at ~6 inches at 160 - 200 yards, ~4 inches at 100 yards and ~1.5 inches at 50 yards.

In this case you can hold low, shoot minute of man or adjust to 8/3 -2.

Last edited by Shark0311; 14 February 2019 at 10:19.
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  #14  
Old 14 February 2019, 10:26
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How about just knowing where your POI is for different distances based upon the capabilities of the firearm? Anything less is failure to prepare and just lazy. Who cares if you have a 25/36/50/100/200 zero as long as you know your holds?
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Old 14 February 2019, 10:28
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I zero 5.56 and .308 at 100 yards.

On my AR and Tavor I've got 3x Acog optics so I just follow the directions for the reticle. It's easy, fast and simple.

On my Styer THB I have a Nightforce ATACR 4-16x and I just adjust the turret to get the point of impact I want.
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Old 14 February 2019, 10:38
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I've been using Frank Proctor's "50 yard zero at 10 yards" method for a few years on my ARs.
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Old 14 February 2019, 10:44
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Quote:
Originally Posted by 275RLTW View Post
How about just knowing where your POI is for different distances based upon the capabilities of the firearm? Anything less is failure to prepare and just lazy.
+1000, getting data on your gun in the location that you'll be working in is the key. Temperature and pressure effects the ballistics of the round. If you're working at 10,000 ft elevation in the winter you can't rely on data gathered at sea level in 80 degrees.
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Old 14 February 2019, 10:59
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Hmmmnn ... interesting replies so far.

Great subject LP.
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  #19  
Old 14 February 2019, 11:33
havok88 havok88 is offline
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On scoped rifles I like a 100 yard zero, but with red dots I prefer 50, because it has relatively little change out to 250
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Old 14 February 2019, 11:42
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No wrong points in the thread, for sure. Know your dope, realize atmospheric changes, confirm in real world if possible. Access to proper length ranges can be a problem for some, and may dictate zero range. I think the point, at least to me, is to pick a range that minimizes having to do math in the heat of the moment - whatever that equals, for you.

Here's LC M855 with an averaged MV of 2850 - which should be close for 14.5" Pinned, as well as 16". Height Over Bore is 2.5" which coincides with anything with an Absolute Co-Witness with Irons:

25 Yards

http://www.shooterscalculator.com/ba...+Create+Chart+

36 Yards

http://www.shooterscalculator.com/ba...+Create+Chart+

50 Yards

http://www.shooterscalculator.com/ba...+Create+Chart+

100 Yards

http://www.shooterscalculator.com/ba...+Create+Chart+


I would not recommend 25 Yards, unless using the standard GI Rotary Drum rear sight/procedure. I thought the page had an error when calculating 25, until I remembered that to zero at 25, you actually dialed it down a couple clicks, zeroed, and then clicked it back up to 8/3 - IMO 25 yards with a Red Dot would be a nightmare.
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