FBI HRT Geissele Mk4 Federal Rail and Barrel Kit - 11.5" Daniel Defense

Discontinued by Manufacturer, not taking orders at this time

FBI HRT Federal Rail and Barrel Kit - 11.5" Geissele - Daniel Defense

Starter build kit with Geissele Mk4 Federal FBI rail

If you are looking for the basics for an FBI HRT build, this is a great start.  Charlie's has partnered with Potomac Armory to bring you a balance of the right parts and not break the bank.  This is the current production Geissele 10" OD Green Federal (FBI) rail with laser etched T-marks.  We have selected a Daniel Defense Cold Hammer Forged 11.5" barrel with a Troy gas block and stainless steel Remcon Defense gas tube.  A Surefire 4-Prong 'fast attach' flash hider rounds out this offering.

The rail and barrel kit will fit a mil-spec upper receiver.  Potomac recommends forged receivers, like Colt, LMT, Daniel Defense, Bravo Company, FN or Rock River to name a few.  Billet receivers sometimes do not do as well timing to the Geissele rail.

Note:  All items arrive in a box unassembled.


  • Geissele Mk4 Federal 10" OD Green rail with laser etched T-markings
  • Daniel Defense 11.5" CHF 1:7 twist 556 NATO chambered barrel with chrome lining
  • Surefire FH556-215A Fast Attach 4-prong flash hider (this is an earlier model and will fit FA556 suppressor, but not the SOCOM generation suppressors) with DLC black coating
  • Troy low profile gas block with two bottom set screws
  • Remcon premium military contract carbine length stainless steel gas tube
  • Geissele barrel nut and bolts to attach
  • smaller Allen wrench for tightening Mk4 rail tabs
  • gas block roll pin for attaching the gas tube
  • Surefire indexed washers for attaching and timing the flash hider
  • Small Rockset tube to apply to barrel to attach the flash hider

Note:  See here for a similar offering with a Colt barrel:  FBI HRT barrel and Federal OD Green rail kit - Colt barrel