AR flip up rear sight question or scope suggestions

[Guest]

I will be starting my next build within the next month. My last build had a varmint upper which was scoped. I am doing a tactical build for tactical rifle shoots when my build is complete.

Instead of having the carry handle, I am thinking about putting a flip up rear sight. Would the flip up rear sight be compatible with the standard front sight when mounted on the uppers rail.

Anyone reccommend a good scope for close quarter shooting? I may even get an EOTech.

Please post your recommendations and your experiences with EOTech sights while shooting or in general.

[low94noma]

I have also heard mounting the EOTech closer to the barrel nut will prevent wandering of your sight to help keep your sight on target? Any further information on this. I have also seen flip up rear sights that co-witness with an EOTech. Any advantages to having both mounted together on the rail?

[RobG]

The rear sights are the same height. Its the front that is different between rail mount and gas block mount. I loved my EO when I had it. Unfortunately my eyes need some mag. now so I sold it

[low94noma]

Thanks for the input. My new shooting glasses are now my prescription glasses unless I am shooting close quarters or long range shooting with a scope. I am near-sighted, so far my vision is not that bad, although I am still young, we'll see within the next 10 years. I think having both a flip up rear and the EOTech is for a backup in case the EOTech fails or for longer range. Hmm.

[hawk81]

Go with the magpul sights.

[low94noma]

Go with the magpul sights.

Are they all co-polymer like the mags? Or are their sights a mix between metal and polymer such as the aperture?

[low94noma]

I mean is the aperture a different material other than co-polymer?

[Dr Rockso]

I mean is the aperture a different material other than co-polymer?

The aperture is plastic. I'm unsure as to whether it can be replaced with a standard aperture, but I don't believe so.

[low94noma]

Magpul has a good rep and their mags are fine with me, I am just worried about the quality of their sights. Looking at a Troy Industries flip-up rear. Not sure about what model EOTech yet. I still have a month or 2 to decide.

[maxicon]

At the risk of sounding rude, ignore anyone who says "use X" without knowing what your needs and budget are. The Magpul's fine for some uses, but won't fit under many scope/mount combos, and takes up more rail space than others. Make sure it fits your needs before you buy.

As RobG said, all rear sights are the same height when deployed - it's one of the few solid standards in AR optics. There are big differences in how you can use them, though - aperture sizes, folded height, how much rail they take up, how they deploy and lock, etc.

For the Eotech, it doesn't matter where on the rail you mount it, as long as the front of it doesn't touch the handguard. If you've got a fat M4 handguard or a railed handguard that's even a little higher than the rail, it limits how far forward you can mount it without touching the handguard. The side-button Eotechs are raised to better clear the handguards and provide lower 1/3 co-witness, or you can get a riser to do the same.

It shouldn't wander anywhere on the flat top rail as long as it's not touching anything but the flat top.


Here's my standard post on choosing a BUIS:

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Are you going to mount a magnified optic? If so, you need to consider whether the BUIS will fit under the scope and mount combo - some mounts (like the Armalite) are very low, and others (like the M1Sales) are quite high.

If it's for a red dot/Eotech style, there's a lot more flexibility.

For a magnified scope, you'll need a flip-up BUIS. For a non magnified optic, you can use a fixed sight as well, which is generally sturdier, but obscures part of your field of view.

A few things to consider when choosing rear flip-up BUIS, depending on if it's going to be a range gun or a SHTF gun:

- Will it be used for precision or long-range shooting? A small aperture is helpful for this. If the use is both close-up and long-range, a dual-aperture sight is useful.
- If it's multi-aperture, which one is deployed when it flips? Some flip with the large aperture deployed, others with the small. If you're not in a hurry, this won't matter, but some people care.
- If multi-aperture, do the apertures deploy in the same plane? Some deploy with an elevation shift to account for the range differences, others use the same zero for both apertures.
- Do you want the windage knob easy to adjust or shielded to prevent accidental adjustments? ARMS are exposed and easy, Troy is shielded.
- Does it have elevation adjustments? Some do (like the Wilson Combat), most don't.
- How easy is it to deploy or adjust if your hands are muddy or gloved? Some, like the ARMS 40, have a latch holding it down that has to be flipped. Others, like the Troy, flip up without unlocking anything.
- Does it latch in the up position, the down position, or both?
- Is it spring loaded, like the Matech or ARMS, or not, like the YHM-9680? Spring loaded will pop back into position if bumped, while non will stay partially deployed if bumped from the unlocked position.
- How protected is it from damage, both down and deployed?
- How robust is the detent mechanism? The Matech will wear over time and become easier to deploy (and eventually won't lock). For many, this doesn't matter, as their BUIS aren't used often.
- How many slots does it cover? This is important if you need to conserve rail space. The Matech and MBUS cover 2, while many others only cover 1.
- Does it get in the way of the charging handle? Some people mount the MBUS a slot ahead of the first slot to avoid this, which uses up even more rail space and changes the MOA/click slightly.
- Is it made of plastic or metal, and is this important to you?

Figure out which of these are important to you and what capabilities you want, and it will narrow down the choices quite a lot.


Here's how to figure out if it will fit under your scope and mount.

- Measure the scope's eyepiece diameter, with flip caps if you're going to use them. Butler Creek usually adds about 0.1" to the diameter. If the scope's going far enough back so the eyepiece isn't over the BUIS, measure the diameter where it is over the BUIS.
- Divide that by 2.
- Subtract that from the centerline height of your mount or rings.
This gives the maximum height BUIS that will fit under that scope/mount combo.

For example, my Leupold VX1 4-12x40 eyepiece diameter is 1.7" with flip caps - divided by 2 gives 0.85". Mounting it in a 1" LaRue LT-104, which has a 1.41" centerline, would leave (1.41-0.85) = 0.56 as the tallest BUIS that would fit. As you can see from the list below, that leaves out many. This is one reason the Troy BUIS is so popular.

Here are some popular BUIS heights:

ARMS 40 - 0.95" folded (mine is 1.00" even)
YHM-9680 - 0.84" to the top of the windage knob, 0.74" to the top of the sight body
Matech - 0.75" folded at the elevation adjustment, off to the side, 0.6" closer to center
MI ERS - 0.75" folded
GG&G MAD - 0.625" folded
Magpul MBUS - 0.625" folded (not verified)
ARMS 40L - 0.61" folded (mine is 0.59")
Troy - 0.460" folded
MI MCTAR-SPLP - .438" folded
YHM QDS - 0.435" folded
KAC 300m - 0.315" folded

[low94noma]

Maxicon, this is great information. I probably would have never even thought about measurements before making a BUIS purchase. Looks like there is a lot more to consider before making a decision. Thanks a bunch for the info, it must have taken awhile to write.