MBUS sights on an AR - zeroing

[Fitz]

So... I got a magpul back up rear sight for my AR.

Mounted it, fiddled with the thing. Found my m4 25 meter zero target...

Looked at the sight

WTF

Where's my elevation? On the backup irons I'm used to there's still an elevation adjustment (and a place to use for 25m zero range)

So, if I want this thing to have a 300m zero, and I'm using an m4 zero target, where should my point of impact be at 25m?

[Fitz]

Pretty knowledgable friend says a 50 yard zero will also give me a 200 yard zero. Thoughts?

[41magsnub]

That person is correct.  I use the aimpoint 25 yard targets for the 50m/200m zero both for the aimpoint and the BUIS.  The 25 yard part is nice since that is where the close target backers are at all the ranges around here.

http://home.comcast.net/~j_colt123/25%20Yard%20Zero.pdf

Wrong target, that one is for a 50 yard/200 yard target.  Somewhere out there is a version of that target reflecting what I talked about.

[dogmush]

The 50/200 thing is correct.

If you want a 300 zero on a 25m target, pull the TM and read the zeroing instructions for an M68 CCO. It'll give you the right offset. I don't remember right now, and my TM isn't handy, but I'll try to find it.

[Fitz]

Thanks!

Here is a pic! Primary arms red dot on the way also

[dogmush]

At 25m the offset is 1.4cm down.

That is, aim for COM of the standard zero target, and adjust sights so that your group is 1.4cm (1 and 1/2 squares) below COM.

[AZRedhawk44]

I'm too lazy to go look out in the safe at my MBUS setup on my .22 AR but I believe there is no elevation adjustment on the rear sight.

There are two apertures on the rear, one that nests inside the other.  Similar to the flip-up/down 0-2 and 300+ apertures on an M-16A2.  Windage adjustable only.  You adjust elevation by moving the front sight up or down.

I'd set the small aperture to 300, and check to see if the larger aperture is slightly lower by 2MOA, like the A2 configuration.  

But... zero at 25 meters (not yards), and you'll have a 300 meter (not yards) zero with M855.  And as long as the larger aperture is also dropped/offset by 2MOA then you'll have an effective BSZ with that one for closer shots, too.

[dogmush]

Ummm. That's not how the A2 sights work.

[AZRedhawk44]

Ummm. That's not how the A2 sights work.

I know.

But the MBUS rear sight has two apertures like the A2 sight.

They do not have elevation adjustments like an A2 sight has.

[dogmush]

I know.

But the MBUS rear sight has two apertures like the A2 sight.

They do not have elevation adjustments like an A2 sight has.

The MBUS apertures are cowitnessed. One is bigger than the other.  The bigger one is for night/close shooting.  A2 sights work the same way.

FWIW, while I know it does adjust the elevation of the rear sight, that big wheel on an A2 sight is a range adjustment wheel.  You're not supposed to use it for zero adjustments.

[AZRedhawk44]

The MBUS apertures are cowitnessed. One is bigger than the other.  The bigger one is for night/close shooting.  A2 sights work the same way.

FWIW, while I know it does adjust the elevation of the rear sight, that big wheel on an A2 sight is a range adjustment wheel.  You're not supposed to use it for zero adjustments.

Right.  You zero with the front sight, with A2 sights.

MBUS have no elevation adjustment of any sort on the rear sight.

[dm1333]

Here is a pic! Primary arms red dot on the way also

Which red dot?  I had a chance to look through some red dots, magnifiers and a Leupold 1.25-4x scope this weekend.  I think I'm going with the Burris MTAC, especially if I can mount if far enough forward that the MBUS rear sight will still flip up.

[dogmush]

I really like my strikefire

[dogmush]

Right.  You zero with the front sight, with A2 sights.

MBUS have no elevation adjustment of any sort on the rear sight.

I think we're saying the same thing, and I just had a reading comprehension fail.

[dm1333]

I really like my strikefire

That is one of the two red dots I have been considering. The SPARC looks pretty good but uses some oddball battery, the Aimpoint PRO is the other red dot I have been considering.  I'm not buying anything until I get a chance to do some more research.  At one gunshop one of the employees had his AR with the Leupold mounted and it was easy to use both eyes with the scope turned down to 1.25X. 

[Fitz]

Right.  You zero with the front sight, with A2 sights.

MBUS have no elevation adjustment of any sort on the rear sight.

Yes, hence my problem.

With M16/M4 sights, you set the elevation for zeroing, zero (POA=POI) then click it back to the 300 m setting.

With this, there is no such setting of elevation.

But, since 50 yards has same POI as 200 yards, i'll just do that for both the CCO and the MBUS.

lower 1/3 cowitness. Schmexy

[Hawkmoon]

Pretty knowledgable friend says a 50 yard zero will also give me a 200 yard zero. Thoughts?

I thought a 25 meter zero was a 200 meter zero. I've forgotten -- and it's probably different for an M4 with 62-grain ammo than it was for an M16 with 55-grain anyway. I'm using an optical scope with a bullet drop compensator good to 500 meters, so I don't get overly concerned about my iron sight zero.

Google 'Battle sight zero"

[brimic]

Yep- just do the 50/200 zero- it works and is arguably the most versatile zero.

I really like my strikefire

+1

[Boomhauer]

It's A1 style sights. Elevation adjustment is all done with the front sight. None of that A2 bullshit with two different methods of adjusting elevation. Yeah it's coarser but they are backup sights, not match sights. I favor the 50/200 zero myself.

[Gewehr98]

How did bovine excrement make it past the naughty word filter?   

[Fly320s]

Another vote for 50/200 zero. It gives you point blank range from 0 to about 225 yards. Point Blank defined as not having to change your point of aim to hit inside an 8 inch circle.