The difference in quality between manufacturers is less now than it has ever been. The manufacturers don't actually make there own parts, they just contract out to have them made and there names are added to the CNC program.
Depends on the brand. S&W had QC/QA issues with externally sourced lowers & bbls, so they brought those items in house. They also began sourcing HPT / MPI bolts for their carrier groups. LMT & Colt also make many of their own parts. There are strong indications that BCM parts are supplied from a particular company which makes rifles for the military. Spikes sources similarly spec'd parts. Daniel Defense makes their own lowers, makes their own lower parts, cold hammer forges their own bbls, makes their own sights, and makes many of their own accessories. DD is the sole source supplier of the RIS II to US SOCOM. LMT makes many parts, like their SOPMOD stock, for US SOCOM.
The century barrels and recievers are identical to those used in any number of other manufacturers. The used parts came from military rifles that actually exceed quality of the guns made for the civilian market.
Century doesn't even tell you what steel their bbls. are made from, and they aren't hard chrome lined. Colt, LMT, and DD make their own hard chromed barrels from 4150 steel - these are mil-spec bbls. BCM & Spikes source equivalent bbls. S&W, and many others use slightly lower grade 4140 steel on their chrome lined bbls, but as mentioned above S&W does it house. Noveske actually uses M249 SAW bbl blanks to make their M4 / AR-15 style bbls - exceeding military spec for such bbls. Civilian guns are readily available from these makers. In fact, aside from the full auto bits, and the 16" bbls; a rifle from Colt (Blue Label Models), LMT, DD, Noveske, Spikes, or BCM will meet or exceed all military specs.
There is a tendency for people to look down on a product because it costs less. Wit AR 15s, you are often looking at the exact same product with a different brand name on it, kind of like name brand fruit loops and store brand "fruit rings".
Actually, if you'll read back through the thread no one is taking issue with Century because of price. The issue is that you can get an all new rifle with better parts for the same price as a Century.
I'd rather have an off brand rifle and 500 rounds of ammo than a name brand rifle (made with the same parts) and not have any ammo.
I'd rather have a rifle built with better quality all new parts for the same price as a rifle built with a mix of used parts & lower quality new parts.