Scope and BUIS ?

[Sendit]

So i need some input i recently mounted a leupold 4.5-14-40 with a larue 104 mount on my larue 20" upper. Im trying to figure out who makes the lowest profile front and rear irons its really hard to tell from all the adds

[jmf_tracy]

troy BUIS

[high_revs]

i thought midwest industries made one lower. it's the pricier of the rear folding sight. i got one. was about $120 or so. it did "seem" lower than the troy folding battlesight.

[J_Rock]

BUIS CHART

http://www.angelfire.com/apes/hit28/buischart.htm

[sholling]

I like Troy because they do set so low.

[maxicon]

Here's my standard post on choosing a BUIS, including how to know whether it will fit under your scope/mount combo. For general purpose use, it's hard to go wrong with the Troy, if your budget allows.

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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.
- If multi-aperture, how hard are the apertures to switch? It it likely to get bumped where it's between 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, KAC 600M, and Matech), 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. Some BUIS have a higher knob or adjustment on the side, and some scopes will clear at the center, but hit off to the side. It's hard to tell if this will be a problem without trying it out.

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
ARMS 40L - 0.61" folded (mine is 0.59")
Troy - 0.460" folded
MI MCTAR-SPLP - 0.438" folded
YHM QDS - 0.435" folded
KAC 300m - 0.315" folded