I recently purchased the S.I.R. system and I'm a little disappointed with the short rails.The bottom rail is too short to mount my M3 light and my vertical foregrip.Does A.R.M.S. sell a longer rail for the S.I.R.? I can't find it on their site.I was also wondering if the S.I.R. system had gotten a military contract, and if it has been deployed in Operation Enduring Freedom. A reply on this would be greatly appreciated.     Thanks, SOLDIER1

From what i heard, SIR is getting rave review from the field.  

Call ARMS for additional rails.  You can add a short side rail to the bottom to complement the longer rail (in theory).  Maybe this will work for you.

Call George at ARMS, he will be able to help you.

I don't know what you want to put on the short side rails that would be practical, since any device would get in the way of the hand hold on any weapon. I do know that the two short rails combined are longer than the long rail, and will go on the bottom. the bottom rail can also go in the side track. They definitely are issued to troops in nasty places and are well liked for the versatility of placing equipment and cool running. You need to call the maker via their web sight, armsmounts.com
Good shootin,Jack

Are you using either of the side rails? If not, just use two side rails on bottom. One for the M3, one for the grip. If you are using a side rail, contact ARMS and get how ever many rails you may need. I have found ARMS to be quick to respond to customer emails and needs. I've always considered the fact that the SIR allows you to utilize as many or as few rails the user requires as one of the great advantages of the SIR. Good luck and let us know how it goes!

A long and short rail will NOT fit together on the bottom of the handguard.

Two short rails on the bottom just wasn't cutting it for me, so this is how I solved the problem:

1) Mount a short rail to the bottom/front, with the mounting screw to the rear, and a short portion of the rail is protruding forward.  You'll mount your light to this.

2) Take the long #3 rail and place it as if you're going to attach it to the bottom, behind the short rail.  Notice that the end with the "#3", from its mounting lug forward, makes it too long to fit.

3) Using a hacksaw, cut this excess railing off the #3 rail so it WILL fit behind the short rail.  Use fine sandpaper to clean up the cut, and touch up the cut surface with a marker, aluminum touch-up, etc.  The touch-up is not necessary though, because the fit between the two rails is so close that you won't see the shiny aluminum.

Now the #3 rail will fit perfectly behind the short rail, making one continuous rail.  Also, the grip is now attaching to the #3 rail, which is secured by TWO screws to the handguard, as opposed to one, if you had attached it to the other short rail as mentioned in the other posts.

I did this on my SIR because I really didn't have a need for the #3 rail, and an additional short rail costs $34.20.

I am very happy with it, and will post a pic here once I get home from work.


Chris

Thanks for your input guys. I have no idea why I did'nt think of these things.I've already put the short rails on the bottom and this works much better.The reason I was asking about the S.I.R. being in service in Afganistan was because I've been watching CNN,looking through Soldier Of Fortune magazine,and although I've read that it was in service, all I ever see is the troops with the R.A.S. & R.I.S. on the M4.I own a R.A.S., and think its a great rail system, but I prefer the S.I.R..Again thanks for your help....    soldier1  p.s. I'd also like to see that pic.

I had the same problem so I just attached an extended rail cover from GGG Az.  That will mount right over the short rail on the bottom and will allow mounting alot more stuff.

Any (rail) that sticks out beyond any hand guard is going to be a brush catcher.
Good Shootin, Jack

Quoted: Any (rail) that sticks out beyond any hand guard is going to be a brush catcher. Good Shootin, Jack

In my case, the rail, by itself, extends past the handguard about 1/4", but then there's about 2 1/2" of Surefire 6P out in front of that when I'm using it for its intended purpose.

It works just fine for me.


Chris

0603
Yep, A 1/4 inch isn't going to be a problem in most cases, I was referring to double or more than that. The surefire is a good set up. Personably, I like any grip back mid way on the lower hand guard, but that also depends on a lot of various other devices to be mounted, size of shooter, stock extended, full open or a mid lock.
Good shootin, Jack

ARMS does NOT sell any rail lengths other than the "short" and "long".  I was in close to the same situation as you and had asked them.

Here's one pic that I have on my home computer of the #3 rail modification that I mentioned previously:



The grip is mounted to the long, #3 rail.  Underneath the rear of the grip is the end screw for the rail, and the back end of the rail lines up with the back edge of the grip.  In front of the grip is the second rail screw, and two notches in front of that forward screw is the end of the rail.

The KAC light mount is on the short rail.  Just behind where it's mounted to the rail is the mounting screw for that rail.

You should now have an idea of the break between the two rails.

This setup allows me much more flexibility with grip position that having the two short rails, plus like I mentioned above, the grip is attached to a rail secured with TWO screws.  VERY solid.

Here's a good pic with the grip off.



I also wanted to mention that I was looking at another short rail to mount on this right side, 3 o'clock position, with another sling swivel like the one that came with the SIR.  I wasn't going to mount anything on the rail other than the swivel, and I just wanted its mounting screw to further secure the lower handguard to the upper portion.

After finding out that a short rail is $34 and the sling swivel is $22 (this is the military price that ARMS quoted me after faxing in a copy of my military ID card), I used instead a 10-32x7/8" 115 QD dome machine screw with two black washers to do the task.  

The threading matched those on the SIR, and the screw was $2.  

You know, you can't get better customer service than ARMS has, and the quality and reputation of their product is well known here, but $22 (and military price at that!) for that screw-in sling swivel?!

You've GOT to be kidding me!


Chris

Chris,                                       We just got some of the new Arms #4 rails that go only on the bottom of the SIR's. They are long enough to accommodate what you show, plus they can be end for ended to give an extra half inch if rail in either direction. The sling swivel solution you did sure wouldn't pass for general issue as it will eat up and wear the material that it will be rubbing against when under constant minor rotation.                                       The Arms swivel is stainless steel, has a housing that is espec. made to counter wear and has a detent that keeps it from accidently unwinding if the sling is not in use. You can also store the Arms swivel inside the the bottom rear of the handguard if need be. You don't get all that for $2. bucks and you didn't count the loop you screwed into place from some other source, and no costs to meet gov't inspection approval. Lets be fair and not mix apples and oranges. The companies that build our defense systems have costs that allow them to answer the phone, have it in stock, heat/cool the building, pay the wages, pay their taxes, package the items, buy the fax and computers, do the engineering, and all the other little things that we all sometimes forget, but could you do that for two bucks? None of the gov't contractors are able to compete with do it your selfers and a hardware store with no spec's., rules, or special toleranced dimensions for our benefit in the field. If they were intending to get rich on 22 bucks, they would have made a spec. thread that we couldn't get in a hardware store. If the home made solution fails, will the hardware store replace it for you at no charge, fat chance. Food for thought.
Good Shootin, Jack

Quoted: Chris,                                       We just got some of the new Arms #4 rails that go only on the bottom of the SIR's. They are long enough to accommodate what you show, plus they can be end for ended to give an extra half inch if rail in either direction.

Good news Jack, and thanks for the heads-up.

The sling swivel solution you did sure wouldn't pass for general issue as it will eat up and wear the material that it will be rubbing against when under constant minor rotation.

I'm tracking with you Jack, believe me.

All I wanted was to have a short rail on that side just to further secure the handguard, and an additional sling swivel for G.P., but not for $57.  

I've already paid $400+$100 for my SIR, and that's enough for now.

I did realize the design of the sling swivel, and how it's attached to the rail and NOT directly to the SIR itself, which is why I do NOT use the QD stud to attach a swivel to.  I only use it as a screw only, an additional method like I just mentioned to secure the lower handguard in place since I don't have a short rail to go on that side.

I have this SIR on a range rifle, that I'm not going to take to the field.  I have an issue M4 for that.

The Arms swivel is stainless steel, has a housing that is espec. made to counter wear and has a detent that keeps it from accidently unwinding if the sling is not in use. You can also store the Arms swivel inside the the bottom rear of the handguard if need be. You don't get all that for $2. bucks and you didn't count the loop you screwed into place from some other source, and no costs to meet gov't inspection approval. Lets be fair and not mix apples and oranges. The companies that build our defense systems have costs that allow them to answer the phone, have it in stock, heat/cool the building, pay the wages, pay their taxes, package the items, buy the fax and computers, do the engineering, and all the other little things that we all sometimes forget, but could you do that for two bucks? None of the gov't contractors are able to compete with do it your selfers and a hardware store with no spec's., rules, or special toleranced dimensions for our benefit in the field. If they were intending to get rich on 22 bucks, they would have made a spec. thread that we couldn't get in a hardware store. If the home made solution fails, will the hardware store replace it for you at no charge, fat chance. Food for thought. Good Shootin, Jack

Jack, my AR's are a HOBBY for me.  I am NOT going to use them for anything other than the range.  You're going a bit too deep for my situation.

Like I mentioned above, I've contributed to ARMS infrastructure already, and that's good enough for now.  I'm enjoying my hobby on E-8 pay, so that's the best I can do and I'm perfectly content with what I did with MY SIR and I'm going to use that $57 for something else, like feed my kids.

Good points though Jack, and thanks.  


Chris

Chris, I am referring to things in general and to all the position that I see all the contractors in. I have seen KAC and ARMS give freebie's out also to guys in uniform. I thought you were being a little harsh with "give me a break".
Good Shootin, Jack

Quoted: Chris, I am referring to things in general and to all the position that I see all the contractors in. I have seen KAC and ARMS give freebie's out also to guys in uniform. I thought you were being a little harsh with "give me a break". Good Shootin, Jack

I know where you're coming from Jack, but I'm the wrong person to get frustrated at.  

I think you probably had an idea from some of my previous posts that you had responded to that I don't attack anyone or any organization.

You need to know right now that there's isn't a company out there that I think more highly of than ARMS, their customer service, and the products that they make (which is a repeat of what I stated in the post you're referring to).

But Jack, I want to be frustrated that a short rail and swivel costs $57, not because I'm against ARMS and/or contractors, but because ....

It makes me feel alot better.


Chris

OK i guess since the KAC MRE is out of production i'll be getting the SIR. I would be getting the RAS 2 but don't like the little rail sitting up in the middle of everything and the step down for a laser that cost $5K for us peeon civi's.(i mean Pee on) My question is this...how solid are the side rails on the SIR ? If i mount a Surefire laser (mounted on a M95x surefire rail mount body) on the side am i going to have problems keeping zero? Is there any flex? Any flex would render the laser pretty much useless.Also how wide do you think it would be with a M952c on one side and the M95x laser on the other. My original idea was to use a MRE and mount the laser on the top rail in front of the front site and put the flashligh on the right side rail. I don't think it would be too wide that way .  Damn just when you think you have something figured out.....oh ya one more thing do these new #4 rails fit on the side?
Sorry so many questions but i have to be sure before dropping $400 on a handgaurd and who knows how much for 3 #4 rails.
Thanks guys.
GlenR

69, our MRE is in production, you don't have to accept second best (sorry Uncle Dick, I could not resist this).  We have them on the shelf.
P/N: 21166-1 has the plain front filler,
and P/N: 21166-2 has the Rail front filler.
Check out Quarterbore's site for some good pictures.
ColdBlue sends...

 M.R. R.A.S. II, S.I.R. by A.R.M.S. is second to no one.(sorry, I could'nt resist this either!! ha-ha)               soldier one
                                   

Quoted: .... My question is this...how solid are the side rails on the SIR ?  If i mount a Surefire laser (mounted on a M95x surefire rail mount body) on the side am i going to have problems keeping zero? Is there any flex? Any flex would render the laser pretty much useless.

The rails, when mounted on the side of the SIR, are even more solidly attached than on the bottom.  Along the bottom, the rails are attached by the screws only.  On the sides, the rail are attached by the screws and by studs on the rails that engage slots on the upper, metal portion of the SIR.  

So the rail mounting on the side of the SIR are plenty rigid for whatever devices you need to attach.

Also how wide do you think it would be with a M952c on one side and the M95x laser on the other. My original idea was to use a MRE and mount the laser on the top rail in front of the front site and put the flashligh on the right side rail. I don't think it would be too wide that way .

All I can tell you is it will be wide with a light on one side, and laser on the other, as you can imagine.

I tried my Surefire mounted on the side, but my thumb couldn't reach the pushbutton on the light, like I could when mounted on a KAC RAS.

Damn just when you think you have something figured out.....oh ya one more thing do these new #4 rails fit on the side? Sorry so many questions but i have to be sure before dropping $400 on a handgaurd and who knows how much for 3 #4 rails. Thanks guys. GlenR

If you'll look at 3rdtk's post above, he stated that the new #4 rail "....go only on the bottom of the SIR's".

So you'll only need one #4 rail.


Chris

Thanks Chris i am going to end up getting one of each SIR and MRE eventually but the SIR is coming first.I think it just looks bad as hell and the better cooling is a definite plus. Can't wait to see one setup with one of those Magpul MSS stocks. Should be very cool.
GlenR

Cold blue,
Does KAC have an official web site?It would be nice to have a place to get info about your products straight from the horse`s mouth so to speak. Thanks.

Unfortunately, KAC does not have a web site.
However, quarterbore has some of our MWS forends illustrated and explained about as well as anyone could show them on the internet.
Wes Grant at MSTN is another good source of information.  Both of these gentlemen have experience with the wide variety of products that are discussed here on ar-15.com.
If you have a problem or question that is best sent directly to KAC, I am more than happy to try my best to help.  My phone is (772) 562-5697 extension 239.
My e-mail at work is [email protected]
However, as the VP for Military & Federal Government Operations and Support, my primary mission at KAC is supporting them.  I also wear many other "hats" at KAC.  So what I am saying is that any response I would like to provide you may not always be instantaneous.
Also be advised that all my background is with mil-spec weapons and parts.  So, for example, I am not the guy to ask Bushmaster questions to.  Likewise, the only lights and lasers I haver used are from Insight Technologies--which are not only the best, but also the ones officially in the SOPMOD M4 Kit.  

Quoted: MRCR0603, IT'S GONNA LOOK LIKE THE HEADLIGHTS ON A HUMVEE, I.E., VERY WIDE. FOR THAT SET-UP, I'D RECOMMEND THE KNIGHT'S M.R.E. WHICH IS ALMOST AN INCH NARROWER. WES GRANT M.S.T.N. MSTN.BIZ

69Cougar - Wes is sending this reply your way, concerning your inquiry on mounting on the left and right of a SIR.


Chris