I found myself in possession of most of the parts to slap together another AR upper, and happened across a set of 20 Tactical dies by Hornady so I thought I'd try one. I'll be machining the barrel from a Black Hole Weaponry blank, so I thought I'd post some pictures of the process here for anyone who might be interested. (And I figure it's fair to call this a "build", since I'm actually making the barrel myself.)

Here's the parts I'm starting with, still need a handguard. AAC receiver, some sort of nitride BCG, generic adjustable gas block, and a Fail Zero barrel extension. The truck axle is a 24" .20 cal 1:10 blank; basically a solid bar with a rifled bore. Pardon the low light cell phone pic.
[Linked Image from i.imgur.com]

This'll be a work in progress; I've just started and will be working on it as time allows so I'll update the thread as I go. I'll add a few more pics below though.