The TDP or technical data package is based on 50 years of building a fighting gun. It’s the bare minimum of what the govt requires and what most consider a good starting point.
Things like 7075 aluminum receivers with a hard coat anodizing on it. 4150 barrel steel and chrome lining. Specific sized gas ports for specific ammo. Carpenter 158 steel with a good heat treat, shot peened, HPT tested and then MPI’d bolts. Specific steel on the gas key and specific bolts to hold it on the carrier. Specific 7075 aluminum RE’s threaded a certain way and castle nuts staked into an end plate that is not too hard nor too soft.
These are just a sampling of what is the makings of a decent AR. But companies cut corners and use 6061 rather than 7075, 4140 vs 4150 barrel steel and nitride vs chrome lining. Gas ports opened up to run cheap lower pressured ammo. Cheap extractors and spring kits, different steels for the bolts and nitride over chrome on the inside of the carrier. Softer screws holding the non chrome lined key. Commercial RE’s loctited instead of staked.
I could go on but surely you get the point. Yes there are better barrels and better triggers, Better furniture and better receivers. But the TDP is the place to start if you want a quality gun. If you want to take chances go ahead but understand why the cheap stuff is cheap.
I agree as far as war fighting rifles go. The blueprint/specs to making a functional AR even if out of lower quality materials is well established at this point being one of the most mass produced and tested firearms in world history. For a range or even home defense gun that is kept cleaned and oiled, that is not going through mag dumps or being carried all day in extreme desert or jungle environments, and beat to hell by 18 year olds in a war zone most any will be reliable in my experience. It won’t be as nice or as good but I’d expect it to go bang when pulling the trigger.
The difference between military grade and better Vs a cheapie is stacking the deck in your favor when the rifle has been subjected to heavy use and extreme conditions. Not a semi auto kept cleaned and going from safe to range or to engage a bad guy climbing through a window.
