I am looking for an entry level AR with a 20" barrel, .223/ 5.56x45mm. Now, with the 20" barrel, is a 1/7 twist rate better or a 1/9 with modern ammo like M193 or M855. Back to the main question, during my research, I have found that a lot of kits end up costing as much as an already assembled rifle. Is it more economical to build a rifle, and can one be built cheaper than $800? No bells or whistles, just a plain jane sweet 16. What are the advantages and disadvantages of building an AR? NOTE: I have zero gunsmithing experience, but have access to a gunsmith in the family that could help me with the build.