New Kid on the Block: CMMG’s Mk4, 22 Nosler Rifle

By Thomas Murphy, Photography by Jim Grant

The Company

CMMG was established 15 years ago, in 2002, by the Overstreet family—John, Jeff, Gretchen and Stephanie. Located in Fayette, Missouri, it is a leading manufacturer of AR rifles and related parts. Today, it manufactures over six different rifle and carbine versions of the AR platform. Calibers range from the 9mm pistol cartridge, through the .458 SOCOM, 7.62x39mm, 5.56 NATO, .300 Blackout and the powerful .308 Winchester. There are even five firearms chambered in .22 Long Rifle.

They produce all the parts needed to build an AR-type firearm. All of their products either meet or exceed original MIL-SPEC standards. They specialize in 22LR conversion kits for the AR that consist of either a 10- or 20-round magazine, .22LR bolt, forward assist adaptor, anti-jam charging handle and cleaning rod and jag.

CMMG even stocks provisions. The one that most interested this writer is “Tactical Bacon.” Yes, it’s bacon. Fifty-four slices of fully-cooked, ready-to-eat bacon in every CMMG-marked can.

The Mk4 V2, 22 Nosler

CMMG has come up with a new rifle—the MK4 V2 in 22 Nosler. It is unlike any of their other offerings, in that it’s chambered for the 22 Nosler cartridge. The AR-type upper and lower receivers are forged 7075-T6 aluminum. This aluminum alloy is very strong, with strength comparable to many steels. Its primary alloying element is zinc. This alloy has lower resistance to corrosion than many of the other aluminum alloys, but it is still very good; its composition is zinc, magnesium, copper and less than one percent of silicon, iron, magnesium, titanium and chromium. The T-6 temper has an ultimate tensile strength of 74,000–78,000 psi. There are four distinct models chambered for the 22 Nosler.

A 24-inch medium-taper fluted barrel is manufactured from 416 stainless steel, which is highly resistant to acid, alkali and fresh water. The tapered barrel is optimized for strength and weight. The muzzle has a step-down target crown. Its primary purpose is to provide propellant gasses a resistance-free path from all parts of the projectile as it exits the bore. Also, it aids in preventing muzzle damage, and it just plain looks good.

A CMMG RKM14 KeyMod handguard allows the installation of optics and lights. KeyMod is an interface system for mounting firearms components. It was designed in 2011 by Eric Kincel of VLTOR Weapons Systems located in Tucson, AZ. It has now been open-source released for use in the public domain.

KeyMod allows the operator to place MIL-STD-1913 rails wherever needed—even in a 45-degree position. The KeyMod system comprises two parts: the KeyMod slot and the KeyMod nut. The slot has a large diameter through-hole leading to a reduced width slot. The nut is stepped, with the larger diameter end chamfered around 270 degrees of its circumference. The angled face is intended to lock into the chamfer on the inside of the KeyMod slot. The two flats on the nut interface with the slot and allow both the mounted accessory and the KeyMod slot to be aligned without the use of tools to tighten the nut. The screw is swaged after assembly to ensure that it cannot back off the nut. The combination of the angled interface of the nut with the KeyMod slot and a recoil lug on the accessory make for a supremely strong attachment point that will not slip under rough conditions. This mounting procedure has an excellent return-to-zero when removed and re-installed.

Magpul provides the Magpul Original Equipment (MOE) pistol grip and MOE rifle stock; both made from a reinforced polymer with anti-slip texturing. The grip has a basic cap, but it can be outfitted with storage cores for gear storage.

A Geissele Automatics Super Semi-Automatic (SSA) trigger is installed in the lower receiver. It has a total pull weight of 4.5 pounds, with the first stage set at 2.5 pounds and the second stage at 2.0 pounds. There are no adjustments. The trigger is recommended for demanding applications, such as law enforcement, Close Quarters Battle (CQB) and mid-range carbine work. It is a semi-automatic version of their Super Select-Fire trigger.

Mk4 P, 22 Nosler

The Mk4 P rifle is equipped with a 22-inch, 1:8 twist, medium-taper 416 SS barrel. Its muzzle is crowned with a CMMG SV brake which is threaded ½”-28. As with the other 22 Nosler models, the receiver is forged 7075-T6 aluminum. The rifle’s total weight unloaded is 7.3 pounds. Its length is 42 inches. The buttstock is a Magpul MOE replacement for the AR15/M16 A1 and A2 rifle stocks utilizing the standard-length rifle buffer tube. It has an internal storage compartment accessible through a rear storage door. It does not need the A2 spacer for mounting. Its optimum shape provides for excellent offhand shooting positions. There are knockout plugs on the bottom that allow the addition of an accessory rail.

Mk4 RCE, 22 Nosler

The Mk4 RCE is fitted with an 18-inch barrel. The buttstock is a Magpul CTR stock with a six-position MILSPEC receiver extension. The overall length with the stock collapsed is 35 inches. Empty weight is 6.7 pounds. The Magpul CTR (Compact/Type Restricted) buttstock is a drop-in replacement for any M16/AR15 carbine using MILSPEC receiver extension tubes. The release latch is engineered to avoid snags, and the stock’s A-frame profile helps to prevent accidental extension. There’s a friction lock system that minimizes excessive stock shift and aids in rapid target re-acquisition. The rear of the stock has a 0.30-inch rubber buttpad to provide shoulder lock-up even when body armor is employed.

Mk4 S, 22 Nosler

The Mk4 S is the perfect rifle for hunting or punching paper targets. It’s the lightest of the four, coming in at 6.5 pounds. Its overall length with the buttstock collapsed is 34 inches. The rifle mounts an 18-inch barrel and has a standard M4 buttstock with a six-position MILSPEC receiver extension and an A2 pistol grip. Like the other three models, the barrel is 416 stainless steel and the receiver is forged 7075-T6 aluminum. With a scope of decent quality mounted, the Mk4 S would be a perfect choice for predator hunting.

History of the Nosler 22

The 22 Nosler is the smallest of the rounds offered by Nosler, the others being the 26 Nosler, the 28 Nosler, the 30 Nosler and the 33 Nosler, all based on the .404 Jeffery case that first saw the light of day back in 1905. The 22 Nosler is intended to be the most powerful .22 caliber cartridge that will function reliably when loaded in the AR platform. The 22 Nosler’s case capacity is 25% greater than that of the 5.56 NATO/.223, increasing its muzzle velocity by approximately 300 feet per second and its muzzle energy by more than 30 percent. All that is required to rechamber a 5.56 NATO rifle to the 22 Nosler is a barrel swap/new upper and a magazine change to a 6.8mm Remington SPC.

The 22 Nosler case is not derived from the similarly sized 6.8mm Remington Special Purpose Cartridge, and the 22 Nosler cannot be formed from the 6.8 SPC case. Also, the 22 Nosler has a rebated rim, whereas the 6.8 SPC is a rimless case. At 1.76 inches length, the 22 Nosler has the same case dimensions as the 5.56 NATO. However, the 22 Nosler case tapers from .420 inches at the extractor groove down to .400 inches at the shoulder, while the 5.56 NATO measures .378 inches and .354 inches. This results in an increased powder capacity and, consequently, a higher muzzle velocity of 3,350 feet per second and 1,370 foot-pounds of muzzle energy for a 55-grain bullet fired through an 18-inch barrel. By contrast, an equivalent 5.56 NATO bullet fired through a barrel of similar length has a muzzle velocity of 2,982 feet per second and 1,180 foot-pounds of muzzle energy. The velocity of the 22 Nosler at 100 yards equals that of the 5.56 NATO at the muzzle.

The 77-grain bullet in the 22 Nosler exits the barrel at 2,950 feet per second and has 1,488 foot-pounds of muzzle energy. It retains almost 1,000 foot-pounds of energy out to 200 yards.

Nosler’s 55-grain ammunition is loaded with its Ballistic Tip Varmint bullet. It has a polycarbonate tip that is driven back on impact, causing the bullet’s thin jacket to expand and fragment. The bullet’s boat tail base increases its ballistic efficiency.

The 77-grain ammunition utilizes a Nosler Custom Composition hollow point boat tail bullet that is capable of extremely uniform velocity and accuracy. The small meplat (flat or open tip on the nose of a bullet) improves the way the bullet travels through the air. Bullets of the same weight that have similarly shaped meplats will move through the air in a nearly identical fashion, making it easier to hit a target multiple times.

Care and Feeding

The Mk4 was fired with both Nosler Trophy Grade 55-grain Ballistic tips and 77-grain Match Grade Custom Competition ammunition. A Trijicon AccuPoint 2.5-12.5x was mounted on the Picatinny MIL-STD-1911 top rail. Both shooting sessions were interrupted by heavy rain, so the firearm got its baptism by water. From the initial shot, the rifle functioned flawlessly—no failure to fire, no stoppages, nothing. Accuracy at 100 yards was one ragged hole. The rifle is shipped with a 10-round magazine and comes with a CMMG lifetime warranty.

The only caveat expressed by anyone who has handled the rifle is that the 5.56 NATO rounds fit easily into the 6.8 SPC magazine, and the 22 Nosler rounds could be fed into the 5.56 NATO magazine. It is unlikely that the 22 Nosler would chamber in the 5.56 NATO; however, the gun could jam. The rebated rim would not let the extractor pick up the case. On the other hand, the 5.56 NATO could possibly be forced far enough into the 22 Nosler with the same results. For reasons of sanity, neither one of these actions was attempted.

This article first appeared in Small Arms Review V21N10 (December 2017)
and was posted online on October 20, 2017


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