M4A1 SOCOM Block 2 FSP Upper Receiver, Military Special

Assembled to Order, Ships in 5-8 days, pin and weld services will require additional time
M4A1 Block 2 FSP with Colt receiver and Daniel Defense rail and Surefire 4-prong

M4A1 Block 2 FSP Upper Receiver, Military Special

This is top shelf.  You might not need top shelf, but if you want it, this is it.  Charlies's Custom M4A1 with the FSP / front sight base and all the bells and whistles.  Period correct.  Dope ! 

We held nothing back with this upper receiver group.  Colt "C" marked upper receiver, Colt SOCOM 14.5" barrel with Surefire 4-prong flash hider, Daniel Defense M4A1 FSP rail in FDE, Colt BCG, and Tango Down Scar Panels and Vertical Forward Grip in FDE.  The Block 2 is a great rifle, and some like the flattop rail, but there is just something that says classic about the Front Sight Base rig.

Ready to pick your optic and rear back-up sight of your choice.  Charlie's likes the Matech 600 meter for iron sights, and your choice of a tan EOTech or Aimpoint M68 sight with a Wilcox mount, or maybe an Elcan with RMR.  You can even put a Trijicon ACOG on if you wish.  Just be sure to match this up with a Colt lower, laser-cut ID sticker and B5 SOPMOD Coyote stock and a sling for your rig.


Built to Charlie's specifications by Potomac Armory


  • Colt Upper Receiver with "C" stamping from circa 2013.  We have keyhole (Cerro Forge) and square (Brass Aluminum).  You can make a request for one or the other, but no guarantees.  We do not stock them differently.  We will have options for a CAGE Code upper, if you are interested, which can save you a little.
  • Daniel Defense M4A1 FDE rail for FSP
  • Colt 14.5" SOCOM profile barrel, standard chrome-lined 1:7 5.56 NATO
  • Properly timed Surefire 4-prong SOCOM flash hider (FH556RC 1/2-28), with an option to have pinned and welded for $85.  Contact us at check-out if you want this option.  Note that as-is, a 14.5" could be creating an NFA firearm, and you must fully understand and comply with the law.  We also have other flash hider options, if a 4-prong is not what you need or want, less expensive options are available.  Ask us.
  • Colt factory Bolt Carrier Group
  • Colt charging handle
  • Tango Down FDE full vertical grip and Tango Down FDE Scar rail panels (2:  one for right side and one for left side)

Pictures courtesy Potomac Armory, clonerifles.com and the US Department of Defense