AR Commercial Spec vs. Mil Spec

[sta500rdr]

I am looking at stock kits for my AR and I see some listing as Mil Spec, and some as Commercial spec. Some say that mil spec receiver extensions won't fit a commercial spec receiver and Stag Arms Stock kit says that it is supplied with a mil spec receiver extensions so that it is easy for aftermarket upgrades. Basically I just want to make sure what I order will work on what I have. It is a DPMS Receiver, I am assuming it is commercial spec. However, I don't know if this matters or not but it is stamped for "Safe" "Single Shot" and "3 Shot Burst".

Also, just a quick side question. If I order a left handed upper assembly will that work on any lower receiver? Do I have to have a left handed lower receiver or are they ambidextrous? Is Stag the only ones who make the left handed uppers?

 

[rob_s]

DPMS is most likely commercial.

Magpul has ways to tell the difference here.

 

[Glockman17366]

As far as manufacturing, there's not much difference. Testing or other QC may be more stringent.
It is, sometimes, more difficult to get a concession for a mil-spec product.

I work in QC at a company that sells to both commercial and government, so I know the drill.

BTW, the automotive and aerospace industries are more stringent then the government.