Looking to purchase same but a few questions for those who've used one.  Need something to cool my barrel a little faster.  I tend to do a fair amount of rapid fire.  Would also like option of accessories.

1) Which should I order for my M4? Am looking to keep standard handguard cap, ie install without changing out any other parts.
RAS? Will RAS II work? what is difference?

2) With RAS how does panel on top handle heat?  Does it melt at all during rapid or FA fire?

3) Any other advice?

drj, rather than screw you up with half-facts, I suggest you go directly to Wes Grant at mstn.biz as that's where I head with all my RAS questions.

The RAS is good but does not allow for mounting of optics at the "ideal" location which is above the handguard ring.

The RAS II allows for this and is also a little bit better designed. However, the mounting surface it provides above the handguard ring is very short and does not allow for a wide range of mounting bases.
It is my opinion that KAC screwed themselves by doing this because a lot of people dont buy the RAS II for that very reason.

For example, if you want to mount an Aimpoint you are good to go. If you want to mount a Reflex, ACOG or other optic requiring a longer mount base, you cant fit it on the short mount provided. You have to mount it behind the RAS II wich negates the entire reason for having the RAS II in the first place.

I suggest the standard RAS or a slim line SIR from A.R.M.S.

I do plan on talking to him about this as well as other purchases. Sounds like good advice. Thanks much.

Marinesniper,
That's pretty much what I was thinking also as I will probably pick up and ACOG. Hard to figure it all out without actually getting your hands on the things and I have yet to actually see any of the stuff at a gunshow. They're kinda crappy up here. In fact I don't even go to many anymore.  Do better on the net. Thanks.

Did you read the thread tacked at the top of this forum?

drjarhead, the KAC RAS systems are excellent.  Also, you might want to look into an ARMS SIR system.  I have one on my preban Colt Sporter and I love it.

Yes. I'm pretty sure what I want but before I order a several hundred dollar piece I thought I'd ask a few questions. Thanks.

2) With RAS how does panel on top handle heat?  Does it melt at all during rapid or FA fire?

Most guys don't put a panel on top. It's hard to remove because of the front sight.  You'd need to remove the RAS to remove the panel.

I have the top panel on mine.  Heat has had no noticable effect on it at all.  I have a little more air flow into my RAS after I removed the bottom heat shield liner, which isnt a problem since I use a verticle foregrip (thanks KevinB).

Hey, I'm going to do that,did you drill out the rivets?

Grabbed on with a pair of needle nose pliars and twisted and tugged til the rivets popped on their own.

So you pulled the sheild out, but left the rivets still in? [8D]

-ed, done!

Nope, tugged hard enough and the rivets popped.

[:D]  Im not subtle

The RASII was designed to use either an ACOG (behind the hump) or a M68 (on the hump). Unfortunately, that leaves only the handguard for optics like the EOTech, which is what i'm using, and i don't know that i like it that far forward.

After shooting in rapid fire, don't forget to leave your hand on the vertical foregrip and not place it on the handgaurds.  [flame]

Nomex gloves rule