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The Mk17 Banshee and Radial Delayed Awesomeness

CMMG champions innovative AR designs in a market drenched in Stoner's famed rifle. They have revolutionized the AR platform with the Anvil, Mutant, and the topic of today's discussion, the Banshee. The Banshee utilizes a unique radial delayed blowback system. The Mk17 Banshee takes P320 magazines and joins a full stable of AR pistols and SBRs in the Banshee series.

What's Radial Delayed Blowback

CMMG designed the radial delayed blowback system used by the Mk17 Banshee to overcome the faults with traditional blowback designs. The radial delayed blowback system utilizes a proprietary bolt and chamber. The bolt lugs are angular and lock into the proprietary chamber. These angular bolt lugs lock into the chamber and do not unlock until pressure levels have dropped.

Traditional blowback weapons require either a heavy bolt, buffer, or spring to allow the pressure to drop for safe operation. Each of these systems creates downsides with the traditional blowback system, and blow operation guarantees excessive recoil. A 9mm PCC with a blowback system creates recoil similar to that of a 5.56 caliber rifle.

The CMMG Radial Delayed blowback system eliminates the ergonomic issues and recoil issues associated with a blowback design. Radial Delayed system does retain the reliability of a blowback-operated PCC. It just eludes the downsides of a blowback system.

Further Features of the Banshee Mk17

The Mk17 Banshee crams a lot of features into a very compact package. The Mk17 Banshee sports an ambidextrous safety made by CMMG. The gun's massive ambidextrous charging handle grants complete control over charging the weapon, clearing malfunctions, and shooters can even blade the charging handle into action should they so choose.

The Mk17 Banshee's magazine release ensures you can reach the release with your trigger finger for rapid reloads, or your nondominant pointer finger for reloads with retention. The Banshee utilizes both pistol magazines and incorporates a last round bolt hold-open device. The uncommon combination of an LRBHO device and pistol magazine makes the Banshee even better. The presence of an LRBHO increase the speed of your reload significantly.

CMMG equipped the weapon with their Ripbrace. This modified SBA3 brace instantly deploys to one of five preset positions. Tug it, and it slides precisely to where you want it each and every time.

Moving to the front of the gun and we see the short 5-inch barrel topped with ½ x 28 threads for muzzle devices and suppressors. The handguard wears several M-LOK slots for accessory mounting, and an integrated hand stop to keep your hands hole free.

Lastly, we got the Titanium cerakote finish. CMMG offers ten finish options for customers to choose from.

Radial Delayed Blowback – By The Numbers

To fully show the difference that the Radial Delayed system makes in controlling the weapon, it was set against the Micro Scorpion. The Micro Scorpion utilizes a traditional blowback system with a huge bolt. The Mk17 Banshee and Micro Scorpion competed under a timer in the very simple, but practical Box Drill.

A Box Drill requires two man-sized targets set one meter apart. The shooter fires two rounds into the chest of target one and then transitions to target two and fires two rounds into the chest. The shooter transitions upwards for a headshot on target two and finishes the drill by transitioning back to target one for a final headshot.

The drill was completed five times by each gun, and a Pocket Pro 2 timer was utilized to keep time. The Mk17 Banshee had an average runtime of 3.23 seconds. The Micro Scorpion had an average time of 3.48 seconds. An exact quarter second difference illustrates the difference the Radial Delayed system makes. It should be noted throughout testing, the Mk17 Banshee was run through the wringer and the overall best time for the Box Drill was 2.78 seconds.

Recoilmeter and Measurements

Drills present an interesting means to gather information, but the MantisX and it's Recoilmeter offers another means to collect information. The MantisX Recoilmeter measures a variety of factors, including muzzle rise and average recovery time. To ensure fairness, both guns utilized ammunition from the same box, with the MantisX attached to each weapon's handguard's bottom.


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The Mk17 Banshee had an average recovery time of .39 seconds, and the Micro Scorpion came in at .59 seconds.

The Banshee had an average muzzle rise of 1.47 degrees, and it beat the Micro Scorpion's average of 2.03 degrees. Keep in mind that the Micro Scorpion weighs 14 ounces more than the Banshee and weight benefits recoil reduction.

The Radial Delayed action makes a significant difference in how these two PCCs handle.

Down and Dirty with the Mk17 Banshee

CMMG produced the Mk17 Banshee as a premium grade firearm, and its performance reflects that. Downsides to the weapon's performance include the trigger. The trigger breaks at 7.5 pounds, and while heavy, the trigger presents a smooth and short pull. Lighter weight PCC triggers compromise reliability with the hard primers associated with budget ammunition. A heavier trigger gives shooters enhanced reliability among all ammo types.

The Banshee blazes through the aforementioned cheap ammo without issue. Steel cased cheap ammo from former Soviet Union states presents no problems in the reliability department. The Mk17 Banshee eats whatever ammo you put through it and smiles the entire time. The Banshee doesn't need constant attention from the AP brush or vast lubricant applications to run right either.

Pistol calibers work inside of pistol ranges, and while the Banshee grants shooters more precision, it can't grant the 9mm round much extra range. Inside of 50 yards, the Banshee owns its environment. Inside of 50 yards, the Banshee easily creates groups in the 1.5-inch range. Beyond 50 yards, things get wonky. At 100 yards, a shooter can hit a man-sized target but don't expect to split cards at that range.

The Banshee weighs a mere 4lbs and 10 ounces. The overall length hits 18.9 inches with the brace collapsed. The lightweight and short design combined with the low recoil radial blowback system make the Mk17 Banshee an excellent home defense weapon.

Home Defense Worthy

The Banshee bestows shooters with an ultra controllable weapon in a compact package. This type of weapon excels in close quarters combat type shooting. Designs like the Banshee give you a potent and very capable weapon platform for defensive shooting. Self-defense shootings in the civilian world occur well within 50 yards, so Banshee wielders aren't missing out on much. Pistol calibers can't stand toe to toe with rifle calibers, but only fools would ignore the lower recoil, concussion, and length advantages pistol-caliber weapons offer for home defense.

The Banshee works with shooters of any size and near any skill level. When a shooter graduates from the 22 LR, they'll easily transition to a gun like the Banshee. This weapon presents little intimidation factor for a new shooter. This includes young shooters who may not have the strength to safely wield a standard carbine.

Complaints and Gripes

The Banshee Mk17 costs nearly 1,500 dollars and while quality costs the Banshee lacks when it comes to opening the box. The Banshee comes with a single 21 round SIG Sauer magazine and no sights. At that price point, CMMG should include an extra magazine and some Magpul sights.

The Banshee Mk17 lacks compatibility with the SIG P320 ETS magazines, so that does reduce magazine compatibility and limits your capacity to 21 rounds until SIG produces a factory 30 round magazine. Factory SIG P320 magazines do break the bank compared to Glock magazines. The Mk17 Banshee broke the PCC mold and proved itself as a fantastic firearm, but CMMG could include some extras.

Off to the Races

The Mk17 Banshee just makes sense. The P320 dominates the modern striker-fired, polymer frame market. The weapon dominated the MHS competition, and all four military branches are adopting the pistol. The P320 and its variants have been a success in the police and civilian market as well. The P320 will be around for a long time, and hopefully, we'll see magazine capacities extend, and prices drop.

The Mk17 Banshee presents a big push forward for the PCC market, and the radial delayed system rules. Crowded describes the AR market perfectly, but CMMG found a way to change, adapt, and improve the design. For that alone, they deserve praise, but along the way, they also made a damn fine firearm.


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One response to “The Mk17 Banshee and Radial Delayed Awesomeness”

  1. Billy says:

    Meh. Call me when it takes Scorpion mags.

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