Co-Witness zeroing

Yoshi · Oct 13, 2011

Probably a dumb question, but when co-witnessing, does anyone zero their red-dot different from their irons? As in, say, the red-dot at 50yds and the irons at 100yds?

I've read several different methods:

Red-Dot aligned with front site post - both zeroed to a certain distance.
Irons in lower 1/3 of red-dot site picture.
Etc...

Haven't heard of using both for differing distances since you're supposed to see both through the glass, right?

lx1x · Oct 13, 2011

it should be the same.. your iron sight is acting as backup to the red dot..

clandestine · Oct 13, 2011

Zero for 50 yards with your red dot and align the irons to the red dot. Youll be good from 50 to 200 yards with tat single setting.

boardboy330 · Oct 13, 2011

I do the 25m zero method on both. Then test it at 100m to verify.

SCARCQB · Oct 13, 2011

Each sight should be zeroed independently. I zero the Irons first at 50 yard BZO, then the Red Dot.

In absolute co-witness configuration, Irons and RDO may not always align , even if zeroed at the same distance.

Chris L · Oct 13, 2011

I also zero my irons first, then adjust the dot to the front site. Here's an example of my lower 1/3 co-witness:

Shift my cheek weld slightly and use red dot only

04RWon · Oct 13, 2011

Clandestine has the right idea. Hes making it a little easier. You can actually do it either way, red dot first or irons. Basically you get one dialed in, then get the other to co witness and that will give u a base. Your first shot should be pretty close to where you want. You might need a little fine tuning.

A plus to having both zeroed the same, is if you ever think one is off, you can flip up the sight or turn on the dot and check allignment.

04RWon · Oct 13, 2011

Its funny how we automatically assume its an ar hes talking about lol

Kevp · Oct 13, 2011

Yoshi said:
Probably a dumb question, but when co-witnessing, does anyone zero their red-dot different from their irons? As in, say, the red-dot at 50yds and the irons at 100yds?

I've read several different methods:

Red-Dot aligned with front site post - both zeroed to a certain distance.

Irons in lower 1/3 of red-dot site picture.

Etc...

Haven't heard of using both for differing distances since you're supposed to see both through the glass, right?

How would you not see both through the optic? The only way this could happen that I can think of is if your irons were screwed up to begin with such as using a short Picatinny rail gas block that is sits below the plane of the upper receiver rail with a front sight that is too short (made to mount on the same rail plane as the receiver rail). This would cause you to have to elevate the gun in order to see the front sight through the rear peep.

The two generally accepted co-witness variations that you will see are the absolute co-witness where the irons are centered in the RDO field of view, and the lower 1/3 co-witness where the irons are in the lower 1/3 of the RDO field of view. The later is more popular as the RDO sight picture is less cluttered.

You do not want to zero your BUIS and RDO at different distances as the irons are a back-up to the RDO and you want the same POA/POI with both.

I only use Aimpoints, but have used EO Techs on both issue and personal rifles. I have found EO Techs harder to zero, period. That said, I recommend that you zero your BUIS first at whatever your preferred distance (I use a 50/200). I then dial in the RDO so that the dot sits right on top of the FSP. I then start firing 3 round groups to zero the RDO. With Aimpoints, I usually only have to make minor adjustments to zero. EO Techs have always caused me headaches and I think it has to do with them having 1/3 MOA increments. YMMV.

Notes:
-Remember to use the small aperture when zeroing your BUIS/irons or you're going to be chasing a zero and wasting lots of ammo.

-Do not try to align the red dot with FSP and center it in the rear aperture or you will be all screwed up. Zero and shoot them independently and remember that once that dot is properly zeroed, as long as you can see it and put it on the target, you will hit what you are shooting at (if all your other fundamentals are sound)- it does not have to be centered in the optic FOV or aligned with irons.

04RWon · Oct 13, 2011

Hes right...i feel like i always have to move my eotech. My aimpoint and strikefire, once, maybe an adjustment next trip, then leave em.

Yoshi · Oct 13, 2011

Thanks! I was thinking (bad idea) that it could be used for multiple distances. Just thought it could give you multiple aiming/reference points.

Forest · Oct 13, 2011

Yoshi said:
Probably a dumb question, but when co-witnessing, does anyone zero their red-dot different from their irons? As in, say, the red-dot at 50yds and the irons at 100yds?

I've read several different methods:

Red-Dot aligned with front site post - both zeroed to a certain distance.

Irons in lower 1/3 of red-dot site picture.

Etc...

Haven't heard of using both for differing distances since you're supposed to see both through the glass, right?

"Irons in the lower 1/3" or "irons in the center" of the optic relate to mount height - not a different zeroing method.

In either case if you look through the irons and they are zeroed for the same distance the dot will appear to sit on the front sight.

Personally I prefer my irons in the lower 1/3 of the optic - which leaves the optic display less cluttered. It also means I have to shift my cheekweld slighlty if I want to use irons - so be it as I haven't had an optic fail on me yet I only use the BUIS to keep up with my iron-sight skills.

Half-cocked · Oct 13, 2011

boardboy330 said:
I do the 25m zero method on both. Then test it at 100m to verify.

Assuming you're talking about an AR15, then you're doing this:

vs. this:

SRD · Oct 13, 2011

I've been folowing this trying to understand/edumacate myself,but holy crap.I never saw the trajectory of .223 before.This is nuts,thanks for posting.

Half-cocked said:
Assuming you're talking about an AR15, then you're doing this:

vs. this:

Kevp · Oct 13, 2011

Yoshi said:
Thanks! I was thinking (bad idea) that it could be used for multiple distances. Just thought it could give you multiple aiming/reference points.

Yoshi,

I recommend that you go to Viking Tactics website and buy Kyle Lamb's book- Green Eyes & Black Rifles. It will answer every question you have on the AR platform. In this case, you need to understand the ballistic tables for your chosen ammunition. You probably shoot 55gr. There are ballistic tables for Federal XM 193, M855, MK262, and Federal 62gr Bonded. What makes these tables great is that he breaks down bullet drop from 25 to 400yds with zeros at 25, 50, 100, and 200m. What this does is allow you to choose a zero that best fits your needs. For instance, the military uses the 25/300 zero. A lot of guys think that is "the zero" because that is what they learned in the military. Most civilians aren't going to shoot an AR beyond 200yds. For 55gr XM193: the 25/300 zero will be 5.86" high at 100yds; 8.26" high at 150yds; and 9.31" high at 200yds. The 50/200 zero will be 1.39" high at 100yds; 1.56" high at 150yds; and .36" high at 200yds. So which is the better all-around zero? The 50/200 zero allows you to aim CoM and achieve good hits from contact distance all the way out to 200yds without adjusting your POA (remember we're talking CoM, not head shots- offset is another discussion for inside of 50 and trying to hit a brain box for instance). Hope this helps.

Tower43 · Oct 13, 2011

36/300 is optimal...

It's called BZO, or Battle Sight Zero. (don't ask why its not BSZ, its the military)

at 36 yds the trajectory is the same as 300.

the 300, with the 0-2 (0-220 Meter) large opening rear peep sight is for close quarters battle. Anything under 30M should be point and shoot, reference and front sight tip only (Takes practice... aka instinctual shooting)

Just saying the Marines (And AFIAK the other services) have been doing it this way for years..... and it worked in combat... just saying

Kevp · Oct 13, 2011

Tower43 said:
36/300 is optimal...

It's called BZO, or Battle Sight Zero. (don't ask why its not BSZ, its the military)

at 36 yds the trajectory is the same as 300.

the 300, with the 0-2 (0-220 Meter) large opening rear peep sight is for close quarters battle. Anything under 30M should be point and shoot, reference and front sight tip only (Takes practice... aka instinctual shooting)

Just saying the Marines (And AFIAK the other services) have been doing it this way for years..... and it worked in combat... just saying

The drop charts don't lie. The Services have been doing a lot of things for years for which there are better answers and there are more than a few top professionals in the industry, most being vets, that advocate getting rid of that zero. One in particular, known for saying "Just sayin'" that happens to be a former Marine Gunner.

04RWon · Oct 14, 2011

Tower43 said:
36/300 is optimal...

It's called BZO, or Battle Sight Zero. (don't ask why its not BSZ, its the military)

at 36 yds the trajectory is the same as 300.

the 300, with the 0-2 (0-220 Meter) large opening rear peep sight is for close quarters battle. Anything under 30M should be point and shoot, reference and front sight tip only (Takes practice... aka instinctual shooting)

Just saying the Marines (And AFIAK the other services) have been doing it this way for years..... and it worked in combat... just saying

236 years next month :party29:

Kevp · Oct 14, 2011

Good article on the merits of the 200 (Improved BZO) over the 300 zero.

Again, being able to compare the ballistic tables for these two zeros is where you really see the merits of the 200 over the 300.

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

Forest · Oct 14, 2011

Tower43 said:
36/300 is optimal...

It's called BZO, or Battle Sight Zero. (don't ask why its not BSZ, its the military)

at 36 yds the trajectory is the same as 300.

the 300, with the 0-2 (0-220 Meter) large opening rear peep sight is for close quarters battle. Anything under 30M should be point and shoot, reference and front sight tip only (Takes practice... aka instinctual shooting)

Just saying the Marines (And AFIAK the other services) have been doing it this way for years..... and it worked in combat... just saying

That's a USMC zero. Yeah it works, but for most people the 50 works better as it has a flatter trajecotory in the ranges most people shoot at.

With a 50y zero you can hit a beer can with a center-of-mass hold from the muzzle out to 225 yards or so.

If you have range adjustable sights (MaTech, KAC600M, LMT, Carry Handle etc) you can set the sights to bottom out at 200M (zeroed at 50y) and the elevation numbers still work.

For those with Military A2 type rear sights you can easily reset your dial to bottom out -2 clicks (for fixed handled A2 sights) or -4 clicks (for detachable handles & LMT type sights) below the 300M setting. So at the bottomed out position it will be 200M, and the elevation numbers will be calibrated correctly (for M855 at least).

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