null

Mk18 CQBR Upper Receivers

Mk18 CQBR Upper Receivers — 10.3" SBR Upper Groups

The Mk18 CQBR (Close Quarters Battle Receiver) is the 10.3" short-barreled upper receiver group developed at NSWC Crane for Naval Special Warfare. Paired with a standard M4A1 lower, it produces the Mk18 — the primary carbine of DEVGRU and a standard CQB weapon across NSW, MARSOC, and select SOCOM units.

Charlie's carries Mk18 upper receiver groups from Daniel Defense, Colt, Geissele, LMT, and KAC — including Mod 0 (with the Mk18 FSB / KAC RIS), Mod 1 (DD rail or equivalent), and the current Geissele URGI-style 10.3" configuration. Both factory and clone-correct custom-built URGs are available. These upper receivers drop directly onto any Mil-Spec M4/AR-15 lower receiver.

What is the difference between Mk18 Mod 0 and Mod 1?
The Mk18 Mod 0 uses the KAC RIS quad rail handguard (same as Block I M4A1) and a standard 10.3" Colt barrel with FSB. The Mod 1 replaces the KAC RIS with the Daniel Defense 10.3" rail — the same DD M4A1 RIS II used on Block II, adapted to the 10.3" length. The Mod 1 is the more commonly seen configuration in post-2010 NSW photography. Current configurations increasingly use the Geissele Mk16 handguard in the URGi-Chop-Boss pattern.