Here’s an in-depth look at the Beretta Cx4 Storm.
By Joe Grine via The Truth About Guns
Beretta released the “Cx4 Storm” in 2003, hoping to compete in the law enforcement market. The case for the Cx4 is strong, since it’s a lightweight, accurate, reliable blowback-operated carbine that allows an officer to use the same magazine as his or her 92 FS or Px4 pistol.
Unfortunately for Beretta, most departments have opted for AR-15s and M-4s, so the Cx4 never really achieved the type of US LEO market acceptance that I imagine Beretta would have hoped. But that doesn’t mean the venerable Cx4 isn’t a viable option.
The Beretta Cx4 Storm is a blowback-operated polymer-framed carbine that fires from the closed bolt. The simple blow-back action ensures perfect reliability. It weighs in at a very light 5.75 lbs and has an overall length of 29.5 inches. Available chamberings include 9x19mm and .40 S&W; Beretta recently discontinued production of the .45 ACP version.
The Cx4 is fed via pistol magazines that are inserted Uzi-style (i.e. through the pistol grip). The advantage to this system is that it is easy to insert magazines even in complete darkness, because the trigger hand gives you a point of reference for the location of the mag-well.
The Cx4 sports a 16-inch, 6-groove, RH twist barrel which is both hammer-forged and chrome lined.
The Cx4 isn’t fully ambidextrous, but most of the controls are reversible. From the factory, the Cx4 is set up for right-handed operation, including right handed ejection. In about five minutes (or less with practice), the operator can reverse the extractor and ejector, the safety (1), the magazine release (2), the cocking handle (3), and the ejection port cover (4) for left handed use. The only control that is not reversible is the bolt release lever.
The fixed thumbhole stock can be adjusted in length via the use of up to three 15mm (.6 inch) spacers. In my opinion, pretty much every thumbhole stock sucks on a tactical rifle. However, the Beretta Cx4 is not nearly as bad as others I have tried. In fact, it is about as good as one might expect, given the political limitations Beretta was faced with.
Ergonomics and Operator Controls
The biggest selling point for the Cx4 has got to be its lightweight, comfortable design. It feels as comfortable as a broken-in set of Ferragamo Derbys. I’ve fired scores of different pistol caliber carbines and SMGs, and perhaps none feel as good in the hand as the Beretta Cx4. Even the legendary HK MP5 feels big and clunky in comparison, and an UZI feels like a boat anchor next to the Cx4.
One of the most important design criteria of the Cx4 was the use of pistol-like controls. Beretta intended to ensure that police officers using their pistols such as the 92F or Px4 Storm could make easy transitions to the Cx4. In this regard, Beretta’s engineers designed the magazine release and bolt release to be in familiar locations for pistol shooters.
The Cx4 is festooned with safety features. A manual safety blocks the trigger, and can be engaged regardless of whether the bolt is open or closed. The carbine also features a bolt travel stop safety, a firing pin block safety, a hammer block / drop safety. Should the carbine be dropped or struck against an object, the bolt travel stop safety will not allow the bolt to cycle.
As an additional safety feature, Beretta added a loaded chamber indicator on the ejector.
The plastic factory trigger is a definite low point, and is primarily what made me initially have reservations about the Cx4. For some reason, Beretta still has an old-school mindset when it comes to triggers on tactical rifles and carbines. In short, Beretta likes them heavy.
As a former Army officer, I get the fact that heavier triggers equate — at least in theory — to fewer negligent discharges. But the US civilian market definitely places high value on 3-5 pound triggers. So Beretta choosing to put heavy triggers on their tactical rifles frustrates me to no end, since I know that Beretta don’t do that with their shotguns. My Beretta Silver Pigeon III shotgun’s trigger breaks at around 5 lbs. As it should.
Unlike the Silver Pigeon, the factory Cx4 trigger pull is long and creepier than Joe Biden. To make matters worse, the overall trigger weight is in the bowling ball range — about 10-12 pounds range. That’s entirely unacceptable. While it’s possible to master a heavy trigger with practice, I found myself frequently pulling the lightweight carbine off target a bit as I attempted to “squeeze” the trigger. Needless the say, it was fairly obvious to me that the trigger is the “limiting factor” when it comes to accuracy. As mentioned above, I eventually replaced it with the excellent Sierra Papa mods.
I have one other interesting and little-known fact about the Cx4 trigger. The trigger assembly contains a small ball bearing that rolls back in forth in a cradle. When the carbine is pointed up or down above a certain angle, the ball bearing moves in a manner that causes the trigger pull to increase by a few pounds. I don’t know exactly how it works, but I do know that it is possible to remove that little ball bearing for a smoother trigger. I have shot well over 3000 rounds without the ball bearing with no effect on accuracy or reliability.
The Cx4’s iron sights are unique and it took me a while to get to appreciate them. The front post sight is adjustable for both windage and elevation, but it does require the use of a proprietary tool (included). The rear sight is a simple “L-shaped” sight, similar to World War II issue M-1 carbines or Enfield No.4 mk 1s.
I learned how to shoot using sights on my Ruger 10/22, but I was never really a great shot with those Ruger sights. However, I really started to master irons at age 14 when I shot M-16A1s at my first JROTC summer camp. The instructors taught us to use the protective “ears” on U.S. military front sights as an aiming “aid” by lining them up with the circle created by the rear aperture, as shown in the photo below. I actually try to back off the rear sight far enough so that the ears “touch” the circle, but not everybody uses that technique. In any event, these outwardly curved “ears” have been a standard on every U.S. military rifle since the Model of 1917.
But the U.S. military design is not the only one that uses the protective shield of the front post sight as part of the aiming system. For example, the famous HK front sights are either curved inward or create a complete circle, and can be used to make a very intuitive a “circle in a circle” sight picture.
The Beretta Cx4 does have protective ears, but it is less intuitive as to how you can use them as aiming aide because they don’t turn outward like the U.S. military, nor do they make an obvious circle like the HK front sights. However, if you only focus on the outer edge of the Cx4 front sight ears, it does make a circle pattern, and you can use those outside edges to mirror the “circle” pattern created by the rear peep sight. It works, but it is not as obvious or intuitive as the HK sights.
But let’s not kid ourselves… that beautiful aluminum picatinny is just screaming for optics, and I don’t see too many guys running the Cx4 with irons in any event. Slap an Aimpoint T-1 on that puppy and you won’t need to worry too much about iron sights!
One really nice feature is that both the front and rear sights can be pushed down out of the way when using optics, as shown in the photos above.
Beretta makes two versions of the Cx4. One version uses magazines that are compatible with the Px4. The other is compatible with “90 series” of pistols (92F/96 etc) mags. If you have the version made for the Px4 mags, 8000 series magazines (using optional adapters),you can use P92/96 and 8000 series magazines by purchasing two separate magazine inserts. In either case, the magazines are made by Mec-gar, and are extremely high quality.
The one thing that I found a bit odd is that the 20 and 30 round magazines come from the factory with extremely heavy springs. The first time I loaded them it was extremely difficult to get them loaded to full capacity, even using the factory magazine loader accessory. Thankfully, the magazine springs lightened up over time, and now it is possible to load them to capacity even without the loader.
The Beretta Cx4 is relatively simple to disassemble. A single metal-reinforced polymer non-captured “disassembly latch” holds the upper and lower receivers together. It can be removed by pushing it out from either end. Next, the bolt assembly can be removed by backing it out of the upper until you reach an index point, where the charging handle is removed. Once the charging handle is removed, the bolt carrier can be removed out of the rear of the upper receiver.
The extractor, ejector and spring guide assembly are held in the bolt assembly via a “retaining spring,” which is a “horseshoe” shaped leaf spring. Once you remove that spring, everything pretty much falls out. Pay attention to the way the extractor and ejector are positioned, because the direction of ejection is reversible depending on which side of the bolt carrier you install the extractor and ejector. The design is both simple and ingenious.
The trigger housing can be removed from the lower receiver. Rather than explain how to do it, I will simply direct you here for a step-by step video.
Accuracy & Reliability
One definite high point for the Cx4 is its utter reliability. Since I purchased the Beretta, I have fired roughly 5000 +/- rounds through the weapon without a single malfunction of any kind. I typically don’t run the cheapest ammo out there, but I’m not running the expensive stuff either. Mostly, I run a combination of gun show reloads, UMC, Winchester (mostly Wally World white box), Tula Brass, Blazer Brass, and American Eagle. Again, the Cx4 eats it all up with boring regularity. Just how I like it.
Accuracy on the Beretta was a bit disappointing at first, with groups averaging roughly 2-3 inches at 50 yards. As mentioned above, the trigger group clearly is the limiting factor to achieving peak accuracy. I probably could have spent a bunch of time and money “learning” the trigger’s quirks, but I went the aftermarket route. Indeed, accuracy improved once I installed the Sierra Papa modifications. Shown above is a particularly nice 50 yard group and some “typical” 100 yard groups which I achieved with the Sierra Papa upgrades and a 6x scope (not shown). Make no mistake, even as modified, it’s still not a target trigger. But it’s a lot better than it was. More on that below.
Beretta typically is fairly generous with its accessory package, and the Cx4 does not disappoint in this regard. It includes an excellent polymer hard case, two 15-round magazines, a magazine loader, a sight adjustment tool, a cleaning kit (rod, bore mop, bronze brush, and jag), gun lock, and one two-inch section of rail which can be mounted on either side of the firearm.
Note: If you buy a new Cx4, pay close attention to the warranty card. The Cx4 comes with a “1(+2)” warranty. What that means is that it comes with a one year warranty, but if you send in the warranty card within 30 days of purchase, Beretta will extend the warranty for two additional years.
Sierra Papa “Upgrade” Parts
As discussed above, the OEM version of the Cx4 Storm is an excellent design but has a few annoying quirks/flaws. If you want to improve your CX4 to make it go from “good” to “great,” you owe it to yourself to check out Sierra Papa. As they state on their website, their goal is to “improve the breed.”
The owner, Brian Montgomery, is a retired airline pilot who became a Cx4 enthusiast soon after the carbine was released. With an extensive engineering and manufacturing background, he began figuring out ways to improve the weak links in the system. The photo below shows both the Sierra Papa parts and the tools needed to install them. SP used to allow the purchaser to install the parts, but their current policy is to require you to send your trigger pack to them so that they can inspect the unit and decide whether a sear clip is needed. Click here to learn more for the reasoning behind this new policy.
Sierra Papa completes the work very quickly, ensuring a typical 7-10 day door-to-door turn-around time, including shipping.
In the photo below, you can see the difference between the OEM plastic hammer and the SP Stainless steel hammer. In the event the photo does not speak for itself, trust me when I tell you that the SP is a gorgeously milled part that vastly improves the trigger pull. The factory OEM part is very light, and only generates enough inertia when driven by a powerful hammer spring to ensure sufficient energy to reliably operate the firing pin. Unfortunately, the “heavy” hammer spring, in turn, requires a heavy trigger pull. Thus, when you switch to the heavier Sierra Papa hammer, you can also use a lighter hammer spring, which can be operated by a lighter trigger.
Out of the box, the Beretta Cx4 is diamond in the rough. It shows great potential because it’s utterly reliable, light, and compact. However, the plastic hammer makes for a heavy, creepy trigger pull that robs the carbine of its inherent accuracy. The government-mandated thumbhole stock is well-designed, but still detracts from the otherwise good handling characteristics. Fortunately, Sierra Papa can fix these faults, and turning the Cx4 Storm into a real Ferrari. Admittedly, like a Ferrari, these aftermarket mod turn the Cx4 into an expensive project, so you have to decide if it is worth the cost. By the time you invest in a number of 30-round mags, rails, optics, and the Sierra Papa upgrades, you can easily have $1500-2000 into the project. I can easily justify the initial investment by recognizing that the 9×19 chambering will pay for itself in ammo saving: even if you shoot a relatively conservative 2000-3000 rounds a year, the cost savings add up quickly. However, $2k is a big number, and I realize that for many folks it is simply out of the question.
In thinking about pistol caliber carbines, there are lots of options. At the top of the market you have HK SP-89s, HK-94s, and HK UMPs. Colt and JP make 9mm ARs that are really nice, but again they tend to be rather expensive. Sig-Sauer just released the excellent MPX ($1600-ish), and I am definitely going to buy one in the near future. The CZ scorpion Evo 3 is also on the market and comes in at a highly competitive price. At the lower end of the price scale, Kel-Tec’s Sub 2000 is a nice gun of you can ever find them, and the Hi-Point 995 is ugly but apparently works pretty well. The Taurus CT-9 would have been serious competition for the Beretta if Taurus had addressed the 10-round magazine problem, and figured out a way to make the CT-9 a bit more compact. But instead Taurus has discontinued importation of the CT-9, so it’s DOA.
Despite the other options, I think the Beretta offers a professional, bet-your-life-on-it patrol carbine for a very competitive price. Once I solved the trigger “issue,” I really started to like… er.. love… this carbine, and I can recommend it without any reservations. Indeed, it makes a fine addition to my Beretta collection. Better yet, all of my friends who have shot this gun walk away saying “I gotta get me one of those.” That is high praise and it is well deserved.
Importer: Beretta USA; (301) 283-2191;
Calibers: 9×19 (as tested), .40 S&W; (.45 ACP Discontinued).
Action Type: blowback-operated semi-auto
Frame: molded techno-polymer upper and lower.
Barrel: hammer forged, chrome lined, 16.25inch, six-groove, RH twist
Magazine Capacity (9×19): (10, 15, 18, 20, 30)
Sights: aperture rear, post front adjustable for windage and elevation
Trigger: single-stage 10+ lbs.
Overall Length: 29.7”
Weight: 5 lbs., 12 ozs.
Supplied Accessories: hard case, manual, short rail section, spare magazine, magazine loader.
Street Price: $600 -$800
Ratings (Out of Five Stars):
Accuracy (Stock): * * *
The barrel is inherently accurate, but the 10+ lb. trigger robs the gun of its accuracy potential.
Accuracy (with Sierra Papa Modifications) * * * * *
Ah, much better.
Ergonomics & Aesthetics: * * * * *
A true Ferrari.
Reliability * * * * *
Eats anything, never jams.
Customization: * * * *
It’s not an AR platform, but the basics are covered. Point taken away due to no aftermarket folding stocks. Bonus point for using Beretta 30-round mags.
Overall: * * * *
Once you get the Sierra Papa mods, there are few 9mm carbines that are superior to the Cx4, and those that are cost 2x more than the Beretta.