hey guys, I'm thinking of doing a build with the following upper:

COLT UPPER - M16M4 A3 - COLT FACTORY UPPER WITH REMOVABLE CARRY HANDLE/FLAT TOP,- M4 MARKED NEAR DELTA RING ON CARRY HANDLE, COLT "C" MARKED ON RECEIVER, 14.5", 1/7 TWIST BBL, SIDE SLING, ADAPTER, NOTCHED FOR M203, NEWER STYLE FLASH HIDER, FORWARD ASSIST, LARGER STYLE HAND GUARDS, BAYONET LUG





I've never done a build with a colt upper before... and I'm kinda neverous about it because the large hole/ small hole thing gets kinda confusing for me.

First off, can anyone tell me if they know if this is a large hole or small hole upper???

I bought an RRA complete lower minus the buttstock for my build (I plan to use an LMT SOPMOD stock). The RRA lower has the standard mi-spec pin holes. I'm afraid if I buy this upper I won't be able to put it on my lower.

I have heard from others that brownells or someone else sells an adapter to convert large hole uppers to fit small hole lowers. How well do these adapters work??? Do they attach permenantly, making it so my rifle has to use the same lower/upper combo for the rifle's life??? How do these things work???

Lastly, do you think it is wise to mate a Colt upper to another brand lower. The reason I want to use my RRA lower with the Colt upper is because I hate that Colt FCG parts are nonmil spec. Using the RRA lower would solve this.

Any help you guys could provide would be appreciated. Thanks in advanced.

CK

sweet Lumpy.

Thanks... that makes it no problem at all.

Quoted: Thats a REAL M4 upper. Its small hole. Its also got a 14.5" barrel, which means you're going to have to add a perminent flash hider of a length that will bring it out to 16", unless you're going SBR.

Yeah... If I bought it I was planning on sending it to ADCO to attach a perm phantom. Thanks

Quoted: Lastly, do you think it is wise to mate a Colt upper to another brand lower. The reason I want to use my RRA lower with the Colt upper is because I hate that Colt FCG parts are nonmil spec. Using the RRA lower would solve this. Any help you guys could provide would be appreciated. Thanks in advanced. CK

It is a fine choice and will work well with your RRA lower.  Just be forewarned that RRA lowers are milled to be tighter where the rear lug mates with the lower.  This means it will probably be difficult to mate the upper and lower together the first few times.  Don't worry, this would be the case with any brand upper, even RRA.  


BTW, Colt also makes 16" M4 barrels, in both 1/7 twist and 1/9.  Just in case you wanted the choice.  

Does anyone have a pic of a LaRue 7.0 FF on one of these??? I want to use the LaRue 7.0 for my build as well; I would like to know how it would look in advance.

Thx

Quoted: Quoted: Lastly, do you think it is wise to mate a Colt upper to another brand lower. The reason I want to use my RRA lower with the Colt upper is because I hate that Colt FCG parts are nonmil spec. Using the RRA lower would solve this. Any help you guys could provide would be appreciated. Thanks in advanced. CK It is a fine choice and will work well with your RRA lower.  Just be forewarned that RRA lowers are milled to be tighter where the rear lug mates with the lower.  This means it will probably be difficult to mate the upper and lower together the first few times.  Don't worry, this would be the case with any brand upper, even RRA.

Thanks for the heads up.

Also bought a complete bushmaster lower minus stock....

which lower combo do you think would be better? This upper with my RRA lower or with my Bushy lower???

Opinions please.

The Bushy won't be machined tightly like the RRA. so you won't have to struggle with it.  I say try it on both and see which fit you like better, normal or insanely tight.  

Quoted: The Bushy won't be machined tightly like the RRA. so you won't have to struggle with it.  I say try it on both and see which fit you like better, normal or insanely tight.

Thanks again for the advise.

ETA: Gotta Love the night crew