TexasCHLforum.com

I'm no AR expert and certainly not a gunsmith, but I have built from a stripped lower using the exact parts I wanted and attached it to a pre-built upper. It's not that difficult at all and there are very easy-to-follow directions at web sites like AR15.com

Seems the upper build - specifically attaching barrel to upper receiver - is the "most difficult" part of a complete build (thus why I avoided it).

Also, make sure you want the fixed front sight if you think you might install a "basic scope" - YMMV but I had difficulty with standard rifle scopes (e.g. a 3-9x40 Bushnell) with the front sight post - while you can see "through" or "around" this giant hunk of metal (fixed sight) in your field of vision I still think your best bet if you plan to run such an optic is a folding front sight.

Lastly, make sure you know WHY you want a 1/7 twist barrel. I believe 1/7 is the standard for US military now so they can accurately fire/stabilize heavier grain bullets (up to 77 grains). But 1/7 twist will not work well with anything lighter than 55 grains, and in my experience shooting 1/7, 1/8, and 1/9 twist barrels the 1/7 twist even leaves a bit to be desired in terms of absolute accuracy with 55-grain bullets (which are the most prevalent available ammo for consumers - supplied at every Wal Mart, Academy, etc). 1/7 will certainly shoot 55-grain bullets with good minute of COM or minute of bad guy accuracy, but don't necessarily expect 1-inch groups at 100 yards. 1/9 shoots 55-grain very well, but can have some stabilization issues with bullet weights in the 69-77 range. 1/8 is a good compromise. My 1/8 barrel (a 16-inch Sabre Defense stainless fluted stainless) can shoot bulk American Eagle 55-grain 1 MOA or less and also make groups approximately 1 MOA with 69 and even 77 depending on bullet design etc.

Point is, be sure you get the twist rate that will best fit the ammo you think you'll have/stock or be able to acquire when you need it. Any of the three will likely be fine, just depends on your tolerance for accuracy. But 1/7 seems to be an "upcharge" item with some makers.