Well I'm not the patient type, my new M4 upper is probably still weeks away, so I thought I'd slap the M4 RAS on my current M4 upper.  I have the handguard tool, I can swap standard handguards, M4 handguards and Fobus handguards all day long.  For the life of me I can not get the freakin RAS to fit.  Wondering if my gas tube is a hair larger than that hanging rear retainer thingamabob.

I have it hanging dowm the way it should, front of the upper handguard inserted into the retainer, delta ring depressed and the damn gas tube pushes the hanging retainer back up which won't allow it to clip under that circular ridge piece under the delta ring.

Struggled for half an hour, no go... I'm just hoping its something simple.

Is the hex screw out?  If the retaining clip is in hanging free (w/o) the screw) it is much easier...


Kevin

Yup, screw was completely removed... like I said, it hung all the way down but the gas tube seems too big to fit between the prongs on the hook...  Seller of the new upper has volunteered to take a crack installing it for me.  Still, pissed it doesn't fit current upper.

Hmmmmmm, I don't have my roommate's calipers handy...  The front is not the problem, that fits cleanly it.  I cant get the rear of the handguards down by the delta ring.

If you have a stiff delta ring weld spring you may not be able to install this without the help of a second person.

When the rifle is propped vertically the retainer will not hang down as it should it has to be installed with the rifle kind of parallel to the ground and sights up.

Mine took a couple trys to install.  It's a tight fit.

Hiram- I had a similar problem installing my RAS to an M4 and came to find out that the barrel was canted, For some reason it was a "C"-hair off.  

Try using some 550 cord around the retainer to pull down on it when it makes contact with the gas tube.  Your gas tube is MIL-SPEC right?  Then seat the rail and using the 550 cord to mantain correct position of the hanging retainer, gently squeeze together.  It sucks to do as one person unless you have a vice to clamp the receiver in, you might want to involve a third person to deal with this assembly (Monkey-FuXXing-A-Football) but it does go together with out force, but requires finesse... Remove the 550 cord before it gets caught in the retainer too.  That is an individual judgement call as to "WHEN" to remove the 550 cord.  Took me about 5 tries to get the whole thing together.

 WARNING - Your RAS will be a hair off also!  If you install a Arms#38 EX-MOD or EX-MOD-L it will fit VERY FRIGGIN tight!  As it is realigning/flexing to the cant of the barrel assembly.  If you don't mount an Arms #38 EX-MOD (L) and mount a sight directly on the RAS be prepared to do a bit of "clicking" to bring the POA to the POI.

 Course, this is just my predicament I found myself in.  Individual results may vary...

Edited to correct spelling errors....Mmmmm Vodka....