Fella, I don't know who you are or what you've done, so all I can go by is what you're posting here, and you'll have to count me in the group that thinks your full of chicken something. I'm not seeing any useful contribution here from you, I'm just seeing an arrogant guy with a chip on his shoulder against gunsmiths.There are tons of references in those legacy things people don't use any more called "Books."
There are a few other web sites you can sift through (try Brian Enos for three-gun, and nationalmatch for highpower rifle).
John Feamster (author of Black Magic and one the USAMU loaders in the Custom Ammo Shop) holds a few National Bench Rest Shooter Association (NBRSA) and International Benchrest Shooter (IBS) "Official Screamer" groups (five shots in .099 at 100, or ten shots in .199 inches; five in .250 at 200, or ten in .449 fired in verified, scored competition) using ARs 'smithed by Bill Wylde. Zediker, Tubb, Sweeny, and McKee all have good books your library can get you for free.
There are lots of things you can do -- like bedding uppers to lowers; truing upper receiver faces and bolt faces; using forcing bolts from the bottom; using split pins; heating uppers and force-fitting extensions into the upper, etc. Expensive to do (billable gunsmith-time wise) that may or may not give significant improvement for a team of four to sixteen guys to maintain across five uppers each.
My advice is good for exactly what you paid for it. Whether or not you use it is absolutely and completely up to you. More than a few on this site say I'm full of chicken feathers.
Your assumption that anyone who disagrees with you must not read books makes you sound like an arrogant fool. I read 2-3 books a week on average, but that has little or nothing to do with the topic. There is plenty of information in books that completely counters your assertions as well. There's also plenty of good info online, like the Accurate Shooter link above. If you prefer to disregard guys like that who're actually building accurate rifles, that's your issue, personally I'll choose to try their tricks and see what works for me.
Claiming that things like shimming/bonding or thermofitting a barrel to an upper doesn't improve accuracy is silly; it's easily provable that it can, to anyone willing to try it. Obviously that doesn't help on every rifle; if you start with one that's already tight, it won't give the same improvement as comparing to a common "mil spec" upper and barrel extension. That's just one example of many tricks that CAN improve a rifle that needs it.