If you are not really into K-grip shooting, dose it make sence to spend the dough on a SIR system, or for that matter even a RAS ?

[b] If you don't need to mount anything (flashlight,laser,sling swivel, bi-pod, etc) and don't need the barrel cooling, you might not need an RAS[/b]

The Sir will still give you a full length optics rail (any pressure on a FF RAS (without the upper reciever mounting like the SIR) will cause loss of POI

I would have thought FF tubes would be good enough but when I grab my FF tubed 20in upper and give it[the FF tube] a pull it will move almost 1/10inch at the end [this translates to a lot of POI drifting if you aren't very Forend-pressure-conscious]

The SIR eliminates handguard heat buildup (as the SIR won't get hot very quick and the barrel will have much more air flow to cool faster.)

The SIR should always give you an increase in accuracy and consistancy of POI/Group size.

If you want to mount optics beyond the reciever the SIR (or a SWAN sleave is very important.)

[b] If you don't see enough reasons above to get a SIR- don't get one, they aren't completely neccassary but they are nice to have.[/b]

That helps. I do like to mount red dot sights in front of the receiver. I just started mounting a reflex sight on top of my M4 HG's with one of those rails that attaches to the top of the HG. It looks cool, it works perfect with backup sights, but to be honest with you, I don't think it's holding a zero for squat. Too bad ! Also, the HG slants down a little, and this may be a problem. I've heard many guys on this sight say not to mount an optic to a handguard, even a RAS, but I just had to try it. How dose the SIR feel holding it as a regular HG. My M4 HGs fit the palm of my hand like a glove, but it's just way faster to have that Aimpoint, or Reflex out front.

Is your AR a flat top?? You will have to have a flatop to install a SIR, but a RAS will work fine on any configuration.  I don't suggest mounting optic to handguards, unless it is free float.  If you do have an A2 upper, you can always look into a KAC free float RAS, or one of those Daniel defense copy.  I have heard the quadrail from C-More is nice, but it is kind of heavy.

I forgot to say reguarding light. While I belive that light should always be an option, I don't see it as warrenting that heavy Surefire M500A on my rifle day and night. I have the GG&G M3 rail mount attached to my M4 HG's at 10 oclock allowing me to take it on and off when needed. The same light mounts to my pistol, and fits in a Bladetec kydex pouch on my belt. I know that there is an adapter by GG&G that would allow me to mount this light to a SIR, or RAS, but then it would be at 9 oclock. Not as comfortable. I do have a flattop, and I know that a ARMS #38 ext. would solve this problem, but I just dont like the looks, or the flip up. Im selling one of these right now. Right now im using a Mark Brown.

Do you have to disconect the front sightpost to install the civilian SIR ?

No, you dont have to remove the front sight post to install either SIR models. On the C model, just remove the regular handguards and install the SIR C. On the M model, get a dremel and cut off the delta ring. Then the Weld Spring and Snap Ring will come right off. After that, install the SIR M.

C model will take about 10 minutes to install, the M model about 15.