CMMG Mk 4 RCE: Prime example of a Recon I Recce AR

CMMG Mk 4 RCE: Prime example of a Recon I Recce AR


ABOVE: The RCE is CMMG’s version of a “Recce” or Recon AR. The driving force behind the Recon was to give sniper/observer teams a support weapon with greater range, lethality and precision than the issue M4 carbine. The Recon AR is lighter than a pure precision AR rifle and more likely to be used for a variety of missions besides sniping.

There can be little debate over the excess of AR style rifles currently flooding the marketplace – it is definitely the heyday of the AR platform. With so many manufacturers offering so many styles of AR rifles it is inevitable that different classifications of ARs would emerge to help distinguish intended roles. The CMMG Mk 4 RCE rifle evaluated herein is an excellent example of this trend. The RCE is CMMG’s version of a “Recce” or Recon AR.

Most attribute the Recon AR concept to the U.S. Navy SEALs dating back prior to the 9/11 attacks. The SEAL’s objective with the Recon AR was to give sniper/observer teams a support weapon with greater range, lethality and precision than the issue M4 carbine. The Recon AR is often confused with the SPR (Special Purpose Rifle) AR. The SPR began initially as an upper receiver upgrade to issue M16 rifles turning them into designated marksman or precision rifles with suppressor use the norm. In fact, SPR originally stood for Special Purpose Receiver before a complete SPR class of ARs emerged. The Recon AR is lighter than the SPR and more likely to be used for a variety of missions besides just precision interdiction most associated with SPR type ARs.

The CMMG RCE’s 14 inch KeyMod forend rail dominates its aesthetics. BUIS iron sights and a Weaver Tactical scope were easily installed. Magpul CTR buttstock and pistol grip comprised the other furniture aspects.

As is prone to happen, civilians quickly recognized and copied the Recon’s attributes. For civilians, the Recon AR was viewed as a multi-purpose ubiquitous weapon with a flat-top upper receiver for easy mounting of a variety of optics and 16-18 inch free-floated medium profile barrel with 1:7 or 1:8 twist surrounded by a forend rail system. One key Recon aspect is to minimize weight and keep the weapon’s profile sleek for better handling while offering superior accuracy and longer range terminal performance than shorter barreled ARs. Recon type ARs are required to be equally at home in CQB encounters characterized by multiple rounds fired rapidly with distances measured in feet while still offering precision fire out to 350-400 yards.

It is nice to witness a company and its products evolve over time. The CMMG Mk 4 RCE AR is a great example of this. Nearly twelve years ago, CMMG was established as a family owned business and remains so today. CMMG quickly made a name for itself as a respected builder of AR rifles and their models span the gamut of price and mission set up. One of the distinguishing CMMG practices is that every part used in their rifles are all 100% USA made, either manufacturing its own components or has them created to their own specifications. An example of this are the barrels used that start as blanks with CMMG taking them from there. All CMMG rifles are assembled in house.

The specific AR model evaluated for this article is the recently introduced Mk 4 RCE chambered in 5.56mm. It is one of the lighter AR versions on the market, especially considering that it features a full length rail, and weighs less than 7 pounds. A minimalist CMMG RKM KeyMod rail design measuring 14 inches defines the CMMG RCE’s aesthetics. The CMMG RKM rail system permits the barrel to be free floated. Not all weapons need rails and an array of accessories to be considered viable. While reliability should never be compromised in terms of cost/performance ratios, other items considered a must for some may not be high priority or worth it for others. KISS (Keep it Simple Stupid) methodology can pay dividends in terms of budget and allowing for concentration on other priorities such as training for example. The CMMG RCE shows versatility in satisfying customer needs by not using full length quad rails, but instead a lower profile handguard with adjustable KeyMod Picatinny rail sections. The minimalist approach for rails still allows plenty of room for VFG, bipod and lights/lasers if so needed.

The well balanced CMMG RCE keeps the muzzle on target even when rapidly fired shots are sent downrange. The CMMG SV muzzle device is part of the equation in this aspect as well.

Unlike many competitors, CMMG lists all the specifications for the components used in their different model ARs making gathering details on the RCE for this article as simple as looking at their website. The RCE’s 16 inch 1:7 twist 416 matte stainless steel medium barrel features M4 style feed ramps and employs a mid-length gas system with the direct impingement. CMMG’s own SV muzzle device is threaded on the barrel. The CMMG RCE is built upon forged 7075-T6 upper and lower receivers, with the upper featuring a full length rail that transitions into the rail along the top of the RKM rail. The upper is equipped with a standard forward assist and case deflector as well as an ejection port dust cover. Iron sights are not included giving the user the opportunity to install their own choice of BUIS (Back Up Iron Sights). A Magpul MOE trigger guard and pistol grip is used as is a Magpul CTR collapsible buttstock fitted over a mil-spec buffer tube. CMMG decided to upgrade the RCE’s trigger by installing a Geissele SSA. With accuracy an important part of the RCE’s mission statement, this is an important attention to detail. Overall length of the RCE is 36 inches with stock extended and 32.75 inches collapsed.

As mentioned earlier, short KeyMod sections of rail can be moved as desired to numerous positions around the hand guard, removed, or more sections added, depending upon the user’s preference. The KeyMod sections are readily available for purchase from a variety of sources. The KeyMod rail was designed by VLTOR and now open sourced to the industry. The KeyMod rail design is going to bring about a new generation of accessory mounts and furniture that connects directly to the hand guard instead of needing a rail surface to clamp onto. All of this keeps the overall rifle package lighter and more compact. The KeyMod system consists of two parts; the KeyMod slot and the KeyMod nut. The slot is distinctive with a larger diameter through-hole combined with a narrow slot. The slot is chamfered on the backside while the through hole is sized for clearance of a quick-detach sling swivel. The angled face created is meant to interface with the chamfer on the backside of the KeyMod slot. The full diameter is left intact to create two flats on the nut that align the nut to the slot, and allow it to be indexed to the accessory as well as to the KeyMod slot. The spacing of the holes is critical and is based on Mil-Std 1913 spacing to allow the greatest modularity with existing accessories. The combination of the angled interface of the nut to the KeyMod slot and the recoil lug to the through hole make for a very strong attachment point which will not slip under harsh recoil or counter recoil. It also provides for an excellent return-to-zero when removed and re-installed. KeyMod rail accessories include Picatinny rail sections, hand stops, vertical forward grips, bipod interface, light mounts, sling mounts etc.

Extreme Beam Tactical light mounted easily to the KeyMod forend via Picatinny rail section.

CMMG’s thought process for the RCE was to create a lightweight, simple to operate AR rifle similar to Eugene Stoner’s original direct impingement concept for the AR. This counter-intuitive approach involves maximizing the AR’s effectiveness and potential by simplifying it away from current trends of 10 pound quad rail rifles festooned with lights, lasers, designators, night vision optics, etc. The RCE utilizes AR improvements as long as items contribute to effectiveness. The fact that short sections of Picatinny rails are mountable on the KeyMod handguard gives a nod to realism that high intensity flashlights serve a role and have a place on a fighting rifle. An Extreme Beam SX21R Ballistic tactical light was affixed to a KeyMod section on the left side of the forend via a 1 inch Weaver style scope ring. The Extreme Beam SX21R offers 220 Lumens of light in a recoil resistance body weighing only 5.58 ounces. A pressure sensitive switch is available, but was not used as it is a simple matter to active the switch via thumb. The military and better equipped federal agencies have gone away from tactical lights due to use of night vision; however, the tactical light still has a place in the tactical realm, especially for civilians and law enforcement.

A Weaver Tactical 1-5x with Illuminated MDR Reticle was used with the CMMG RCE. The Weaver Tactical 1-5x is designed for instinctive, close-range/low-magnification situations with variable intensity red or green illuminated reticle, yet allow shooters to engage targets with greater precision at longer ranges thanks to the 5x. The Weaver Tactical 1-5x scope will strike many as unconventional in terms of commonly associated optics on a military style rifle. However, for law enforcement, civilian or private security contractor it is worth consideration as it supplements the CMMG RCE’s performance flexibility. The RCE mated to variable power Weaver optic is able to handle diverse roles whether close range engagements or further engagements per the Recon/Recce job description. The concern for operating the magnified Weaver Tactical in a CQB environment is quelled once one becomes familiar with the Bindon aiming concept. Human vision is based upon a binocular (two eyes) presentation of visual evidence to the brain. The addition of a bright red or green dot in the center of the cross-hairs makes it very easy to keep both eyes open, especially at 1x power setting. Even if using a higher power setting the brain merges the two images. During dynamic movement, the scene through the telescope blurs because the image moves more rapidly due to magnification. The one eye sees the bright dot against the blurred target scene, so the brain picks the scene from the unaided eye. The shooter swings the weapon towards the target while perceiving the dot indicating where the weapon is pointed. As soon as the weapon begins to become steady in the target area, the brain switches to the magnified view.

Ammunition tested with the CMMG RCE was a combination of Black Hills Ammunition loads, multiple Hornady TAP loads, and Federal offerings with an emphasis on premium heavier 5.56mm/.223Rem. loads. This was a nod to requirement of better long range performance as defined in the Recon’s mission statement. Federal 55 grain and 62 grain FMJ was used during CQB type drills; an affirmation to basic economics in terms of ammunition costs. The CMMG RCE rifle kept all loads tested at 1.5 inches at 100 yards with Black Hills 77 grain OTM, Federal Premium Match 69 grain, and Hornady 75 grain Match producing sub-MOA groups. This accuracy was obtained with the 5x setting on the Weaver Tactical scope. The CMMG RCE produces accuracy that fully supports the Recon/Recce’s defined role. Accuracy test protocol consisted of three five-shot groups with each ammunition type; group sizes were averaged. Velocity figures ranged from 2,600 to 2,800 feet per second over a RCBS chronograph.

Not all weapons need rails and an array of accessories to be considered viable. A light weight, fast handling rifle such as the CMMG RCE is a premium when having to react to a threat.

The CMMG RCE was evaluated at Echo Valley Training Center (EVTC). The layout and availability of various steel targets and simulated barricades at Echo Valley Training Center are convenient for allowing full spectrum firearm evaluations. The RCE was used within the 100 yard bays at EVTC firing from barricades and engaging multiple targets, prepared firing position line with targets placed out to 300 yards, 360 Range, and EVTC’s Jungle Walk range. Numerous drills were run involving magazine changes and moving between barricades simulating cover. Steel silhouettes were situated randomly from 20 to 110 yards. The CMMG RCE made short work of striking targets in quick fashion. Targets were engaged five times each starting from the standing, moving to another locating, five more rounds from kneeling, and finally moving yet again and transitioning to the prone with five more rounds reloading as necessary. The rifle was then fired supported via bipod or pack and proved just as efficient against a fluid drained automobile located at EVTC with steel popper targets located inside the cab. A High Speed Gear (HSG) patrol belt configured with their “Taco” magazine pouches was used to support the RCE. The HSG magazine pouches do not compromise retention for the sake of convenience.

ARs can be had in everything from piston-driven varieties, multiple calibers, pistol configurations, flattops, and various barrel lengths. The inherent modularity of the AR is its greatest attribute for adapting to individual preference; whether it is for competition, target shooting, military and law enforcement, or personal defense. This same adaptability can also lead individuals astray as to what is necessary versus desired in setting up a defensive rifle. Not all weapons need rails festooned with an array of accessories to be considered viable. The ability to mount infrared laser designators, night vision devices, or other sorts of tactical hardware is not something most of us require in a fighting rifle.

The AR platform seems to be coming full circle in terms of returning to a sleeker more svelte form. The Recon/Recce AR as epitomized by the CMMG RCE is an excellent example of this. The benefit of the CMMG RCE’s lighter weight, yet superior accuracy, is hard to deny. A light weight, fast handling accurate rifle is a premium when moving dynamically during training evolutions and the CMMG RCE represents such a rifle.

The CMMG RCE is a direct impingement Recce/Recon type AR.



Echo Valley Training Center

Weaver Optics

Weaver Tactical 1-5x optic was mounted with a Weaver scope base on the flattop RCE upper. The CMMG AR was evaluated with multiple ammunition types with an emphasis on heavier 5.56mm loads. The Federal American Eagle 62 grain Fresh Fire Packs are relatively new on the market.

The CMMG RCE displayed a high degree of accuracy giving it the capability to perform at longer distances if needed to be deployed as a DMR.

A High Speed Patrol Belt affixed with their TACO magazine pouches supported evaluation of the CMMG RCE.

The CMMG RCE was used within the 100 yard bays at EVTC engaging multiple targets.