View Full Version : AR15 upper receiver

May 6, 2011, 10:24 AM
I am in the market for a flat top upper receiver to replace my Colt upper receiver with the fixed carry handle.I have 2 Colts and 3 uppers between the two rifles,my Colt 16" carbine upper has a flat top and my other two Colt uppers in the 20" barrel are fixed handles.
Any suggestions on a well built flat top receiver is greatly appreciated

May 6, 2011, 10:47 AM
Are you saying you want a stripped upper receiver or a receiver group that's ready to fire? What barrel length, profile and twist rate? What do you plan to use it for? What ammo? Do you want it to serve a different purpose than your other 3 uppers? Too many questions now that you must answer first.

May 6, 2011, 11:07 AM
Thanks I should've been a bit more descriptive
I am looking for a good stripped flat top upper receiver and install one of my 5.56/223 20" Colt barrels along with existing bolt assy.,with thoughts of possibly replacing the factory barrel w/ a 24" heavy barrel varmint in the future to attach to the flat top receiver I am looking for now

May 6, 2011, 11:54 AM
Check out Rock River's EOP upper. Its like 1/2" taller than regular flat-tops so you shouldnt have to bend your neck as far down to see through your optics.

May 6, 2011, 05:02 PM
NWdude thanks I will check out RRA's flat top upper receiver

May 6, 2011, 06:17 PM
Since everything you currently have is Colt I wouldn't change that. Why have anything but the best and IMO Colt is the best. Check out http://www.specializedarmament.com/index.php?. They are a Colt supplier and sell Colt parts, including stripped flat top upper receivers, as well as entire rifles. You might also try http://www.gunbroker.com as they always have a wide variety of anything you could possible desire for firearms. You can probably find a good deal on a Colt stripped upper, or any other brand that strikes your fancy.

May 6, 2011, 08:05 PM
If you do move your 20" barrel over to a flat top stripped upper be sure you don't get an upper with M4 cutouts. The barrel extension on your 20" shoudn't have M4 feed ramps so you definitely don't want them in the stripped upper.

I also wonder if it's better not to break up an old Colt upper but of course the stripped receiver is the cheapest way to move up to a flat top.

May 7, 2011, 06:23 AM
Thanks I really appreciate the links and information.I didn't realize the colt parts were available,earlier I had gone to colts website looking for parts and didn't find any? Thanks again

Thanks for the information about the M4 cut outs w/M4 feed ramps fitting my 20" factory barrel.I need to do some research and educate myself on the difference between the M4 upper w/feed ramps compared to an earlier AR15 from the early 90's w/o M4 upper w/feed ramps?
I really appreciate your input and knowledge Thanks again

For now I am looking for the most economical way with quality to get my other AR into a flat top configuration w/o purchasing a complete upper or another rifle at this time.I figured after saving and purchasing a nice stainless heavy barrel,at that point I will put my colt fixed handle and factory 20" barrel back together.

May 7, 2011, 07:08 AM
If you thinking of a precision build take a look at the Rainier Arms billet upper.


I just finished a 6.5G build with one of these, very well machined part.

May 7, 2011, 07:22 AM
BCM has flattop uppers without M4 cuts for around $100. I've used a couple to do exactly the same thing. They work good.

May 7, 2011, 08:30 PM
madcratebuilder Thanks for the Rainer link looks like some precision ar parts w/ tolerances .0003 very impressive
Thanks again

karib Thanks for the BDM suggestion,I hear they have some very nice quality ar's and the price sure sounds good at a 100.00
Thanks again

May 7, 2011, 08:36 PM
Below are pictures of the four possible combinations of feed ramps. With your barrel you'd want the upper left and definitely want to avoid the lower left.

May 7, 2011, 08:43 PM
This may be outside of the box, how about modifying one of your existing carry-handle uppers and get exactly the flat top rail height you want?