Regarding my 6920 flat top M4..... Why would you bother buying an ARMS 40A2 standard sight, when for about the same price you can get the dual aperature 40 stand alone sight?  I'm not familiar with the aperature offered in each of these two different sights, except what I read on the ARMs web site which doesn't explain the direct comparison.  Am I missing something here?Is the aperature that different between the two that I might consider choosing the standard over the A2 sight?

I've already bought an Eotech.  I'll likely buy a LaRue base to keep the front sight out of the Eotech's red circle.

The standard 40 is slightly shorter than a 40A.  This is because the top of the small aperature is ground off.  Making it fit below some optics.  Both have dual aperatures, at least my 40 and 40A do.

GotM4,
I was confused.  The A2 is the standard sight.  The ARMS 40 Stand Alone sight is the extended range sight. The top of the one aperature is ground down, but the other aperature isn't? Do you have a preference of one sight over the other?

Quoted: GotM4, I was confused.  The A2 is the standard sight.  The ARMS 40 Stand Alone sight is the extended range sight. The top of the one aperature is ground down, but the other aperature isn't? Do you have a preference of one sight over the other?

I like the 40A better.  It's the one not ground down.  I get a better sight picture with it.  The ground one plays tricks on my eyes.  I don't have clearance problems with either as both are behind EoTechs.

Gotm4,
Which ARMS aperature is closest to the original aperature on my Colt m4 rifle? The ARMS A2?

With the notch and ground down small aperature the peep sight looks like a U instead of an O when your eye fuzzes out and the rear peep is out of focus on the standard 40.

Devl,

Now which sight? ....So you too are suggesting a preference for the 40A2 (not the #40).

I wish ARMS would have used a different prefix when describing these two sights. It would have been less confusing if they called one of these sights the "40" and the other one the "50" or a "Betty Sue" or anything else.

The 40 has a special aperature.  The 40 A2 has a standard military A2 aperature.  Its real easy to remember.  A2 = A2 and the other is not the A2.  I prefer the A2 aperature... but it wont fit under a TA31/TA01.

My suggestion is to just wait till the dual aperature Troy BUIS comes out and see if that is all its cracked up to be.

Devl,
When it comes down to it,  they're both listed as a "40"  To use the word "standard" can be misconstrued for either sight as "standard" is a generic term. When these sights are being talked about off the cuff, back and forth, you almost have to say "A2" or "non-A2" to clearly differentiate which one is in topic.

As  far as the TROY goes......if I'm a nimrod and don't know my butt to my elbow about any of these sights and have never owned one, it's less appealing for me to go out on a limb and buy a TROY and "See if it's everything it's cracked up to be". The ARMS is tried and true enough for me. I guess when I have played with this stuff for years (like I observe some of you guys have), and I have a drawer full of duplicate parts, I can then start trying different things to make life more interesting. Right now I just want stuff that I know has worked in Iraq.

Thanks for the help.

The 40 is notorious for for working its way loose if not locktited properly.  Even then I have heard of people having it come loose over time.  Its slower to deploy than the Troy unit.  Its heavier than the Troy unit.  If you want what has worked well in Iraq none of these units get used so there is little to credit there.  If mil spec is your deal go with the KAC 300m BUIS (thats the primary BUIS used by our military) as its about the lightest and simplest out there but has no ability to lock in th up position and has a rubber insert for the large aperature to make it a small aperature. They just sit behind the primary optic doing nothing so noone really has it "work for them" in the field.  

To me there is exactly ONE reason to get an ARMS 40.  That reason is you intend to get the 19S and mount a TA01/TA31 on it and want to get the optic an extra notch further to the rear on your upper reciever since thats the only combo that will allow that.  If you intend to use a LaRue mount or another optic the 40 is just extra weight and slower to deploy and less stable in the up position and more likely to work its way loose compared to a Troy BUIS.  The only thing you need to see in order  to see if the Troy is "all its cracked up to be" is:

1.  Does it default deploy to the large aperature
2.  Will it fit under a TA31/TA01 scope in dual aperature form

If it does both it is clearly superior to the 40 and 40A2 in every way.  I have also heard that a large number of Troy units were ordered by the military... dont know if thats true or not and dont care really.

Devl,
I already have an Eotech I plan to mount on the flat top M4. I would like to buy a LaRue mount for it, as I am told that without raising the Eotech, the ARM40A2 will have its sight picture in the Eotechs outer red circle. Is this correct? If so would the TROY dimensions serve well?

Perhaps, for my purposes the TROY would work just as well then, being you have so much confidence in it. (and more so then the ARMSA2)

The biggest problem I am discovering, is finding anybody that has stuff in stock! I hope while I wait, we don't get attacked before election day. My Eotech is in it's box, my 223 ammo in the closet, and my 6920 in the bag with a tag over its barrel!

Quoted: The 40 is notorious for for working its way loose if not locktited properly.  Even then I have heard of people having it come loose over time.  Its slower to deploy than the Troy unit.

I guess some people need to get off their lazy asses and check their gear before using it.  I used Loctie on my ARMS #40a and after close to 8000 rounds it has not loosened up one bit.  

With that being said anything mounted by man can come loose so check your gear and re-apply Loctite as needed.  Also, anyone that doesn't locktite their ARMS 40 shouldn't blame the BUIS when it comes loose since it's an obvious operator issue.

Also how is the ARMS 40 slower to deploy than the Troy BUIS?  All you do is pull back the retaining latch and it springs up.  I've used both and I don't see that pushing up the Troy BUIS is any faster than unlatching the ARMS 40.   Even though the ARMS 40 is no longer the latest in Gucci Gear it still does what needs to do very well.

BTW, I also like the Troy BUIS and will probably use one on my next build but you can bet your ass I'll be using Loctite on it too.


VaniB,

You may want to try using the EOTech on the flat top before spending the money on the Larue mount. Many people including myself don't find the front sight to be an issue when properly using the EOTech.  

The 40 requires you to reach up then pull back on the reatining bar (very small) and if you try to do it to fast by hacking at it you can not get the bar to deploy sometimes.  The Troy is simple to press forward in one motion and does not have a small part to manipulate with gloves on like the 40.  The difference is small but it exists.  I agree you should lock tite all BUIS.  I simply find the Troy easier to manipulate.

The 40 series of fold down rear sights all have the (FAST and EASY) to rease lever.  The military customers want a sight that will go back into position (spring loaded) if hit, and lock down instead of accidently being deployed. Others do deploy by a simple bush, like from a branch when they do not want them to, as a snag can ruin a sight. #40's are in service in the thousands in Iraq, etc. #40's were chosen for the SPR sniper rifle and many M4's by the SPEC OPS and other units, because they are reliable. The only (notorious) thing is the (loosening) of (facts) by by some very few, who didn't know enough to use the loc-tight that ARMS supply with each sight.
Good shootin, Jack

Jack,
That's some interesting facts to know.

So uhhhhh.....for my Eotech on the 6920 M4, which one would be your choice for me? The #40 or #40A2?

Since I don't know enough about these sights, and haven't had a chance to ever use them to make my own qualified decision, I'm trying to build a consensus with you guys that know the differences between the two. I was going to go with the 40A2 which seems most guy's favorite ARMS sight

DevL,

Okay, I'll give the Troy BUIS a .25 second advantage in deployment speed.

VaniB,

I would choose the ARMS 40a because, IMHO,  the Horizon cut makes the small aperture virtually useless.  I have a EOTech 552 and I use the ARMS 40a(full small aperture) as my BUIS.

Edited for typos...

Quoted: I would choose the ARMS 40a because, IMHO,  the Horizon cut makes the small aperture virtually useless.  I have a EOTech 552 and my and I use the ARMS 40a(full small aperture) as my BUIS.

+1 That is my rig as well. The A2 ap is the way to go.

Yojimbo and Strick909,

Ah, now I feel like I'm finally building a solid consensus, and can choose and buy the ARMS 40A2

Do you two guys agree with another post here that I shouldn't find the sight picture blocked that bad when viewing through my Eotech 512? There's no sence in me going to the range and sighting-in the new Eotech only to find I have to take it all apart later, and order an elevating mount. ( like the LaRue base.)  I've heard it said that the LaRue base will raise the sight picture and keep the obstruction image in the lower third of the window, and out of the outer red circle of the Eotech .

So, should I:

Be done with it and buy the LaRue base before going to the range? Or try out the Eotech first on the flat top receiver with a new 40A2 BUIS  first which I may like just as is?

I can't speak for strick99 but I have no problems using the EOTech without the Larue mount.  All of us EOTech users seemed to do just fine before the Larue mount came out so I would recommend trying it first before spending the extra cash on a mount that you may or may not need.  JMHO...

When you go to sight in your EOTech make sure keep the following things in mind:

1. Keep both eyes open.  When you keep both eyes open the front sight base literally disappears.
2. Focus on the target not the reticle.
3. The 65 MOA is not for precise aiming, it is strictly for CQB, so think of it as a ghost ring. Place the 65 MOA ring COM and press the trigger as needed.
4. The 1 MOA dot will be sharp and clear, use it when precise aiming is needed.

The IBZ or 50 yard zero works best for the non-magnified red dot optics.

OK, well, after searching and searching I can't seem to find an exact answer for my question anywhere.  I've got a TA31A mounted using a TA51 on a flattop with a KAC RAS II and want to add a BUIS.  I'm looking at the ARMS 40, 40A2, and 40L and my initial preference is the 40A2 (regular height, A2 aperture) but I'm not convinced it'll fit under my ACOG.  Since I've got the RAS II the ACOG is mounted pretty far back on the flattop and there are two slots remaining behind the TA51 before the end of the upper.

Anyone have this combination and know if it works/doesn't work?  Any pics?

Quoted: I can't speak for strick909 but I have no problems using the EOTech without the Larue mount.  All of us EOTech users seemed to do just fine before the Larue mount came out so I would recommend trying it first before spending the extra cash on a mount that you may or may not need.  JMHO... When you go to sight in your EOTech make sure keep the following things in mind: 1. Keep both eyes open.  When you keep both eyes open the front sight base literally disappears. 2. Focus on the target not the reticle. 3. The 65 MOA is not for precise aiming, it is strictly for CQB, so think of it as a ghost ring. Place the 65 MOA ring COM and press the trigger as needed. 4. The 1 MOA dot will be sharp and clear, use it when precise aiming is needed. The IBZ or 50 yard zero works best for the non-magnified red dot optics.

I agree. try the EOTech mounted directly to the flat top before you spend extra money on something you don't  need. With that said, you may like the many LaRue features and decide to buy one later. I don't want one because I like the true co-witness of the flat top mounted optic. I like the 1MOA dot on top of my front sight post , not above it. I like the ARMS 40A peep sight over the 40's half peep as well. Follow all four suggestions above and set your irons and optic for the 50 yard zero and you are good to go.

VaniB, I also chose the 40A2 over the 40.  When I asked around most folks recommended ARMS.  Of the ones that had the 40, some said their only regret was not getting the 40A2.

Be wary of folks that push the latest and gretest gadgets, some just have to have the latest thing to grace the range.

OK, what's the deal with the 40L?  I don't see many people talking about it.  Doesn't it put a rear peep flip (small aperature and large, like standard A2) in the same place as a standard 40 when it's deployed?

Or does it have a cropped aperature like one of the other 40's?

I intend to put one behind an Eotech, and just want something there that will zero the gun at 100m if I take the Eotech off for whatever reason.

Thanks,

Ted

Eotech and ARMS 40, eotech mounted right on flattop:


I prefer the eotech to cowitness with the irons, its 1 moa dot doesn't make my shooting any less precise than without it, and if it bothers you when sighting using the irons, it has "off" capability!