Hey everyone!

Just a quick and probably dumb question....When I'm building/putting together my AR does it matter if the manufacturers are different? i.e. Upper from RRA and Lower from Bushmaster and barrel made by Colt, Bolt assembly from Stag, etc....You get my drift....I'm trying to estimate if I can build one to spec with what i want or purchase my friends for about 675 with an A2 upper, AK compensated 16" barrel.

Thanks for the info fellas! (and ladies if there are any out there)

Infinite1

Typically not, but sometimes they don't fit.  I would recommend keeping the major components as complete systems.

I myself have a bushmaster upper with an Olympic lower and got an eo-tech with the money I saved.  I've had no problems with my set up.

I am not one to worry too much about aesthetics but if you do, keep in mind that the finish on parts (lowers and upper being the most obvious) can be different shades of dark grey.  Some even look a bit purplish I hear.  Thus, it is possible that your parts will look mismatched.  Probably won't keep the weapon from working though.

I have an Olympic upper that fits nicely into my DPMS lowers.  The upper and lower receivers are made (supposedly) to within the same specifications.  Most are just finished from forge blanks that are made by various forges around the country (Alcoa, Cerro, Anchor-Harvey, Cardinal, etc.).  I don't know of any uppers and lowers that won't mate up correctly except this one:  www.ar15.com/forums/topic.html?b=3&f=118&t=293546

He has a Stag lower that's out of spec, and he's having to get it exchanged (for free, of course, since Stag blew it, not him).

ETA: As far as different finishes, my Olympic upper exactly matches my DPMS lower, and my DPMS upper (bought separately) exactly matches my other DPMS lower.  I've only seen some Colts and Bushmasters that were gray (Colt) and purple (Bushmaster).  The rest are pretty close in blackness.

Never had a problem using various manufactures parts.

My last build consisted of

Stag lower, RRA LPK
CMT upper, Bushmater 16" HBAR
CMT B,BC,CH

everything was purchase from vendors on the EE or from individuals on the EE except the Stag lower that I got at a local show.