I've wanted an AR15 for a while.  This is my first build, and all that I've learned has been from this message board.  (Thanks to everyone!)

So far I have received my 14.5" CMMG barrel with a Phantom flashhider . . . and misc barrel parts from Rock River Arms.  The photo below shows the 14.5" barrel with the RRA CAR handguards (I can't afford to float it right now), sling swivel, and hidden front sight post components.

http://www.mlogiudice.com/outdoors-guns/photos/145barrel_w_guards_deltaring_swivel._small.jpg
(High Resolution Image Here)

I've got an A3 RRA upper & RRA lower on order w/ match trigger, hogue grip, collaspable stock.  I've got qty=3 30 round magazines already loaded and waiting.  . . . problem is that I'm waiting on the delivery from RRA.  At least, I placed my order on September 16.  RRA is currently quoting 6-8 week deliveries on lower receivers, per their sales associate.

This being my first build/assembly, I have one question:  Will my RRA upper work with my CMMG barrel?  The CMMG barrels are supposed to have "M4" feedramps.  I have no problem with filing\polishing my RRA upper to match the feedramps.

http://www.mlogiudice.com/outdoors-guns/photos/m4feedramp_small.jpg
(High Resolution Image Here)

Inspection of my CMMG barrel doesn't show pronounced feedramps, as shown in the recent feedramp thread (here.)

There are plenty of other companies making great upper receivers, I would not be waiting that long to get one.....

That looks like an M4 extension.  Are there little cutouts at the end of the extension when viewed from the bottom, like pictured below?

Rock River quoted me 5-8 weeks on August 10 for 3 lowers.  Going on nine weeks and still waiting.

Heck. Why not grab an upper and a lower from Warren at Ameetec Arms? I know he has them on the shelf. I've put some of his stuff together and it all clicks together like leggos. No worries.

Luck,

SD