I can't decide between the ARMS 40 and the LMT BUIS. What do you think? I plan on getting an Aimpoint or an EOTech.

IMHO-ARMS #40a2.

Flip up BUIS are more versatile than Fixed.

It's kinda of annoying when you have a permanent fixed peep in the way of your primary optic.

A fixed optic blocks a full view and can snag on shit.

It makes quick snap shooting a pain and defeats the purpose of a red dot/reflex sight.

It's so much more convenient to flip it down when not in use or flip it up to check your zero/cowitnessing if your primary optic is off.

Some people like the fixed, however i can't seem to see why.

Flip up BUIS!!!

Personally speaking here folks....

I see no point in buying an optic and then having the view partially obscured by a fixed sight.

Yep, Aimpoint go fixed (cut down CH to save $$ for more stuffage), Eotech #40.

Gents,

The new CQB upper from Crane comes with a fixed LMT BUIS.  That is the result of lots of R&D that real operators were involved in.  

Ive been a flip up person myself, and that works fine for a day at the range, but I have seen flip ups break in hard use.

I still use a flip up on my SPR, but for a hard use gun a fixed is the way to go.  I switched from a KAC 300m BUIS to a Cut Carry handle.  If you have your optic mounted forward then the BUIS never comes into your field of view.  

The military have been buying a lot of flip up sights in a ratio of aprox 1,000 to 1 of the non folders. The #40 is very very rugged and locks down out of the way, but when it's deployed it goes automatically back into battery if hit by accident.
Jack

A sight you have to flip will cost you [i]points[/i] in a gun game.  Imagine what it can cost when the targets have the audacity to shoot back!

If you can fit a fixed rear sight I strongly recommend it.  Bus, if you can't, the ARMS #40 is a good choice.

-- Chuck

Go with ARMS #40.

It also depends on the optic.  I actually don't mind a EOTech with a fixed BUIS, but if you'r going to mount an ACOG or an AN-PVS 14, then you defintely need a flip down unit with a low enough profile to fit under the optics.  If you are just employing a forward mounted red dot or holosight, then it depends on the position of the otic and what your personal taste is.  Myself, I prefer fixed sights if at all possible.

First off, I have an ARMS #40 and I love it.  I purchased it based on the recommendations of countless members and because 1) I didn't want to look at a sight I wasn't using and 2) I wanted the ability to upgrade to more equipment.  I'm now using an Aimpoint and a SIR with it, so I'm extremely happy with my BUIS choice.  In retrospect, if had wanted to use a FF RAS or RAS II, I'd be wishing I had the LMT right now.  When I shoot with my #40 up, I NEVER notice it until I want to.  I've become fond of having it up with the small aperture, as I seem to shoot better at a distance using the irons and the Aimpoint simultaneously (perhaps I'm just weird).  Basically, it depends on what your end goal is.  If fixed irons aren't going to get in the way, go with fixed.  (I've never actually shot with an EOTech, but from looking at it I'd prefer the #40 with it because the lower height.)  If you want the option to get magnified optics or a SIR, get the #40.  

I have both an ARMS #40 and the LMT.

My ARMS #40 sits behind an Aimpoint on my M4 clone and it works great.

My LMT is currently on a light weight Dissipator and has no optics in front of it. It will be behind an Aimpoint soon.

I have run both sights behind the Aimpoint and both work great. The LMT does not obstruct my view and I have never had it get snagged on anything. I have run two classes now using it, and it is fast to acquire.

If you're running an ACOG or some other scope, then I vote for the ARMS #40. If you want to mount a SIR then you must run an ARMS #40.

But if you're going to run an Aimpoint on a flat-top receiver or on a forward rail of some kind then the LMT gets my vote. It is an incredible sight. It will always be there. It won't fall down, it won't be down when you need it, and I really doubt you'll ever be able to break it.

Wes,
   So your saying the Aimpoint dot sits above the LMT and I can look at the dot without looking through the irons.

The LMT will co-witness with the Aimpoint. Just like an ARMS #40.

I think what he's saying is - if you focus on the dot the sights "disappear" and don't distract you. If you decide to line up with the Irons, you're already there, and by just changing your focus you then see the iron sights.

At least that's how it works for me.

Chuck                                     Whats nice about the #40 is that you can lock it down, or leave it up if you wish and it won't fall down if hit by accident do to the tortion spring, opposed to detents that fail if hit.
Jack