At a high level of quality in the build a point of diminishing returns is reached. After all the components in addition to the barrel are addressed, trigger, optics, free float hand guard, load, the biggest factor is the Indian - not the arrow.
I would say that 80% of the above statement is true, but there are several aspects to a quality build that can make or break a true .5 MOA AR.
In the past 15 years the technology with Semi's has grown at such a rapid rate that a lot of people are overlooking the smaller details that when added up make a huge difference.
As I'm sure all of you have seen proper Gasport location has become a huge priority when making accurate quality barrels for semi autos, and now the gas tube design itself is being addressed. Several Firearms companies are noticing that a straight gas tube can improve harmonic's associated with The Recoil impulses and heat displacement that occurs at the current curvature of a standard gas tube. Just another tip to keep all moving parts parallel to the center line of the bore.
Putting your "quality" components together is properly is huge!!! We haven't even talked about cryo treatment, utilizing an oversized Barrel extension, bedding the barrel extension, truing the receiver face, gas tube alignment.... Hell, even your choice of Trigger and Hammer pins can cause erratic Flyers.
BUT!!!!
Back to the Indian and the arrow the problem with doing all these small improvements is that most people just do one or two of them and do not see the fruits of their labor on paper.
Basically there are NOT a lot of people that can shoot a semi-auto consistently accurate enough to actually see the increase in consistent repeatable accuracy.
Due to this fact most of these small but important improvements get pushed aside and labeled as Snake Oil, but couldn't be further from the truth.
