The drill jigs take care of the tolerance stack up.
Hopefully everyone who can, builds these. More importantly stock up on bullets and ammo before King Obama declares metal bullets illegal. Then, promptly go boating with said items.
I understand the concept of a drill jig. The rifle is still mostly purchased. Try making the barrel and chamber from scratch.
All you get with one of these builds is a lower receiver without a serial number. I fail to see how that is such an advantage.