For those opposed to reddit links, here's his build list:
Build List:
* Aero M4E1 lower receiver
* Aero upper receiver
* Tacfire LPK (Do not recommend)
* Dead Foot Arms SCW 2.5 TAILHOOK PISTOL BRACE- FOR RIFLE CALIBER AR-15
* Sig Sauer grip
* Random ambi rear charging handle
* An extra rear sight I had sitting around
* A pmag, of course
* 7.5 inch 1:7 5.56 barrel from Grid Defense
* Gas block and tube from Grid Defense
* Amazon thread protector pressed in to a HKparts sight tower
* Top tub is a 7.2 (ish) inch 3/4th ID pipe cut to allow it to sit on top of the gas block and the gas tube passes through it in to the receiver
* HKparts forearm for mp5