This is great combo. I put a PC lower on a Spikes Lightweight upper with a pencil barrel and topped it with a moderately priced Vortex red dot and a Magpul BUIS. Simply flawless. It's an easy 2 MOA until it get hot. It was sighted in with M855 seconds without a single malfunction. I'm also impressed with the Vortex Red Dot. I'm a bit concerned about the BUIS. It's strictly an emergency sight only. The whole rig comes in a bit over 5 pounds.