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SIG Sauer Copperhead Pistol Review

Is SIG Sauer's Copperhead the step up in a CCW pistol you have been looking for?

SIG Sauer Copperhead Pistol Review
SIG Sauer’s new MPX Copperhead pistol is a highly specialized tool designed for low profile discreet carry when you want a bit more than your CCW pistol can provide and a carbine is simply too big.

Is your concealed carry pistol enough? Maybe you EDC a .380 auto, a single-stack 9mm or something like a Glock 19 but would like the option of having “a bit more” available if you need it. Something you can carry in addition to, not as a replacement for your daily concealed carry pistol. This is a key point. Basically what some will refer to as a Personal Defense Weapon (PDW) and I simply call a “bag gun”. The intended purpose for it is to provide a higher hit probability, especially at distances beyond 15 yards than your pistol. You might also desire an increase in terminal performance, barrier penetration and improved exterior ballistics over a handgun. All the while remaining relatively small, so you can carry it discreetly in say, a messenger or sling bag.

It wasn’t too long ago the notion of discreetly carrying a long gun or AR pistol as you went about your day would have you labeled as “a bit out there”. Times change, and today more and more lawfully armed citizens are considering having something available in addition to their handgun, just in case. This might be an old pump shotgun kept in the pick-up or a cased AR-15 pistol behind the seat of their car. For others it might be a back-pack with a broken down AR, pistol caliber carbine (PCC) or some other firearm they can grab and bring with them on certain occasions. Something to provide a bit more peace of mind to ensure their family is safe.

SIG Sauer Copperhead Pistol
Face it, things are getting worse rather than better, having a piece like a Copperhead you can discreetly carry if you so desire is a smart option to have.

One option to consider is SIG Sauer’s 9mm Parabellum MPX Copperhead pistol. This is a visually eye-catching piece intended to be very compact facilitating discreet on or off body carry. The Copperhead is a commercial semi-automatic pistol version of a selective-fire submachine gun designed for a military project. It was developed for end-users requiring more performance than a service pistol is capable of providing, while being significantly smaller than a 10.5 inch M4 based carbine. It is similar in concept, and size, to an MP5K PDW. I’m not going to delve into the submachine gun design developed for Government use, but will rather focus entirely on the commercial Copperhead model’s suitability for use by lawfully armed citizens.

SIG Sauer Copperhead Pistol
The 9x19mm is not as desirable as a rifle caliber, but it’s economical to practice with and will get the job done with careful load selection. L to R: 9mm, 5.56mm, 7.62x39mm, 300 BLK super and subsonic, 9x39mm.

If you desire to have a step-up in performance over your carry pistol there are a few things to consider. While the most obvious answer would be to simply “get a rifle”, it may not be that straightforward. This may be due to laws in your locale, or where you frequently travel, prohibiting carrying a rifle on you concealed in a bag or pack. Another concern is simply the physical size and weight of a long gun for daily carry. If the piece is too large and heavy, it will surely be left behind as too burdensome after a time or two. It does you zero good if it’s been left back in your vehicle or home when you need it. Another issue is physically concealing a rifle. Do you REALLY think you are fooling anyone with that tennis racket case slung on your back? If you have to break down your AR to transport it, how much time will it take you, under stress, to reassemble it and get it into action?

SIG Sauer Copperhead Pistol
SIG Sauer’s Copperhead pistol can be inconspicuously carried in a relatively small bag, satchel or sling bag as seen here, until needed.

The ideal piece is compact enough to store easily in a small bag which will not look out of place as you go about your day. At least as important as size, in my book anyways, is weight. The piece with associated optic, white light and loaded magazines needs to be light enough it will not become an undesired burden as you go about your day. Ideally it will be quick into action allowing you to draw it and immediately engage a threat. If it has a stock or stabilizing brace it should be designed to allow rapid deployment. Ideally it will be equipped with an optic and white light enabling effective use in low/no light scenarios. Plus, due to the growing use of body armor by active shooters I would recommend having the capability of penetrating Level IIIA soft body armor. It should also be accurate enough to be head-shot capable at 100 yards.

Now, with all that out of the way, let’s take a look at SIG Sauer’s Copperhead pistol. I had my first opportunity to handle and fire this interesting piece in August and then again in December of 2018 while filming segments for TV at SIG Arms Academy in New Hampshire. I’m a fan of the Copperhead’s big brother, the Rattler in 300 AAC Blackout, and so was curious to see what SIG Sauer had developed to complement it.

SIG Sauer Copperhead Pistol
SIG Sauer’s Copperhead is a smaller pistol caliber sibling to their 300 BLK Rattler and is based on their popular MPX platform.

The Copperhead is built on SIG Sauer’s popular MPX platform and manufactured in Newington, New Hampshire. Unlike an MP5K, Skorpian or Kedr the Copperhead is gas operated with a short-stroke piston operating system. This in and of itself sets the Copperhead apart from the pistol-caliber blow-back and delayed blow-back crowd. Caliber is the world standard, 9x19mm Parabellum. Barrel length is a very short 3.5 inches. This is just .4 inch longer than SIG Sauer’s micro compact P365 pistol. In comparison, barrel length on my Zenith MP5K PDW clone is 6 inches. Should the short barrel be a concern? You will see a reduction in velocity, how much of a loss will depend upon the load. At the end of the muzzle you will find a much abbreviated flash suppressor.

SIG Sauer Copperhead Pistol
The Copperhead features an ambidextrous safety and bolt release making it very easy to run with either hand.

Controls are similar to an AR-15, well placed and easy to manipulate. There are a couple upgrades though. An ambidextrous safety is fitted with a full-length lever on the left side and a shortened lever on the right. Ambidextrous magazine releases are fitted and the charging handle is ambidextrous. Lastly there is a bolt release lever on the right side of the receiver. This only serves to release the bolt; you cannot lock the bolt back with this lever. The single-stage trigger pull is heavy, but useable.

SIG Sauer Copperhead Pistol
The Copperhead’s controls are similar to an AR-15, making for an easy transition for anyone used to running an AR.

The profile of the Copperhead is as blocky as a 1985 Oldsmobile 442 sedan. Running along the top of the beefy rectangular upper receiver is a MIL STD 1913 rail. This makes mounting optics, iron sights and accessories very easy. The lower receiver sports an over-size flared magazine well, enlarged triggerguard and a distinctive looking pistolgrip. The pistolgrip is designed to reduce its size while still providing you a grip you can get all your fingers on. At the rear of the receiver is a MIL STD 1913 rail.

SIG Sauer Copperhead Pistol
The Copperhead comes fitted with a robust collapsing stabilizing brace seen here fully closed.

Riding on two struts is a stabilizing pistol brace. This can be split open, your arm inserted and Velcro tightened, securing it to your forearm to aid accuracy. The polymer brace can be rotated 360 degrees to ensure an optimum fit. To extend the brace you simply pull straight back until it locks into place. To close, depress the release button on the right rear of the receiver and slide it in. Overall length with the brace collapsed is 14 inches and 18.75 inches with it extended. Distance from the end of the muzzle device to the MIL STD 1913 rail at the rear of the receiver is just over 12 inches. Distance from the end of the brace to the trigger is 11 inches. The pistol with no magazine weighs 4.5 pounds and my review sample with a SIG Sauer Romeo 3 red dot sight and full 20-round magazine weighs 5.5 pounds.

SIG Sauer Copperhead Pistol
A SIG Sauer Romeo 3 red dot sight was mounted for testing and it performed well with no problems.

The Copperhead utilizes the MPX’s short-stroke gas piston operating system, in an abbreviated fashion. The design utilizes a rear take-down pin and front pivot pin just like an AR. So take-down is very simple. The bolt carrier and recoil spring assembly removes as one unit, with the recoil springs on top. The whole assembly weighs 11.7 ounces and with the recoil spring assembly removed the bolt carrier weighs 6.65 ounces. In the hand the bolt carrier assembly looks familiar enough for anyone familiar with an AR to figure out. While the carrier is shorter than an AR’s, and features dual captured recoil springs on top, the general layout is the same.

Simply tilting the front of the recoil spring assembly up will allow it to be slid side-ways to the left and off the bolt carrier assembly. With this removed the bolt carrier is only 3.5 inches in length. To take this down, remove the firing pin retainer by pulling it out on the right side of the bolt carrier. With this slid out of the way the spring loaded firing pin can be removed straight to the rear. The cam pin can now be removed, just like an AR, and the bolt can then be pulled from the front of the carrier.


SIG Sauer Copperhead Pistol
Barrel length is just 3.5 inches and it is fitted with a very short flash suppressor.

Of interest is the Copperhead’s bolt. This features a slot for the fixed receiver mounted ejector and a spring-loaded extractor. Unlike a standard AR, the Copperhead’s rotating bolt features rounded lugs to prevent fractures and increase durability. Actually the whole system has been designed to provide a very long service life before any parts need to be replaced. The piece feels very over-built for a 9mm Parabellum. While the Copperhead is lighter than my Zenith MP5K PDW clone, it is also longer. This is due to the collapsing brace jutting from the rear of the receiver compared to the side-folding stock on the MP5K PDW. A side-folding brace would chop a bit of length off the Copperhead making it even more compact for discreet carry.

SIG Sauer Copperhead Pistol
Simply yank on the stabilizing brace to extend it and lock it securely into place.

While reviewing the SIG Sauer’s Copperhead pistol I carried it in two small bags. One was from Vertx and the other was an inexpensive canvas sling bag from Amazon. The Vertx bag looks cool and was specifically designed with input from “operators” to optimize its function operationally, including an over-size handle on one zipper for quick access to your firearm. This brings us to another very important point to consider, carry bag selection.

While the Vertx bag is very well made, has a host of features and is designed to carry a firearm I would not recommend it. Why? Simply due to the fact it is a bag designed and marketed to carry a firearm from a company which sells discreet carry bags. In plain language it is what it is and sticks out like a sore thumb, especially with that big “quick access” zipper handle. While it will impress your tactical bros, it’s a bit high visibility for my personal tastes. I recommend buying a bag manufactured by a company with zero links to the firearms industry or anything “tactical”. Look for something simple, resembling what other people in your locale actually carry. I bought my favorite sling bag for $1 at a Goodwill store. Another point to consider is having a bag with multiple separated compartments. This allows you to carry and access common items you may wish to carry without having to open, and expose, the section the firearm is stored in.

SIG Sauer Copperhead Pistol
The Copperhead is small, maneuverable, easy to hit with and easy to control.

I began testing by checking Point of Impact at 50 yards and then started shooting groups from the bench. Four 5-shot groups were fired from a rest at 50 yards using four different loads. These consisted of Black Hills Ammunition’s 124-grain +P JHP, SIG Sauer’s 365 V-Crown 115-grain JHP and 365 115-grain FMJ along with TulAmmo’s economical 115-grain FMJ supplied by USARM NORD LLC. Loading up a 20-round magazine I settled in and got to work. The charging handle was a bit stiff to run with that “new gun” feel. Rounds fed smoothly and chambered without any issues. The safety operated smoothly while the trigger had a bit of creep while being on the heavy side. Recoil was very mild and the Copperhead extracted and ejected like a champ.

Best accuracy was obtained using Black Hills Ammunition’s 124-grain JHP +P load. This averaged 1.7 inches at 1,114 fps. This load would consistently put 4 out of 5 rounds into about 1 inch. SIG Sauer’s 365 V-Crown 115-grain JHP averaged 2.5 inches at 1,082 fps while TulAmmo’s 115-grain FMJ averaged 3.1 inches at 1,098 fps. The Copperhead didn’t appear to like SIG Sauer’s 365 115-grain FMJ load which averaged 6 inches at 1,055 fps. Report was mild and the Copperhead was very comfortable to fire from the bench.

SIG Sauer Copperhead Pistol
Best accuracy was obtained using Black Hills Ammunition’s 124-grain JHP +P load which posted this nice, but a bit low, 4-inch group at 100 yards on a silhouette.

After gathering up my paper targets I extended the distance to 100 yards. Here I used a plain white steel reduced size silhouette as my target. All four loads would easily stay on the target at this distance. Firing from the bench the Black Hills Ammunition 124-grain JHP +P load posted a best of 5 shots into 4 inches and averaged 4.7 inches. SIG Sauer’s 365 V-Crown 115-grain JHP posted a best of 5 shots into 5.3 inches and averaged 5.7 inches. Next I tried engaging 8-inch plates at 100 yards. These are head size, and the Copperhead made consistent hits using the Black Hills and the SIG Sauer 365 V-Crown JHP.

Running SIG Sauer’s Copperhead through a variety of drills showed it to be easy to operate and quick into action. Anyone who is familiar with running an AR-15 will have no trouble operating a Copperhead. The stabilizing brace is easy to deploy and locks securely into place. The controls are well laid out and easy to manipulate. Unlike an MP5K PDW, the bolt locks back on the last shot and magazines eject with the push of a button. While small, it is very easy to make rapid hits with using the brace.

SIG Sauer Copperhead Pistol
Controls are similar to an AR-15, well placed and easy to manipulate. Note the ambidextrous magazine release.

While practicing deploying it from a bag I also did some single and two-handed shooting without extending the brace. The Copperhead was easy to shoot this way, and sort of felt like an over-sized Mauser C.96. Moving rapidly behind cover I’d then snap the brace out and re-engage the targets. I experienced zero issues of any kind during testing. The Copperhead fed, fired, extracted and ejected every round without issue, even the economical Russian steel case ammunition. When I finished up on the range I found the Copperhead to be very easy to take-down and clean.

SIG Sauer Copperhead Pistol
A look at the Copperhead broken down for routine maintenance. It strips easily without tools.

After spending a bit of time with it I do have my thoughts on SIG Sauer’s Copperhead pistol. It can be carried discreetly in a relatively small bag, something smaller than a common laptop messenger bag. It is quick to deploy, easy to control and is capable of making headshots at 100 yards. Reliability during testing was excellent. The very short 3.5 inch barrel degrades standard velocity 9mm Parabellum ammunition down into the 9mm Makarov range. While it is possible to penetrate Level IIIA soft body armor using commercial off the shelf 9mm Parabellum ammunition, the Copperhead will only do it at relatively close distances due to the low velocity.

While the collapsing stabilizing brace is very quick to deploy and locks solidly into place, I feel it adds unnecessary length to the gun. By switching to a side-folding brace the overall length could be shortened by approximately 1.75 inches. While this doesn’t sound like much, it is. One of the goals of such a piece is to be able to carry it in a bag so small no one would expect it to contain a brace equipped PDW style pistol. Switching to a side-folding brace would also remove weight from the gun by getting rid of those two metal struts. For a gun that is going to be carried a lot and shot seldom, lighter is better.

SIG Sauer Copperhead Pistol
Notes: Accuracy results are averages of four five-shot groups fired from a rest at 50 and 100 yards. Velocity figures are 10-shot averages recorded with a LabRadar Doppler chronograph at an ambient temperature of 94 degrees F at 1,030 feet above Sea Level.

There is a lot to like about the SIG Sauer Copperhead, if you have a need for a firearm which fills this particular niche. A pistol with a stabilizing brace which measures just 14 inches (and could measure 12.2 inches) overall is not common. For example a CCA Micro Roni chassis for a Glock pistol measures 15 inches and is quite a bit bulkier. If you’re a considering a piece to fill the role of a PDW for bag carry to complement your CCW pistol the Copperhead’s MSRP is $1835.


SIG Sauer

Black Hills Ammunition



SIG Sauer MPX Copperhead Pistol Specs

  • Action: Short-stroke gas with rotating bolt
  • Caliber: 9x19mm Parabellum
  • Barrel: 3.5 inches cold hammer forged
  • Rifling: 1-10 inch twist
  • Overall length: 14 inches collapsed, 18.75 inches extended
  • Trigger: Single-Stage with 7 pound pull
  • Feed: 20-round detachable box magazine
  • Weight: 4.5 pounds w/out mag or optic
  • Finish: Cerakote E190
  • MSRP: $1,835
  • Manufacturer: SIG Sauer, (603) 610-3000,

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