For those unfamiliar with the evolution of AR rifles in general, DPMS started as Defense Procurement Management Systems and specialized in sourcing parts manufacturers for the M16 rifles, both new manufacture and replacement parts. Having that base of supply, DPMS started manufacturing complete rifles for the civilian market.
At various times many companies have taken up military arms contracts.
Signal Lamp Company made US M3 .45 submachineguns.
Rock-Ola (juke box manufacturer) made US M60 machineguns.
My issued M14 rifle in basic training was made by TRW, a satellite company of the 1960s era.
My first M16A1 rifle was made by General Motors Hydramatic Division.
GM-Inland Division made M1 Carbines.
National Postal Meter made M1 Carbines.
Union Switch & Signal Company made M1911A-1 pistols.
Singer Sewing Machines Company made M1911A-1 pistols.
Remington-Rand (typewriter company) made M1911A-1 pistols.
General Electric Company did all the R&D leading up to the Vulcan cannons and mini-guns, all based on a couple of old Gatling guns made by Colt Firearms back in the 1880s or so.
General Shaver Company (razor blades) made pistol magazines during WW2.
Union Fork & Hoe Company manufactured bayonets for many years.
Wilde Tool Company also made bayonets for the M1 and Springfield rifles.
On the other hand:
Remington Arms made a very fine line of knives.
Winchester made excellent padlocks, also some good pocket knives.
Oliver Winchester manufactured bicycles before purchasing the rights to the Henry lever-action rifles.
Hundreds of other examples exist.
The very first example of mass production was to standardize the parts necessary to complete rifles, rather than relying on individual shops making locks, trigger assemblies, barrels, and other parts. The old expression "lock, stock, and barrel" refers to the process of mass production of completed firearms by a single source with interchangeable parts rather than laborious hand-fitting of everything.
Standardized designs, interchangeable parts and assemblies within an established range of manufacturing tolerances, these concepts have been with us for about 175 years or so. Over the past 40 years or so we have seen advances in CNC machining, computer-controlled manufacturing devices, laser measuring devices that automatically adjust processes to compensate for tooling wear during use, these are the real news.
Completing a rifle (or other consumer product) with precision parts having minimal manufacturing tolerances to maximize performance, that is where the differences come into play.
Edited to add:
Colt did not invent the AR-15 rifle. The original manufacturer was Armalite Corporation with a design team headed by Gene Stoner. Much of the development work was done during the latter 1950's and early 1960's, and prototypes were submitted for US military consideration. At that time the US military was still heavily involved in trying to replace the M1 Garand rifle with the new M14, little more than a modification of the M1 to accept a detachable box magazine with a shortened (and less maintenance intensive gas piston/operating rod system) and chambered for the new 7.62mm NATO round (T-65, subsequently offered commercially as the .308 Winchester). Relatively few US military units had yet received the new M14 rifles, and President Kennedy was reportedly quite distressed while touring West Germany (circa 1961-62) to learn that our troops facing off with Soviet-aligned powers in defense of Europe were still using the M1 rifles.
The Armalite AR-15 rifle was rejected by the US Army. Colt Firearms purchased the manufacturing rights and successfully lobbied for adoption of the new rifle for military contracts (circa 1965-66).
A confluence of political considerations contributed to the adoption of the new M16 rifles. Years of delay in implementing the M14 rifle adoption, US involvement in Vietnam, and a new administration following the assassination of JFK all had effects on these decisions.
For those of us in the Army at the time the new M16 rifles came along, the plastic stocks and aluminum receivers, along with the "space age" appearance overall, led to a comparison with the popular television commercials of the day for Mattel toys; "YOU CAN TELL IT'S MATTEL, IT'S SWELL".
After months of training with bayonets and rifles used for horizontal and vertical butt-strokes in close combat, the new plastic toys were not quite as highly regarded as they seem to be today.
