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Posted: 10/14/2004 6:59:24 PM EDT
[Last Edit: strick909]
UPDATED: 8/4/2006

What is BUIS anyway?
BUIS, or Back Up Iron Sights, come in many configurations. The purpose of a BUIS sytem is to give the shooter the ability to accurately aim the rifle if the primary optic fails.

What types are available?
Two types are available, flip up and fixed. It is possible to combine the two systems and use a flip up in the rear and a fixed FSB (front sight base) or vise versa.

What is co-witness?
A: Co-Witness is the ability of your irons to look through your optic (1x - not magnified) - so they both shoot on the same trajectory.  There are two kinds - absolute (both the dot and irons are on the same plan), and offset (where the irons are usually in the lower 1/3 of the optics display).  With co-witnessed sights you can verify the zero of the optic by looking through the irons (the dot should sit on top of the front sight).  However, normally you look over the irons and just use the optic (trust me, you won't notice the iron sights); should the batteries fail your head comes down a fraction of an inch and you're using the iron sights (looking throught the now-dead optic).
(from the Maryland AR15 Shooters FAQ)

What makes folding BUIS so good?
Some shooters like to use a primary optic (such as an Aimpoint or EOTech) with no visual distractions. The folding BUIS sytems would be ideal  for this. Other shooters using magnified optics will require a folding rear sight in order to get proper placement of a scope. Many first responders like a folding front BUIS because it is less likely to get hung on something compared to a fixed FSB.

What makes fixed BUIS so good?
First, it is less expensive. Most rifles will come with iron sights and adding a primary optic to an existing system would be the cheapest way to get set up. Also, if you ever need your BUIS, there is nothing to "flip". They are already in place. That means that the time to transition to BUIS from a disapearing red dot is zero.

If I use a magnified optic, won't the FSB be in the way?
Nope. You won't even see it.

What distance should I zero my BUIS?
50 yard IBZ

Where is the best place to buy my BUIS? Who has the best prices?
Please support the dealers who support this site! Check the Industry Forum for a list of dealers and also check the Equipment Exchange  for other deals on BUIS and optics from dealers and members of AR15.com!! All of the BUIS below have a hot link to the original manufacturer. These links are for informational purposes. Most of the time, an AR15.com dealer will have a better price. However, there are exceptions. Ameetec, Bushmaster, & Cavarms are all AR15.com supporters, so it's ok to order from them.
Talon Arms is my personal dealer of choice...
Talon Arms in the Industry  Forum

What BUIS sytems are available?

40L SP (same plane aperture)

40A2 (2.0 oz)

Ameetec Arms
Front Folding

Rear Folding

Bushmaster BMAS
BMAS fixed rear (3.2 oz)

BMAS flip up rear (1.5oz)

BMAS Flip up front

BMAS flip up front rail mount

Cavalry Arms
Cavarms fixed rear

Fixed rear

Mangonel Front Flip Up Sight

Mangonel Rear Flip Up Sight

Detachable Front Sight

MAD flip up rear

A2 flip up

Tactical Modular flip up front

Flip up front for dovetailed gas blocks

Knight's Armament (no link available)
Rear Folding 300 Meter Sight

600 Meter Folding Rear Sight (2.25oz)

Folding Front Sight for RAS

LaRue Tactical
Fixed rear sight (QD) (3.0oz)

Les Baer
Front flip up w/gas block

Fixed rear sight

Tactical Front Sight Assembly

Matech  No link
Folding rear
no photo

Midwest Industries
Folding Rear

Front flip up gas block

Rail mounted front sight

Samson Mfg. Quick Flip Sights

Barrel mounted Quick Flip Sight / Gas Block

Rail Mounted Quick Flip Sight

Weaver gas block mounted Quick Flip Sight

Troy Industries
Flip up Rear (1.9oz)

Flip up front Rail mount (2.2oz)

Wilson Combat
Flip-Up Rear Sight

Yankee Hill Machine
Gas Block Front Flip Sight

Forearm Front Flip Sight

Solid Front Sight

Front Sight Gas Block

Front Sight Tower

Flip Rear Site

Solid Rear Sight
Link Posted: 10/14/2004 9:07:42 PM EDT
Absolutely needs to be a sticky
Link Posted: 10/15/2004 3:33:33 PM EDT
BTT for comments anyone?
Link Posted: 10/15/2004 4:03:47 PM EDT
This should be tacked.  Good info.
Link Posted: 10/15/2004 7:36:58 PM EDT
[Last Edit: Perfectforce] [#4]
I would really like to see some opinions of people that have used or are using any of these BUIS.
Link Posted: 10/15/2004 7:41:05 PM EDT
[Last Edit: norman74] [#5]
That's the only two rail-mounted flip fronts?  Troy and YHM/BMAS?

Oh, and you left out the Cavarms rear BUIS

Knight's 600 meter rear

and 300 meter rear

and folding rail mount front

and SR25 flip front

and the Wilson Combat flip up rear
Link Posted: 10/15/2004 7:47:32 PM EDT

Originally Posted By Perfectforce:
I would really like to see some opinions of people that have used or are using any of these BUIS.

That's why I posted this. I was hoping that we could start a central BUIS discussion thread instead of  reading 50 seperate threads on each individual BUIS.

FWIW, I use the ARMS 40A. It's very solid and combat proven. You can find them in the EE all the time for less than $100.
I am looking to pick up a new BUIS for a scoped upper. I really like what I am hearing about the ARMS 40L and the Troy folder. Hopefully we will get some reviews soon.
Link Posted: 10/15/2004 7:50:38 PM EDT
Thank you very much!
I forgot all about the KAC sights. The others I have never seen.
Link Posted: 10/15/2004 9:35:32 PM EDT
This rates a permanent tack.

Dave S

BTW, thanx.
Link Posted: 10/15/2004 9:59:17 PM EDT
Some good info in this thread. Hesitate to say to tack since 1. There are a lot of stickys alreadys and 2. People refuse to read them and ask the same ass questions anyway. GJ though.
Link Posted: 10/15/2004 11:42:42 PM EDT
[Last Edit: strick909] [#10]
DPMS, LMT and Les Baer added
Link Posted: 10/16/2004 4:49:35 PM EDT
I think it needs to be tacked. All the other stickies have to do with optics. Starting just 1 for BUIS is beneficial.
Link Posted: 10/16/2004 4:53:32 PM EDT
[Last Edit: NYPatriot] [#12]
Nice job Strick909!

You might want to throw this into the mix as well: CNC Gunsmithing A1 BUIS
Link Posted: 10/16/2004 5:29:17 PM EDT
I agree this needs to be tacked to this page.  

Too much good info to just pass up.
Link Posted: 10/16/2004 5:42:22 PM EDT
Good info.  Now, just add the weights for each, and it will be tack worthy.
Link Posted: 10/18/2004 7:39:35 PM EDT
Bump for all the BUIS questions lately
Link Posted: 10/18/2004 10:58:04 PM EDT
Great thread!!!!!!
Link Posted: 10/19/2004 1:36:11 AM EDT
Link Posted: 10/19/2004 9:26:36 AM EDT
+1 for Tagged.
Link Posted: 10/19/2004 9:53:19 AM EDT
Thanks for the info Good Job. Answers a pile of questions I had about sight options. Can they put this in the build it yourself section for further reference?
Link Posted: 10/19/2004 10:46:27 AM EDT
Link Posted: 10/19/2004 11:10:03 AM EDT
Great Job !!! - BTW I think you should add the Cav-Arms A1 style fixed rear sight.
Link Posted: 10/19/2004 1:57:31 PM EDT

Originally Posted By Corporal_Chaos:
Good info.  Now, just add the weights for each, and it will be tack worthy.

If someone knows the weights of each, I will add them. And does anyone have a link to Knight's?

I did not list MSRP because all of the links are hot and you can get that info from the manufacturer anyway. But, if you guys want it, I will list it. Is there anything else I am missing?
(BTW, I did not list the A1 hot-linked because it is not yet a regular production sight.)

Knights (via Impact Guns), Cavarms, and Wilson Combat added to the first post.
Link Posted: 10/19/2004 3:05:49 PM EDT
Great info!  Someone tack this post already!!!
Link Posted: 10/19/2004 3:28:12 PM EDT

Good info.  Now, just add the weights for each, .

I'll tell you what I'll share the info I have if you get the weights on the others:

From the 'Chart of AR-15 Part and Assembly Weights' from The Maryland AR-15 Shooters Site:
(weight is in US ounces).

Troy Front Flip Up Sight 2.2
Troy Flip Up Rear BUIS 1.9
ARMS #40 BUIS 2.0
LaRue BUIS 3.0
KAC 600M BUIS 2.25
Armalite "Chopped Carry Handle" sight 4.9
Detachable Carry Handle (A2 sights) 9.6
Link Posted: 10/19/2004 3:56:46 PM EDT
Tag..good info here
Link Posted: 10/19/2004 4:24:52 PM EDT
Thanks forrest, I will post more weights as I get them.
Link Posted: 10/19/2004 4:42:43 PM EDT
[Last Edit: ipsilateral_7] [#27]
very cool, the only buis I don't see on the list that I know of is the Matech buis being used by the army some, I can not find the pic at the moment thought, the thread that they were discussed in is over 3 months old,

there were nice pics at this thread
Link Posted: 10/19/2004 5:45:30 PM EDT

Originally Posted By ipsilateral_7:
very cool, the only buis I don't see on the list that I know of is the Matech buis being used by the army some, I can not find the pic at the moment thought, the thread that they were discussed in is over 3 months old,

there were nice pics at this thread

That link is dead.
Link Posted: 10/19/2004 7:40:30 PM EDT
To quote the Guiness commercial,


Good work, Strick.
Link Posted: 10/20/2004 11:39:12 AM EDT
In addition to the weights, I think it would be great if everyone that uses the various sights could post folded heights.  Might save folks trouble, time, and money when selecting a sight to fit under an optic.  Great post, by the way!
Link Posted: 10/20/2004 12:51:03 PM EDT
[Last Edit: TheRicker] [#31]
Link Posted: 10/20/2004 1:54:29 PM EDT

Originally Posted By TheRicker:
Still updating, will post chages tomorrow-ish.

This is awesome! I will add this to the first page/first post when you update. That is, if it is ok with you. (stuff like this is why I love ADCO )
Link Posted: 10/20/2004 2:24:06 PM EDT
[Last Edit: TheRicker] [#33]
Link Posted: 10/20/2004 4:47:06 PM EDT

Originally Posted By TheRicker:
Still updating, will post changes as I get them. Need weights, heights, etc.


Link Posted: 10/20/2004 5:07:10 PM EDT
Link Posted: 10/20/2004 7:15:46 PM EDT
This should be tacked, don't you all think?

Link Posted: 10/21/2004 12:06:13 AM EDT
Updated and tack worthy I hope.
TheRicker, I just hot linked the gif. As you update, it should be seen in my first post unless you move it. PM me if you do and I will fix the link. Great job BTW!
Link Posted: 10/21/2004 8:01:57 AM EDT
Link Posted: 10/21/2004 10:39:59 AM EDT

And you know, if a sticky doesn't happen, we can always make it into a web page and update it as needed.

strick909 - Nice Job!
Link Posted: 10/22/2004 2:58:59 PM EDT
Man, I sure wish this was a sticky before I spent valuable reading other's useless postings on BUIS 's . Many of the other postings were nothing more than Ford vs. Chev type banter. I just want the facts...man without having to read everybody's  sales pitch, catalog description and biased testimonials.  This is by far the most definitive info with pictures  on the subject. This post is definitely a time saver and could lead to reducing those same old questions being asked over and over again. Of course, there are those who no matter what just want to ask questions with out the  effort to research.

Great job strick909 !!
Link Posted: 10/22/2004 10:08:29 PM EDT
I plan on getting a Rock River CAR A4 one of these days with the gas block instead of the standard front sight.  So as a general rule do most of you guys pair up the front & rear flip-up BUIS by manufacturer - for example do you stay with both YHM, Troy or GGG for front/back or does it make no difference?  Is there an advantage to stay with one manufacturer for both or not?  

Also, since ARMS does not make a front flip-up, which front flip-up BUIS would match up with a ARMS 40L on a rifle like the CAR A4?  Thanks, Mike.
Link Posted: 10/23/2004 10:36:08 AM EDT
I have a 40% off coupon for Wilson Combat. Does anyone have any experience with the Wilson BUIS?
Thanks for any info.
Link Posted: 10/23/2004 11:44:18 AM EDT
Mike 48,
You can mix and match BUIS all you want. Make sure that the front flip you buy is made to mount on a gas block and not the front rail. The GG&G is very well made. The BMAS and YHM are both made by YHM and a good choice as well. Both should work with the ARMS with no problems.
The Troy Ind. front is made to mount on the FF rail not the gas block.

I have never seen the Wilson in person, but for 40% off, it seems worth the risk to me.
Link Posted: 10/25/2004 10:56:20 AM EDT
Link Posted: 10/25/2004 11:11:03 AM EDT
All mil-spec rear sights must be at a certain ht. Front sights from after market makers should be mostly OK, but the rear sight is the governing factor if it is mil-spec. Mil-spec means that the goverment have bought them to work with the std. ht. of the issue barrel mounted weapons that Colt and FN make.
Link Posted: 10/25/2004 2:37:13 PM EDT
[Last Edit: jar3ds] [#46]
uh... please tack this forum
Link Posted: 10/25/2004 2:52:09 PM EDT
Link Posted: 10/25/2004 3:33:45 PM EDT

Nicely done.
Link Posted: 10/25/2004 3:34:31 PM EDT
Tag. Wow, great info here. Thanks alot for taking the time to compile all this. Makes my gear whoring easier.
Link Posted: 10/25/2004 4:28:38 PM EDT
In the interest of correctness... the flip front listed as "Les Baer" is actually built by Young Manufacturing.  


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