I just received a 20" 1/12 pencil barrel from Green Mountain for my project. With shipping it came to $181.57. I ordered it on March 24 and received it on March 26.
It looks good. Just wanted to add that the feed ramp has a M4 cut if that matters to you. I'll know how it shoots in a couple of months when I've gathered and assembled all the pieces parts.
Barrel:
http://www.gmriflebarrel.com/m16-a1-...ist-20-barrel/
I ordered a front sight base (FSB) from Double Star. Non F (no mark), parkerized, .625.
FSB:
https://star15.com/dsc_front_sight_tower_no_mark.html#
I hope I ordered the right FSB. It's for use with a cheap A2 upper I found. Not an A1, but close enough for what I'm doing.