FBI "HRT type" custom 11.5" Upper Receiver Group

$1,499.00 - $2,834.00
built to order, allow 3 weeks to ship

FBI "HRT type" custom 11.5" Upper Receiver Group

An exclusive for Charlie's is the FBI HRT URG - limited edition

Custom upper build from Potomac Armory, made originally for federal law enforcement agencies.  This is an HRT style short barreled upper receiver is now available for civilians, as a limited edition.  

Made with traditional FBI spec'd parts, the FBI upper is similar to that used by HRT and regional FBI SWAT teams.  Starting with a premium law-enforcement spec premium forged 7075 M4 upper receiver and premium mil-spec bolt carrier group, the FBI upper receiver group sports a Geissele 10" Mk4 Federal rail in OD Green, with pronounced Picatinny rails at the forward end for tactical attachments. Troy folding M4 back-up iron sights are standard, and the operator can choose a Colt FBI 11.5" heavy profile barrel, or a Colt 11.5" government profile barrel, both with Troy low profile gas block, and a choice of tactical flash hiders from Surefire, BE Meyers and Knights Armament, to support a variety of suppressors.

The Colt FBI barrel is coveted by many collectors, and has Colt markings under the rail.  The Colt 11.5" Government profile barrel comes to us with a pinned FSB. We remove the FSB and, prior to installing a Mk12 block, the front pin groove where the front sight was pinned will be chemically blackened. This will be visible if you look real hard.

The FBI URG from Potomac Armory is quite capable, and very versatile.  The 11.5" Colt FBI barrel performs very well with fully automatic fire, while the Colt Government profile barrel is quite capable of suppressed or unsuppressed fire.

The Aimpoint T-2 optic is optional, and mounting options offered are a Daniel Defense riser mount (SWAT model) or the Spuhr HRT version.


  • Mil Spec premium forged M4 upper receiver, black anodized 7075 aluminum
  • Geissele ACH profile black charging handle
  • nitrided MP tested bolt carrier group, full auto M16 profile
  • Choice of either a Colt 11.5" FBI heavy profile barrel of a Colt 11.5" Government profile barrel, both 4150 steel alloy barrels, chrome lined and black phosphate coated in milspec hard coating and finished with oil.  Both barrels are factory Colt barrels with 1:7 twist and 5.56 NATO chambering, and high pressure tested and magnetic partical inspected.  These are top quality barrels.  The FBI profile barrels will be virgin 2015 production barrels in 2021 while supply lasts, and then switch to 2020-2022 production barrels which originally had a front sight post, and then removed and chemically coated for corrosion protection.
  • Troy low profile gas block on the FBI Barrel, and optional on the Government profile barrel.  Government profile barrel comes standard with a factory mounted two-pin low profile gas block (the shaved-down A-frame FSB model).  If you would like the Troy gas block, that is offered as an option - put in the comments, and we will move to that barrel, if a virgin barrel is available.
  • Geissele Mk4 Federal 10" OD Green rail
  • Choice of military grade muzzle devices: BE Meyers 4-prong premium engineered flash hider; Surefire 3-Prong SOCOM, Surefire 4-Prong SOCOM or; Knights Armament NT4 QD
  • Troy folding M4 back-up iron sights
  • Optional Aimpoint T2 red-dot optic with Daniel Defense riser mount or Spuhr HRT mount
  • multiple sling quick disconnects allow for easy attachment of a sling of your choice.

NFA Notice:  This upper receiver group, when mounted on a rifle lower receiver becomes a Short Barreled Rifle (SBR), which is tightly controlled and registered by the ATF.  You may mount this upper into a lawful AR pistol lower, and not have an SBR.  Be sure to understand the NFA laws and your local and state laws to make sure you can lawfully own this.  Also note that mere possession of a short barreled upper and an AR rifle lower in close proximity may be a violation of the NFA.