I went with a regular 16" M4 profile barrel, but that's what I wanted.
I actually got this one:
http://www.jsesurplus.com/custom16hbarmidlength1x9flattopuppercompletestandard-2-1.aspx
I put on a Magpul MOE Handguard, YHM Phantom Comp (Had to blind pin it because of NJ Laws), Badger Gen 2 Tac Latch, RRA Bolt Carrier, Low Profile 4 rail Gas Block.
Worked flawlessly at the range too. I plan on using it for 3 Gun when I get the time.
The rest: Spikes Stripped lower, Palmetto state armory MOE lower build kit (PSA Lower Parts Kit, MOE Grip, Trigger guard, and Stock - Pinned cuz of NJ Laws, Mil spec buffer tube), added on a Magpul ASAP and BAD. Optic is a Vortex SPARC.