If I were in the market to buy or build another AR-15/M-4, which I'm not, I'd certainly look at the testing of individual components. The vast majority of today's offerings are certainly manfactured to government mil-spec standards. Are there manufactures who make weapons which exceed mil-spec tolerances? Absolutely, but they don't come cheap.
In my opinion, individual component testing is actually more important given that most components today meet mil-spec standards. The real question you should ask is, does the manufacture test each and every article or do they rely on batch testing where maybe only one component out of a hundred is tested?
Assembly houses typically procure components from various vendors and in many cases intermix components from different vendors on their assembly lines. I'd be suprised if any of these "assembly houses" conduct their own in-house batch testing of components they buy. I've seen assemble house uppers that only underwent functional test firirg of two rounds before shipping to dealers.
While the old saying, you get what you pay for is true! You should also look at the cost vice the benefit. There are many $3000 plus weapons sitting in safes which will never see an operational scratch or ding and may not get shot more than once a year. Guess there's nothing wrong with this if you can afford it but these weapons, in my opinion, are tools just like other hand tools we typically use every day. And, in most cases it takes several hundred or even thousand rounds to "wear in" the weapon, especially the BCG and trigger group.
Again in my opinion, most folks would be better off buying a fully tested weapon and lots of ammo. If you're really doing tactical drills the weapon is going to get dinged, scratched up, and dirty. But in the end you will know if you can count on it if a bad situation ever arises!
Regards
