The Geissele Super Modular Rail MK4 (SMR) was designed as an ultra light weight rail system for the M4 Carbine and all mil-spec AR-15 variants. The SMR MK4 was designed to do a good job in meeting the ten design specifications for a good M4 weapon rail with an emphasis on weight reduction.
Instead of four sharp and jagged M1913 rails spaced at 90 degree intervals the SMR MK4 only has a M1913 rail at the 12 o’clock position while at 9, 3 and 6 o’clock the M1913 rail is abbreviated and is only present on the muzzle end. The remainder of the side and bottom positions have a flat structure that feels better in the hand than the
sharp and jagged M1913 rail sections.
2. SET-UP IS MODULAR AND FLEXIBLE
Most weapon accessories such as flashlights and visible lasers are
positioned at the muzzle end of a weapon rail. The SMR MK4 has M1913 rails toward the muzzle to accommodate the most frequently used positions for accessory mounting. There is also a QD mount at both the receiver and muzzle ends that accepts an industry standard QD swivel. An accessory 45 deg QD mount can be purchased so a sling can be secured at an upper 45 deg position if so desired.
3. FREE FLOATING
The weapon barrel is completely free floating when an SMR MK4 is mounted. No force is put into the barrel from slings or bipods that could effect point of aim.
The SMR MK4 is machined from a semi-billet extrusion made from aircraft grade aluminum. A semi billet extrusion is designed with
extensive machining stock for 3D features that are machined directly into the rail so that the rail is one integral piece.
Current infantry doctrine makes extensive use of accessories that require attachment to a weapon rail. Flashlights, visible and infrared lasers, night vision and thermal sights all require a rigid weapon rail so that zero is not changed when a bipod or sling is used to support the weapon from the rail. The SMR MK4 is a rigid interface for weapon
accessories due to its precisely machined proprietary barrel nut and secure rail interface and clamping arrangement.
Use of aircraft grade aluminum and high strength steels in the SMR MK4 give the entire assembly an excellent strength and performance to weight ratio. A 9.5" SMR MK4 weights 9.93oz. including the exclusive Geissele barrel nut and mounting bolts.
7. ACCESSORY RAILS EASY TO INSTALL
To save on weight, the SMR MK4 is not provided with accessory rails. The top M1913 rail and the machined in sections toward the muzzle are the only accessory mounting positions.
8. ACCESSORY RAILS ARE STRONG
The M1913 rails sections that are intended for accessory mounting are machined in directly to the rail body for an integral assembly.
9. RAIL ASSEMBLY IS EASY TO INSTALL
Each SMR MK4 comes with a precisely machined, 2-1/4” long
barrel nut that is machined from aircraft grade aluminum and hardcoat anodized for a durable surface. A combination wrench that will remove the stock barrel nut and install the Geissele one is also included. The Geissele barrel nut needs no indexing to the gas tube so installation
is a snap with just a torque value used for tightening. The rail is then slid onto the barrel nut and the precise barrel nut to rail fit precisely aligns the rail to the barrel. After indexing to the receiver rail two mounting bolts are tightened and the rail is secure.
10. RAIL IS EASY TO REMOVE
Just by loosening two screws and one of the indexing screws the Geissele SMR MK4 can be slid off the barrel nut for cleaning or gas system maintenance. Even a different rail with a different accessory configuration can be mounted. As quick as it is removed the SMR MK4 is can be re-installed with the precise barrel nut to rail fit
maintaining sight and accessory zero.