I am looking to buy a RAS M5 for a new BCM 20" upper and I am slightly confused on the differences. I went to quarterbore's web site to look at the differences and I think I am over thinking things. Is there only on rifle length RAS? The M5? I know there is the RIS and RAS II, but I want to be sure that I buy the rifle length M5.
Also, are there certain things to look for to be sure it is not a fake? I keep hearing about copies of these things and want to be sure I don't end up buying an airsoft product or something.

Thanks!

The M5 RAS is the one you want I didn't see anything on the EE but there was this one on Gunbroker but the price is kinda high for 05 production. Keep checking the EE and you will find one at a good price. Hope this helps.

Also, does bbl profile matter on the M5?

I have heard some heavy barrel profiles wont fit. But, I put one on my Colt HBAR for a short while and it fit fine.

Also, some of the fakes I have seen have a screwdriver slot instead of an allen head on the fastener at the rear of the top handguard.

Thanks for the replies. But - are all rifle length RAS' M5's? Is there another kind of RAS that is rifle length and not an M5?
Thanks

The M5 RAS is the mil issue.  Drops in and non-free float.

There is also a KAC free float rail that is rifle length, and the free float URX rails.



The standard AR heavy barrel will work with the M5.  Extra heavy barrels will not.

I believe that some real KAC rails have a standard screwdriver slot.

There are other KAC RASs that are rifle length, the URX, the FF RAS, and the SR25 RAS.  Those are all free floating systems, as opposed to the M5 RAS which is a 2 piece non-free floating system.

ETA:  Have a look:  http://www.knightarmco.com/mod_weapons_1.htm

I found one just like the one on GB for 85.00 new but it had no rail covers.

I have seen some on the EE in the past for about 150.00

You just have to keep an eye out.

With the BCM's being realesed after so long eveyone who got one is looking for the rails.

I just got lucky.

the rifle length m5 will fit barrel diameters,at the fsb, of .825-.875" or so, without modification. hbar's are .750", so gtg. bulls are 1.0"so no go,w/o mods.(it's easy to make the radius larger)
fyi most .308's are 1.0" at the fsb.i've picked up sets for 50.00$ with extra covers, and 70$ with no covers. picked up a cover kit with a variety of covers and a vfg for 40$