Hello.After much reading and pondering of post on AR-15.com I've purchased a Bushmaster M-4 lightweight dissapator A-3 upper assembly. I intend to use a Eotech holo sight on it.Therefore per what I've read on this board I ordered a Arms 40 buis for use with the holosight. I have a question as to mounting the buis. 1Do I need to use a loctite product on the buis mounting screw? and 2 Can I mount the arms 40 buis before I mount the eotech or does the eotech have to slide on the A-3 upper rail  first? I would greatly appreciate any assistance as I'm not sure since I do not have the holo sight yet. Thanks.

Ive never had an ARMS 40 work lose, so Ive never used loc-tite.  Own an Aimpoint not an Eotech, so I'll wait for them to answer your question on that.

The optic should clip straight on, unless its some kind of weird mounting system. No, you shouldnt have to use loctite. I never had to with my ASA or Knights sights.

SEMI15,

You don't need Loctite to mount the ARMS #40, and the ARMS can be mounted on the flattop before the EOTech (the EOTech attaches from above, no need to slide it on.)

See my photos in this thread:

[url]http://ar15.com/forums/topic.html?b=3&f=18&t=159392[/url]

HTH.

when mounting the eotech you loosen the mounting screw which loosens a section of metal that clamps to the rail.

i just go the same two items for my a3.

In fact here is another tip, mount and zero the BUIS first.  and zero it correctly, and then put the eotech on and zero that.

doing the buis first will keep you from playing with the new electronic gizmo, like i did...
i like shiny things, too.

Thank you all for sharing your knowledge. I now know how to procede. Mount the buis,no loctite,zero buis,then worry about the holosight.

Hopefully this isn't TOO off-topic...I will soon be getting the EoTech and ARMS #40 to go on my A3 upper.  Can the #40 BUIS be stored in the "down" position so that when it is flipped up, the small aperature is ready?  GMan552, that looks like a sweet set-up...  

You COULD use loctite on the screws if you wanted, and if i were actually fighting with the rifle, i certainly would.

But for just banging around at the range and courses, i've never had the BUIS loosen up, so i just screw it on tight.

#40 only stores with the large aperture in the ready position.

dk_erickson, thanks for the kind words, I'm very happy with the setup.

The front sight post and ARMS #40 do co-witness in the center of the EOTech field of view, but it doesn't interfere with the use of the EOTech reticle.

I might suggest zeroing the BUIS *with* the EOTech mounted, as there have been reports that the refraction from the optical sights (EOTech, Aimpoint, etc.) can change the BUIS point of impact, when compared to looking through the BUIS without the optics in between.  

If I need the BUIS because the batteries or reticle are dead or the lens is broken, I won't have time to remove the optical sight, I'll just flip up the ARMS and look through the optical sight (hopefully it won't be so smashed I can't see anything through it).

You might consder the Santose improved battlesight zero (IBZ) for the irons (look at the bottom of the page):

[url]http://groups.msn.com/TheMarylandAR15ShootersSite/improvedbattlesightzero.msnw[/url]