Range Report: SIG Sauer MPX-PSB — Next Generation Civilian PDW

SIG MPX-PSB pistol left profile

In military and LE circles, a PDW (Personal Defense Weapon) is a compact, select fire weapon that falls somewhere in-between a submachine gun and an assault rifle. In civil terms it means a semi-automatic vision, more than likely with a pistol with a brace. It means a SIG Sauer MPX-PSB.

SIG MPX-PSB pistol right profile
The MPX-PSB is based on an AR-15-style platform, except it uses a closed, fully-locked short-stroke, pushrod gas-operated mechanism.

The SIG is a tactical-looking weapon because it has a military/LE weapon ancestry that is especially noticeable due to the magazine mounted in front of the trigger guard and not in the grip. Initially, there is an awkwardness shooting pistols such as the SIG MPX. It feels like an SBR (Short Barrel Rifle), yet it does not have a stock for a steady aim. The SIG MPX requires a two-hand hold—very different from a typical handgun. I’ve put in a lot of range time with braced pistols, and fully believe proper training and time is all that is needed to master these large pistols. The SIG also uses a short pushrod gas system.

The MPX-PSB is based on an AR-15-style platform, except it uses a closed, fully-locked short-stroke, pushrod gas-operated mechanism. If you are an AR shooter, you will quickly adapt to the SIG, since controls and handling are similar.

The MPX-PSB is built with an upper and lower receiver, so take down is similar to an AR-15. In the lower, the bolt release, magazine release, and safety selector are ambidextrous and easy to manipulate. The lever and button “touch surfaces” are finely serrated. It is equipped with SIG’s comfortable pistol grip with textured side panels and coarsely serrated front and rear straps.

SIG MPX-PSB pistol left profile
The bolt release, magazine release, and safety selector are ambidextrous and easy to manipulate.

The magazine well is well flared to suck in the translucent magazine. The magazine was easy to load—even to the 30th round—and had a pebble texture on the sides with serrations on the front and rear edge. Not enough to snag in a mag pouch, but enough for a sure grip. It also had metal feed lips.

The trigger guard is oversized and glove friendly. The rear of the lower has a quick detach socket and a small rail to attach a brace. The trigger is single stage and broke at about seven pounds on average.

The upper offers 14 inches of top rail where the folding front and rear sights attach. The sights deploy and fold without pressing a button. A detent keeps them up or down.

There are two rear apertures, which are adjustable for windage. The front sight is a post-adjustable for elevation. It is protected by wings. Since buttons are not required to deploy or stow the sights, the sights can easily fold back—if the weapon is accidentally dropped.

SIG MPX-PSB pistol controls
The SIG’s controls are layed out similar to an AR-15.

The KeyMod handguard allows the user to mount accessories on five different rails. A hand stop is mounted behind the muzzle. The barrel is free floated and capped with an A2-style flash hider that can be removed to add your choice of muzzle device. The eject port is sized to fit a 9mm round and includes a dust cover. The SIG uses an oversized charging handle similar to an AR-15. Charging the weapon was as easy as nearly any AR-15 pistol. The SIG was easy to disassemble and clean—just like an AR-15.

At the range, the SIG showed some excellent accuracy. With Aguila 115-grain FMJs, my smallest group measured 0.54 inch. The other ammo brands were just slightly larger. On average, I found the SIG capable of 5-shot groups under one-inch. A red dot or reflex sight would shrink groups even more, but these are good iron sights and optimal for the distance most likely to be used with the pistol.

SIG Sauer MPX-PSB, 9mm, MSRP: $1,700
Action Type Short-stroke pushrod gas system
Overall Length 16.85 in.
Overall Length w/ Brace 25.75 in.
Overall Height 11.0 in.
Maximum Width 2.0 in.
Weight Unloaded 6.0 lbs.
Weight Loaded 6.8 lbs.
Upper Receiver Forged 7075-T6 aluminum
Lower Receiver 7075-T6 aluminum
Barrel 8.0 in., 1:10 Twist
Muzzle Device A2, 13.5×1 LH Threads
Pistol Grip SIG AR-style
Handguard SIG aluminum KeyMod
Magazine (1) 30-round polymer
Rear Sight Steel, folding, Windage Adj.
Front Sight Steel, folding, Elevation Adj.
Trigger 7.0 lbs.
Safety Ambi., 2-Pos. Lever
Limited Lifetime Warranty
Made in USA

I ran the SIG with and without the brace. The nice feature of the SIG is the brace can be folded out of the way. The pistol can be fired with the brace folded or extended. Reloads were fast, since the SIG had a gaping mag well. The bolt locked back on last round fired. Inserting the magazine with my support hand, and slapping the bolt release button with my support hand thumb, was smooth and fluid. The polymer of these magazines seemed to be slicker against the metal.

All controls worked with authority and ease. I got into a nice rhythm with the SIG, grasping the handguard like I would on an AR-15. I ran the SIG hard firing one and two handed, on its side, and upside down. No jams of any kind were experienced

The SIG is well built—tight with no wiggle. Recoil was very manageable. The SIG MPX is next gen civilian PDW.

Do your own an AR pistol? Do your carry it? DId you get it for a specified purpose or just for fun? How does it perform? Share your answers in the comment section.

The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (7)

  1. Thanks for the write up. Probably a slick little piece.
    I kinda have to agree with our friend, 70’s ops though. I did a similar thing with a 10.5 inch barrel in 5.56. Good iron sights on it and I have zero issue out to 100m ( that’s as far as my local spot will let me shoot) but I have no doubt it’s good past that. Then, with a quick swap, I have a 16 inch in .458 for thumpin behind light obstacles. As far as 9mm… my M9 is about as good as anything. Or my glock.
    Also, this thing weighs 6 lbs empty??? What’s it made out of? I mean I have a 16″ A4 type under 6 pounds.
    Lastly, and I’ll shut up. For a PDW, I really am looking at the whole picture. That includes reliabilty and parts interchangeability.

  2. Is sig ever going to keep their word and make the 40 and 357 sig conversation for this? I would say nope, just a lie to get a bunch of us to buy this!

    Sig needs to keep their word and make what they promised over 3 years ago.

  3. For that price, why not buy 2 CZ Scorpions?
    A pistol and a carbine!
    Or how about a Scorpion and a silencer?
    With money left over for the tax stamp!

  4. Hey Robert, nice article.
    From early 2015-mid 2016, I put together a 10.5″ SBR, which could be run as a pistol, with just a stock to blade change. It took so long because I’m a cheap old man LOL. I patiently waited for parts to be available at what I thought was a good price. I wound up with Anderson RF-85 hard parts and Zahal/Mako IDF style furniture. Its perfect.
    I built it with the intention of having a weapon I could keep shouldered, and spin in a hallway without having to change my sight picture or pull the weapon down.
    What I wound up with is an extremely dependable, very accurate, tiny AR. After the addition of a 3-9×42 scope, I have absolutely no trouble outshooting most everyone that frequents the range I go to. All the targets are 150 meters and under, but I’m confident out to 200 easily. It has turned out to be a very fun little AR.
    I’ve never had an issue with it cycling, it cleans up with soap and water. Requires NO lubrication and is very fast. I’m really not a “grouping” kind of guy, but at 150 meters I have no problem keeping all my shots inside a standard 2″ bullseye.
    The best thing about it, is in under 20 seconds, I’m sending 6.5 grendel rounds down range with just an upper and mag swap. Keeping me deadly accurate from point blank CQB to well past 1000 meters.
    Oh, incidentally, without the scope, I have just under $300 into the SBR setup. Patience pays off. Several “impatient” friends have spent up to 5 times what I have, on all sorts of “big name” RTS AR’s. I make them feel terrible, shaking their heads, adjusting things and making excuses. That’s the best part. The OLD man with his “budget gun” kicking their asses. Ahhhhh, that cheap, old, special forces guy wins again.

    As always
    Carry on

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