I’ve been looking at Colt AR’s a bit, contemplating getting one down the road someday, and was thinking that a Colt 6520 is pretty much what I want in an AR, well, except with an A3 upper. Does anyone sell one made in such a manner? A 14.5 inch with perm muzzle device wouldn’t hurt, but I’m sure that Colt sticks to 16" for civy and LEO rifles.
Hows about a 6920?
There is such a factory Colt M4 A3 LTWT 14.5", but I’m not sure what model it came from and it’s very expensive.
Look here at the first upper on the page:
http://www.fidelisfirearms.com/colt.htm
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I already have two M4’s. If I went and bought a Colt, I’d want a lightweight setup. 
Well a 6920 isnt techically a M4.
In this situation I would buy a Colt 6520 and swap out the upper receiver for a Daniel Defense A4 upper (has M4 ramps) and sell the Colt A2. If you wanted a Colt flat top upper receiver (to keep it all Colt) you could probably buy one from www.specializedarmament.com (but I’m sure it would cost 2-3 times as much as the DD).
I wonder if you could usethis upper from Brownells.
Brownells description says, “RECEIVER, UPPER, FLAT TOP, 16” CARBINE
FITS: AR-15 Match Target Competition HBAR II, .223; AR-15A3 Tactical Carbine, .223".
That means it’s a carbine flat top upper and should have cuts for the M4 feedramps which Colt carbine barrels have.
It should work for any current model Colt carbine build.
I’ve got a Colt AR6721 AR-15A3 tactical carbine.
Keep in mind that the linked receiver is probably “stripped” as in no forward assist or ejection port cover.
Plan on another $25 or so for those parts, much more if they are colt parts.
I realize it’s stripped. Couldn’t he use the forward assist and ejection port cover form the A2 upper?
Yes.
Colt upper receivers can also be found on EE at TOS. ADCO had them a year or so ago for $75 (used but not abused).
I have a non LEO Colt 6520 that I just can’t change up too much but I did pick up a 6520 upper and used a regular CMT upper to convert one with. I think it’s pretty handy for what I do.
I ditched the VG and rarely use the light, I have a tan SOPMOD stock arriving tommorrow that will pretty much finish this gun. It’s my favorite…for now.
Would he also need to change the front sight base?
John
No but he would need a taller front sight post (.040" taller). Bushmaster sells them for $5.50