I can't seem to make up my mind about what handguard to use. I would like to be able to use my detachable carry handle & cowitness an Aimpoint or Trijicon Tripower. I really would like just a drop in part, I don't want to remove the front sight or anything. Free floating would be nice, but not a must. Do any of you have experience with a set up like I am wanting?

Any kind of free floating handguard will require removing the barrel and/or front sight.  The RIS, RAS, and RAS II are perfect drop in models.  They just replace your existing handguard.  The RIS is an older version of the RAS and will fit heavy barrels.  The RAS will fit the M$ and lightweight (thinner) barrels.  The RAS is a bit more stable than the RIS, but that will only matter if you intend on putting some type of optic on it (ie some sort of Dot scope or a laser) For just a weapon's light and forward carry handle it should be fine, and will probably save you 20 or so bucks.  The RAS 2 has a "hump" that will connect directily to the existing flat top rail, and will allow you to mount an Aimpoint with the proper height for co witnessing with a back up sight and front sight.

I hope this helps.

Edited to add: You won't be able to use a detatchable carry handle mount with the RAS II (I just noticed that in your post.)

Only the SIR sytems does not require the barrel, front sight to be removed. The SIR M version requires the delta ring to be removed, but via a dremel tool and pair of needle nose pliers, about 5 min. time for the M version. The SIR C version doesn't require anything but the hand guards to be taken off.
Good shootin, Jack

RAS II doesn't need the front sight tower to be removed, it free floats the barrel and it's a drop-in installation.  It doesn't let you use the detachable carry handle though.

Jack, did you just "forget" about the RAS II, or did you leave it out on purpose? [;)]

Framer, don't destroy the value of your gun by hacking off the delta ring, go with the RAS II we make here at Knight's.
Much lighter, less expensive, doesn't flex like a "diving board", is more interoperable with accessory sight options as it does not raise the top rail but for a short distance in the middle.  Bottom line, it does the job right.
Cold Blue sends...

Lumpy196
Actually I forgot about the hump back whale.
Jack

Argue with Cold Blue?- no,SIR! [LOL][peep]

Whales are our friends, especially the kind that have rails [:)]

You mean Rhales.he he he....[:)]

Some good advice, thanks.
I think that I might go with the RAS, so I can use my carry handle still. I really like the carry handle with a co-witness optic in front of it. I may try the RAS II utilizing the hump for an Aimpoint or Tripower(I really want the Tripower, but do not know if I will see one in my lifetime)
Does the RAS work well, or is it not sturdy enough for an AImpoint? How much accuracy do you gain by free floating with the RAS II?
I do think that the RAS II is great, but cannot use the carry handle, that kind of bugs me. Do any of you have pics of your RAS II set ups?

[img]www.imagestation.com/picture/sraid35/pffcffcffff9f50f043093ca386d5e104/fd2ae503.jpg[/img]

If you have the budget for RAS series, you should really consider SIR. IMHO, SIR looks better, sturdier and cool your barrel faster.

I would like a scientific explanation of how EXACTLY the SIR cools the barrel "better and faster" than say an RAS 2 or FF RAS.  None has been able to do this and I dont see how its possible.  There are just holes in the unit.  No active cooling is taking place.

Anyone with a pic of an EOTech 551 + ARMS 40 + RAS II?

IMHO, If you are going to use Aimpoint I think SIR is better.

If you are going to use TA01/31 then RAS II is really perfect, except there is no rifle version available. (Me waiting for this)

You can only use M5 RAS, FF LONG RAS or Rifle SIR if you want to use TA11.

(Of course I'm forgetting all manufacturers except KAC and ARMS)

ColdBlue indicated the RAS II is lighter than the SIR.  Does anyone have the weight of the RAS II & SIR? (or at least the difference in weight?)

My SIR "C" is 19.35 oz.
RAS II is 14 oz. including three 11-rib (long) panels.  RAS II is only 11.25 oz. without any panels.
ColdBlue got a digital scale...
and remember 3rdPanzer, last time Captain Ahab harponned a "Moby Dick", he ended up "sleeping with the fishes" (as Tony Soprano would say).

Thanks for the info ColdBlue!

[b] DevL "I would like a scientific explanation of how EXACTLY the SIR cools the barrel "better and faster" than say an RAS 2 or FF RAS. None has been able to do this and I dont see how its possible. There are just holes in the unit. No active cooling is taking place.[/b]

I don't buy it either.  I think people are getting barrel cooling confused with the tendency of the plastic bottom of the SIR to not get as hot as the Alluminum rail of the RAS/RASII.  If you want to get technical I bet the RAS/RASII draw more heat off the barrel because they act like a heat sink.  But what the hell do I know?

Inkabee, you know a lot, you hit the nail on the head.
Heatsink.
ColdBlue sends...

Look .... you can shoot the SH*T out of a SIR equipped AR, and still be able to hold onto the polymer handguard portion.

That's good enough for me, and all of the SIR owners just on this board.

I'm wondering just WHO would YOU accept information from regarding the SIR and its design?

It's obvious the tests run by board members aren't enough .... so from WHOM do you expect to get this technical information from?  

You know, someone can contact ARMS through their website and have them explain how the SIR "works" in relation to barrel heat, but I'm sure that their response wouldn't be sufficient for your needs.

Another "RAIL" thread going in circles, pissin' on itself.


Chris

I just sent an e-mail to ARMS asking them about the rates-of-fire they achieved with the SIR, and how the SIR allows a weapon to achieve these rates-of-fire over a standard handguard, or even a RAS/RASII (if tested) equipped weapon.

Don't know what I'll get back, but I do know that they're prompt and courteous with their replies.

I'll post it as soon as I get it.


Chris

Ah oh, is this turning into another RAS/RASII vs. SIR? [:d]

I don't know if this is factual, but this is what I heard for SIR cooling capability -

A user can withstand ~16 mags full of automatic fire with STD SIR versions installed.

A user can withstand ~13 mags full of automatic fire with SL SIR versions installed.

I am not making this a pissing contest but I use a vertical grip so how long the handguard can be held has little influence on my purchasing decision.

To my knowledge there are NO STUDIES OR REPORTS on this site or anywhere else comparing barrel temperature of any handgurd system.

Many of you seem to not look at the studies and find faults.  For example the FIRSH vs SIR (FF RAS was not included BTW) measured the heat in the FOREARM not the barrel heat.  A FIRSH or FF RAS will have a hotter forearm 100% of the time as it acts as a heat sink.  If the heat is in the forearm then less heat is in the barrel right?  

Yet noone has determined which system allows the barrel to stay cooler and thus more accurate and have a longer life.  If you use a vertical grip who cares about how comfy the rifle is to hold?  In fact if you have to hold the magwell instead of the forearm who care about that either?  I would rather have a forearm that keeps the weapon from loosing accuracy or failing prematurely.  Id hold the magwell or lay the forearm on a support gladly if it would increase my accuracy and reliablity while keeping the rifle barrel from wearing out as fast.

I REALLY wanted buy a SIR but several things kept me from it.  If I had some kind of DATA to support it over my KAC foreend I would have purchased it.  So until the URX comes out I will use the FF RAS as a budget alternative.  If they come up with a SIR that mounts optics at the correct height and can come up with a reasonable explanation to why it will cool better than a FF RAS or URX I will buy it.  I am not dedicated to Reed Knight's products in any way.  I just like the best equipment and ask questions that challenge established dogma if they dont make sense.

Good points in your entire post.  

About holding the handguard .... it seems that with the rail systems, having the [i]ability[/i] to put out lots of rounds in a short time while effectively dissipating the heat is an important feature.



I get what you're saying, and it's a great point.  

Bottom line is that we're all pretty much AR enthusiasts, and not engineers, but there are board members that give it their best shot with their tests.

Which is MUCH MORE than I can say about my efforts.



Then if I don't have a vertical grip, then I won't be able to hold onto the foreend, right?

Isn't one of the points of the rail systems is to be able to dissipate heat better than the standard handguards, and probably keep the user safe from injury during high rates-of-fire?



Is it possible that if the SIR has a lower outer temperature, that the barrel also is cooler because the SIR is dissipating heat faster?



Again, great points that you mention.

For me, I'm pretty sure that there's a RASII that's going to compliment my two SIR's pretty soon!  [:D]


Chris

Just speculation but I would say of course the primary goal of the RIS then RAS and now RASII was to mount and modify equiptment to the issued weapon.  Cooling was certainly less of a concern.  Especially with the available foregrip.  Since the foregrip was involved larger "venting" holes could be used on the forend without concern of frying the operators hand as easily.  Seems the SIR is trying to remedy this with their plastic lower forend which it does a good job of.  But like anything it loses some attributes by doing so.

[img]http://www.imagestation.com/picture/sraid52/p898b80bdb2c969afd4f34f7508c7dd33/fc9a5b7e.jpg[/img]

This setup gives perfect cowitness with my ARMS BUIS. Its a RAS II bought from Wes. I love it. I like the fact I can put the lower panel on and use the handguard as normal comfortably as well if I think I'll need that or whatever.