is it true that there are only a couple or several companies worldwide that manufacture ar15/m16 MILSPEC parts?

like lowers etc.,?

Yes, all of the manufacture's buy the forgings (or castings) and internal parts from contractors and then they do their own detail machine and finish work. Here's a couple;

[url=yankeehillmachine.com/products.html]Yankee Hill[/url]

[url=continentalmachinetool.com/firearms.html]Continental Machine Tool[/url]

That's sorta right.  Nobody makes everything for their rifles.  Lots of small parts come from a pool of small companies and special stuff like plastic and forgings come from others.

Most of the "factories" you buy from aren't factories.  They're a few guys in garages or strip malls (Check out ASA) with a couple of guys putting rifles together and some ads.  They have to have a "manufacturers" license anyway so call themselves manufacturers.  They're really assemblers.  The problem with these companies is that they don't have any quality inspectors to speak of and the quality of their rifles ranges from great to bad depending on what parts they got in this week.

Sometimes they use pictures of stuff being machined that come from their suppliers.  You can't tell.  Even Colt, FN, Bushmaster, and ArmaLite buy from outside suppliers.  I don't know if Bushmaster really makes anything big (I think they get their receivers from Continental or LAR) but Colt FN and Armalite do.

Check out the websites and see who does what.  It would be interesting to pin them down to see what they really do make.  We should have them publish pictures of their "factories"

To further elaborate, some manufacturers, while they don't make their raw forgings in-house, have the big forge houses making receivers for them with their own dies.  Armalite comes to mind - they don't buy the same raw forgings ASA does, but have them made specially for them with their own dies.

The "manufacturing" comes about when they machine a functioning receiver from those raw forgings, the tolerances they maintain, the metal finishes used, and the QC applied to the steps of the process under their control.

A manufacturer who doesn't machine their own receivers from raw forgings or castings is basically just an "assembler", though.

I believe Olympic Arms is the current AR manufacturer who does the MOST actual manufacturing of their own parts from raw materials in their own facility.  They're one of the few AR makers who manufacture their own barrels and bolt carriers.  They machine their receivers from raw forgings and their own castings for both upper and lower receivers, and have the capability to machine them entirely from billet if they wanted to, although I don't think they do so for cost and productivity reasons.

Socom Manufacturing in South Carolina makes their own "Diamond Series" line of lower receivers entirely in-house, machined from billet.

Most, if not all of the big three ABC which is Armalite, Bushmaster and Colt. Draw from a large pool of subcontracted work. It makes dollars and sense.  

this is the exact reason that i buy Century forged recievers. made by CM just like Colt, RRA and more. if i covered the left side fo the mag wells with tape and challeneged you to pick the century from the colt, rra, and bushie you couldnt. at $89 they are a steal!!!!

Century's Web address please.  Thanks

Got mine (first build) about 2 months ago from ^^^^ Mr. Murray.  Was perfectly happy with it.  No big problems during assembly.  Fit/Finish were fine.

Rob