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Daniel Defense DDM4 PDW Review

Daniel Defense ventures into the personal defense world with the new DDM4 PDW.

Daniel Defense DDM4 PDW Review
Photo by Mark Fingar

Anyone interested in a firearm for personal defense should consider Daniel Defense’s new DDM4 PDW. While it certainly looks unconventional for a pistol, the PDW has a number of features that make it suited for home defense and concealed carry while still maintaining all the legal protections of a pistol. Anywhere you can legally carry a concealed pistol, you should legally be safe to conceal the DDM4 PDW.


There is no substitute for a good rifle when faced with potential violence. Once shouldered, a two-­handed long arm provides better stability over a smaller handgun resulting in a higher hit probability. If it is chambered in a rifle-­pressure cartridge, terminal effects are often more effective at stopping a threat than anything fired out of a conventional pistol. The DDM4 PDW falls into the category of being a pistol chambered for a rifle cartridge.

Daniel Defense DDM4 PDW
The maxim defense CQB pistol brace is adjustable and highquality. It’s built on the same housing as maxim’s CQB stocks. (Photo by Mark Fingar)

The DDM4’s most compelling feature is its Maxim Defense CQB pistol brace — a $375 value — which can be used for additional support when firing with one hand.

Many ask whether or not it’s legal to rest an arm brace against the shoulder when firing. The Bureau of Alcohol Tobacco and Firearms’ (ATF) last ruling dated March 21, 2017, states,

“To the extent the January 2015 Open Letter implied or has been construed to hold that incidental, sporadic, or situational ‘use’ of an arm-­brace (in its original approved configuration) equipped firearm from a firing position at or near the shoulder was sufficient to constitute a ‘redesign,’ such interpretations are incorrect and not consistent with ATF’s interpretation of the statue or the manner in which it has historically been enforced.”

You cannot be thrown in jail for firing the DDM4 PDW from the shoulder unless you alter the arm brace in some way. However, any alteration will likely be construed as a “redesign” and end badly for the owner. With all the legalese out of the way, that leaves us happy consumers with a PDW chambered in a great cartridge that is legally allowed to make “incidental, sporadic, or situational” contact with the shooter’s shoulder.

The Blackout

The .300 Blackout (BLK) is a cartridge ideally suited for defensive purposes. It has a Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) maximum pressure of 55,000 pounds per square inch (psi), a common ceiling for many rifle rounds. However, the .300 BLK case is full of pistol powder. This combination makes for some interesting internal and external ballistics.

There isn’t much room left for powder in the .300 BLK case when those big .30-­caliber bullets are seated in place, especially when shooting 188-­ to 220-­grain subsonic projectiles. The lack of volume requires use of a powder that doesn’t take up much space, so pistol powders are preferred. The two best, in my opinion, are Hodgdon’s H110 and CFE BLK. (The latter is H110 with some neat powder coatings.) Both powders produce excellent velocity out of the .300 BLK while staying below maximum pressure.

The amount of powder in the case will determine how fast the bullet will potentially fly. High-­powder volume equates to high-­gas volume once the powder ignites, and lots of gas volume is necessary for high velocity. The .300 BLK does the best it can with limited powder volume, and it gets very good velocity with the tiny amount of powder each round uses. The huge advantage the pistol powder brings to the .300 BLK is its ability to burn completely within just a few inches of barrel.

Chambering the DDM4 PDW in 5.56 NATO would make little sense. The slower-­burning rifle powder is nowhere near completely burned in short barrels by the time the bullet leaves the muzzle. With SBRs in 5.56, there is always lots of muzzle blast and flash to consider. The complete burn of the .300 BLK means that there is little blast or flash when the bullet exits the muzzle, even from a 7-­inch barrel. This makes the DDM4 PDW ideal for home defense or use in or near vehicles because it offers rifle performance with a pistol’s muzzle blast and flash. If you’ve ever shot a gun indoors, the advantages of this feature cannot be overstated.

Daniel Defense DDM4 PDW
The linear compensator takes all the muzzleblast and directs it downrange, away from the shooter. (Photo by Mark Fingar)

The low exit pressure of the .300 BLK (thanks to the use of powder that burns completely in its short barrel) makes shooting the DDM4 PDW pleasant. It is also an excellent choice for a suppressor, and (most of the time) a pistol suppressor is perfectly usable on any .300 BLK for the aforementioned reasons.

Daniel Defense managed to put all of this performance into a package that only measures 203/4 inches in overall length. Even with a suppressor in place, the DDM4 PDW is compact and easily maneuverable. Should a home invasion occur, I can’t think of a better defensive firearm choice than this PDW with a light and suppressor attached. Should it make incidental contact with the shooter’s shoulder, it’ll shoot just like a rifle and produce similar effects.


Daniel Defense DDM4 PDW
The upper receiver is so short that it comes equipped with a removeable hand stop to prevent the shooter’s hand form getting too close to the muzzle. (Photo by Mark Fingar)

PDW Deets

Getting an overall length of 203/4 inches for an AR-­pattern pistol is no easy task. Choosing to chamber it in .300 BLK is a wise choice considering the barrel is only 7 inches long. The 7-­inch barrel is long enough to get 110-­grain bullets above 2,000 feet per second (fps), so it has good muzzle velocity. If the barrel were any shorter, the velocity would dip below 2,000 fps and reduces the terminal effect of any bullet.

Daniel Defense makes the barrel on the PDW by hammer forging it on a mandrel that forms the 1:7-­inch twist rate into the bore. Hammer-­forging a barrel makes it more durable than any other manufacturing method, so the PDW’s barrel will last well past 10,000 rounds. The 1:7-­inch twist rate matters because it’s fast enough to stabilize subsonic rounds while remaining slow enough to keep the expanding subsonic rounds from opening up inside a suppressor, should the owner choose to mount one on the PDW.

Daniel Defense DDM4 PDW
The DDM4 lower receiver features a slightly flared magazine well that makes reloads easy to execute. (Photo by Mark Fingar)

The PDW has a short pistol-­length direct-­impingement gas system, so it will function with both supersonic and subsonic rounds, even when unsuppressed. The .300 BLK cartridge is suppressor-­friendly, thanks to its low exit pressure. However, not every PDW owner will have a suppressor and still might want to shoot subsonic rounds. Shooting subsonic rounds out of an unsuppressed DDM4 PDW makes sense if the owner lives in a state where suppressor use isn’t allowed, or doesn’t have the money for a suppressor, but still wants as little muzzle blast as possible. This is a typical home defense scenario and the DDM4 PDW would do well in it, especially when loaded with Hornady’s new 190-­grain Sub-­X load. Daniel Defense affixes what they call a “linear compensator” to the PDW’s muzzle to direct all muzzle blast downrange. It functions as advertised and is threaded onto the muzzle with a 5⁄8-­24 pitch, so it is easily removed for use with a suppressor.

The forend Daniel Defense attaches to the PDW is 6 inches long and covered in M-­Lok slots. Both the barrel and handguard length are ideal for defensive use. The barrel is long enough to get light bullets above 2,000 fps, and the handguard is long enough to mount a light while still leaving some space for the support hand.

Daniel Defense DDM4 PDW
Photo by Mark Fingar

As mentioned, the Maxim Defense CQB Pistol Brace is a defining feature of the DDM4 PDW. The arm brace portion of the device is made from hard rubber surrounded by a Velcro strap. The brace is able to be wrapped around the shooter’s arm and held in place with the Velcro strap, or can make incidental contact with the shooter’s shoulder, giving it similar function to a buttstock. Should it make contact with the shooter’s shoulder when firing from the prone or from a bench, the brace has a small toe and doesn’t ride a rear bag very well.

The CQB Pistol Brace is well-­made and shows every sign of being rugged. While some arm braces have a cheap feel, this one oozes quality. There is a small steel locking plate with a tab on the left side of the brace that, when depressed, allows for brace extension. That steel plate locks into the two steel rods that connect to the rubber brace. The use of steel makes the entire brace assembly robust and worthy of duty use.

Since the DDM4 PDW is a pistol with an arm brace, there is no way to mount a sling to the rubber brace. However, there is a small tab the extends below the buffer tube that serves as a single-point sling mount. This allows the shooter to go hands-free in defensive scenarios to open doors, make phone calls, etc.

Burning Powder

Daniel Defense DDM4 PDW
The bolt carrier group is made to military specifications. The bolt is made of Carpenter 158 steel, and the carrier is of 8620. (Photo by Mark Fingar)

The upper and lower receivers, and what’s inside them, are what Daniel Defense is known for. Everything in the bolt carrier group meets or exceeds military specifications. Both receivers are forged from 7075 T6. Finish work is flawless.

Daniel Defense makes a grip with an integral triggerguard that will leave no blisters on the shooter’s hands. It has a seamless and smooth transition from triggerguard to grip that’s very comfortable.

Daniel Defense DDM4 PDW
Daniel Defense’s ergonomic pistol grip features a soft-touch overmolding texture and integral triggerguard. It sells for $31. (Photo by Mark Fingar)

I focused my efforts when accuracy testing on supersonic rounds. My experience when accuracy testing subsonic rounds at 100 yards was that group sizes increased by 50-percent or so. The best group of came from using SIG Sauer’s 125-grain Match ammunition with five shots grouping 1.56 inches. Given the standard AR trigger and the rubber stock with a narrow toe, I’d call that good. Average group size for all loads was just more than 2 inches.

Daniel Defense DDM4 PDW
Notes: Accuracy is the average of five, five-shot groups at 100 yards. Velocity is the average of five shots across a LabRadar chronograph placed adjacent to the muzzle.

The DDM4 PDW is an excellent defensive firearm that can be legally concealed like any pistol. It makes an ideal travel companion. The fact that it packs the punch and range of a rifle makes it even more attractive.

Daniel Defense DDM4 PDW Specs

  • Type: Direct impingement, semiautomatic
  • Cartridge: .300 BLK
  • Capacity: 20, 30 rds.
  • Barrel: 7 in.; 1:7-in. twist, CHF
  • Overall Length: 20.75 in. (collapsed); 24.75 in. (extended)
  • Weight: 5 lbs., 7 oz.
  • Finish: Hardcoat anodized
  • Arm Brace: Maxim Defense CQB Pistol Brace
  • Forend: DD 6-in. MFR XL
  • Length of Pull: 8.5 in. (collapsed); 12.5 in. (extended)
  • Sights: None
  • MSRP: $1,865
  • Manufacturer: Daniel Defense, 866-554-4867, 
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