AR-15 - building lower, any uppers that won't mate well?

[jbauch357]

I'm building my first AR and doing it piece by piece for the lower but going to buy a complete upper.

Right now I have a .223/5.56 Stag Arms stripped lower, RRA lower parts kit and RRA stock.

Far as I know AR parts are pretty universal - but are there any complete uppers that won't fit well with that combination? I'm looking for an A3 upper of some sort, and have bene primarily looking at RRA, DPMS and S&W uppers so far...

 

[R.W.Dale]

Colt civilian uppers, difference in pin sizes

Vulcan Blackthorne Hesse, simply because the suck factor is so high

 

[jbauch357]

great, thanks for the heads up - haven't yet and will continue to not look at those as options...

 

[MT GUNNY]

The Colt thing, I'm Pretty shure it has to do with the TRigger Pin and Hammer PIn which is in the Lower. So you should not have a problem with a Colt Upper fitting.

 

[R.W.Dale]

The Colt thing, I'm Pretty shure it has to do with the TRigger Pin and Hammer PIn which is in the Lower. So you should not have a problem with a Colt Upper fitting.

NO this is incorrect, the difference is in the takedown pins that hold the upper to the lower, there may very well be a difference in pin sizes for trigger group parts also, I don't know. But that wouldn't apply to the OP

colt uppers use 5/16" takedown pins

mil spec and everyone else is 1/4" on the takedown pins

 

[crushbup]

Civvie HK 416 uppers won't fit.

 

[MT GUNNY]

The Problem KRockus, I actually Have a Colt CAR 3 "24 H-Bar Elite. It is Buy no means a "Military only" Firearm, Definatly Civilian AR 15. the Colt Upper (got it used in 2000) Fits Perfectly on my Less than a year old DPMS Lower. The Hammer pin and Trigger pin sizes Are Different sizes.

View attachment 91813

 

[R.W.Dale]

The Problem KRockus, I actually Have a Colt CAR 3 "24 H-Bar Elite. It is Buy no means a "Military only" Firearm, Definatly Civilian AR 15. the Colt Upper (got it used in 2000) Fits Perfectly on my Less than a year old DPMS Lower. The Hammer pin and Trigger pin sizes Are Different sizes.

View attachment 91813

I don't know the particulars about your colt configuration then. BUT depending on year Colt commercial uppers most assuredly did use a different pivot pin size.

http://www.biggerhammer.net/ar15/uppers/

 

[MT GUNNY]

Very Well, acording to that Link I have a late prodution A3 flattop.

I stand Informed and more knowlegable! Im suprised that link didnt say anything about the Hammer and Trigger pins, They are .015 larger than other brands.

 

[R.W.Dale]

Very Well, acording to that Link I have a late prodution A3 flattop.

I stand Informed and more knowlegable! Im suprised that link didnt say anything about the Hammer and Trigger pins, They are .015 larger than other brands.

as do I, because I didn't know about the hammer and trigger pin issue
http://www.biggerhammer.net/ar15/hammers/

 

[Hoppy590]

as said. aslong as you stay away from Vulcan/Hesse/Blackthorne/ Frank ( what ever they call themselves this week) you wont have any problems

 

[carbine85]

My M4 is a Stag upper on a RRA lower. The fit is tight and finish is a perfect match.