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Rotary Action Autopistols—What Are They, and Why Do You Need One?

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The Glock 19 (top) uses a tilting barrel short recoil system while the Beretta PX4 Storm (bottom) uses a rotary locking system.

The Glock 19 (top) uses a tilting barrel short recoil system while the Beretta PX4 Storm (bottom) uses a rotary locking system.

To learn more about the Beretta PX4 Storm, click this link: http://www.px4storm.com/.

To purchase a Beretta PX4 Storm on GunsAmerica.com, click this link: https://www.gunsamerica.com/Search.aspx?T=PX4.

What is a rotary action pistol, you may ask? And do I need one? Well, just to make sure we are all on the same page, let’s consider what they are. In the world of rifles, where a bolt locks into a barrel or barrel extension, a “rotational” locking mechanism is a common thing. Lugs on the bolt move past other lugs in the chamber, and when rotated, the bolt is firmly locked into the chamber because the lugs can’t move past each other. To separate the two, something has to rotate the bolt to unlock the lugs. Depending on the design, either manual operation or gas pressure unlocks the bolt.

Pistols are a bit different. While a rifle barrel and chamber are (generally) stationary, and just the bolt moves backward to extract a case and load a new cartridge, a pistol barrel (generally) recoils backward a bit along with the “bolt.” Of course in a pistol, it’s not really a called a bolt, but a slide that has a breech face machined into it, so it serves a similar purpose. You might think of a semi-automatic pistol slide kind of like a combination bolt and bolt carrier.

A semi-automatic pistol operates because of a carefully choreographed balance of time and motion. The barrel and slide lock together to create a sealed chamber. After the shot is fired, this chamber stays closed until the conflagration inside chills out a bit, and pressure falls to manageable levels. If the slide and barrel separated at the instant of ignition, you would have all the chaos of a muzzle blast except it would be right around your face and hands, coming out the back of the barrel instead of the muzzle. So, the slide and barrel need to be locked together as the cartridge ignites to keep the chamber sealed. As pressure drops, they can separate so the process of extraction and loading can begin.

Many semi-automatic pistols, like this Glock 19, lock via fit between the barrel and the ejection port.

Many semi-automatic pistols, like this Glock 19, lock via fit between a square portion of the barrel hood and the ejection port.

The solution that makes a semi-automatic pistol work is a delayed action, where the slide and barrel remain locked together for a fraction of a second. After that, the slide and barrel can unlock and separate safely. Just as with our rifle example at the beginning of this article, the pistol barrel and slide lock together with lugs machined into the barrel and slide. Depending on the “design” of the unlocking mechanism, the barrel may either unlock from the slide by tilting out of alignment, or, in the case we’re going to talk about today, by rotating like a rifle bolt.

The ramped lug on this Glock 19 barrel tilts the barrel down, unlocking it from the slide.

The ramped lug on this Glock 19 barrel tilts the barrel down, unlocking it from the slide.

Pistols like Glocks, Springfield Armory XD family members, and Smith & Wesson MP pistols use a short-recoil tilting barrel system to make this work. The energy of the cartridge drives the slide and barrel backward. These two parts are temporarily locked together as the squared back of the barrel locks into the top of the ejection port. A lug extension on the bottom of the barrel eventually catches a locking block in the frame, causing the barrel to tilt downward, thereby unlocking it from the slide. The barrel stops moving backward while the side continues rearward to complete the ejection, cocking, and reloading actions.

The groove in the Beretta PX4 barrel causes rotation of the barrel during recoil.

The groove in the Beretta PX4 barrel (bottom) causes rotation of the barrel during recoil.

How rotary action works

Rotary action pistols are somewhat rare when compared against more traditional tilting barrel designs. One of the more common and popular of these relatively rare birds is the Beretta PX4 Storm. With a rotary-action pistol, the results are similar, but the method differs. The barrel and slide still remain locked together for a hot second until pressure drops. However, as the slide travels back, the barrel rotates, rather than tilts, to unlock from the slide.

Using the Beretta PX4 Storm as an example, there are several design features that cause the barrel rotation and subsequent unlock from the slide.

First, the barrel locks to the slide in two different places. The front edge of the ejection port and a ledge machined into the inside of the slide both serve to prevent the barrel from moving relative to the slide when the barrel is oriented in the normal firing position. Hold that thought for just a minute…

 

Here you can see how the central block engages the barrel groove.

Here you can see how the central block (below) engages the barrel groove (above).

The captive recoil spring is anchored by a central block positioned under the chamber. This block has a lug that mates with a groove cut into the bottom of the barrel, just under the chamber. The groove is angled so that when the barrel travels over the central block lug, which remains anchored by the frame, the lug causes the barrel to rotate about one-eighth of a turn in place. As the barrel rotates, those two locking points move out of alignment and the barrel releases from the slide. So, like the bolt on an AR or bolt-action rifle, the rotation drives the lugs out of the locked position.

You can see where the barrel locks to the front right edge of the ejection port. There's a second locking point on an internal ledge in the slide.

You can see where the barrel locks to the front right edge of the ejection port. There’s a second locking point on an internal ledge in the slide.

The really nifty thing about the design is that it’s not reliant on just that central block lug forcing the barrel to turn as it moves backward. The rifling pattern is cut with a right-hand twist, so as the bullet travels down the barrel, it tends to torque the barrel clockwise from the shooter’s perspective. That clockwise rotation is not coincidentally the same direction of turn required to unlock the barrel from the slide.

Why rotary action?

There are a few theoretical advantages to a rotary action over other designs.

With a tilt-lock system, the barrel physically goes out of alignment with both the sights and the target during the recoil process. Accuracy from shot to shot depends entirely on the barrel moving back into the exact same position relative to the slide and sights as before the recoil action. With a rotary system, the barrel still moves, but it never comes out of alignment with the slide and sights because it rotates in place. In theory, with less moving around, a rotary system may have mechanical accuracy advantage. In reality, it’s probably a moot point. Unless we go out and build pistols of different action types, bolt them to a granite block, then start a bench rest pistol competition at 100 yards, the whole accuracy difference will never be visible in practical applications. There are plenty of pistols with tilting-barrel, link, and rotary actions that are already far more accurate than anyone of us can shoot.

Note how the barrel remains perfectly straight during recoil. That's one of the benefits of the rotary system.

Note how the barrel remains perfectly straight during the rearward movement of the slide. That’s one of the benefits of the rotary system.

The other theoretical advantage is an improved felt recoil experience. Rather than a direct backward action as with a tilting barrel system, the rotary movement bleeds off some energy as the barrel rotates, so, again, in theory, felt recoil is reduced. However, it can result in a sensation of “torquing” of the pistol in the hand.

Here you can see how the muzzle rises during recoil on a tilting barrel design.

Here you can see how the muzzle rises during the rearward movement of the slide on a tilting barrel design.

Last, the design lends itself to a lower bore axis relative to the hand. The straight back and forth movement of the barrel allows the top cartridge in the magazine stack to be oriented almost directly behind the chamber. There’s no wasted space between the magazine and the barrel, so in effect, the barrel is lower relative to the frame. You’ll notice that there is hardly any feed ramp on a rotary action pistol because it’s simply not required. Not only does the straight in feed help with reliability, but it also allows for a fully supported chamber. Of course, the lower the barrel is relative to your hand, the less muzzle flip you’ll experience.

And finally, theoretically, it can allow for a lower bore axis than a traditional tilting barrel design, which requires more room below for the dipping movement of the barrel during recoil.

So that’s what rotary action is all about. Is one right for you? I recommend trying one out for yourself to decide. Give it a spin!

To learn more about the Beretta PX4 Storm, click this link: http://www.px4storm.com/.

To purchase a Beretta PX4 Storm on GunsAmerica.com, click this link: https://www.gunsamerica.com/Search.aspx?T=PX4.

{ 26 comments… add one }
  • Johnny Red November 15, 2016, 6:37 pm

    I’m intrigued. Can someone name other rotary action pistols?

    • Graham Baates November 16, 2016, 12:55 pm

      Grand Power makes excellent rotary pistols. Here’s a review of one I have https://www.youtube.com/watch?v=Dk41ClwO-m4&t=9s

    • Darvell November 18, 2016, 9:14 pm

      In addition to the PX4 line from Beretta, all of the Beretta Cougar models also have the rotary locking barrel. I have two each of .40S&W (Cougar 8040) and .45ACP (8045) and I’m surprise how light the felt recoil seems. There’s also the 9mm (Cougar 8000), but I don’t have one of those, so I can’t report on it. (The Stoeger Cougar is currently in production and replaced the Beretta Cougar line.)

  • Larry November 15, 2016, 4:23 pm

    I was out shooting with friends just yesterday. I put about 100 rounds thru my Beretta Storm sub compact 40 caliber. It was the most accurate gun out of seven that we shot. It comes in 9mm also & I would recommend it to all.

  • ALOOFinc November 15, 2016, 2:23 pm

    The misbegotten Colt Model 2000 (See website below as I am sure nobody else remembers it.) used a rotating barrel and had no promise of accuracy at all. The Steyr- Hahn was an early, (1911-1912) successful military auto which served until the end of WWII.
    https://www.forgottenweapons.com/colt-all-american-2000-video/
    https://en.wikipedia.org/wiki/Steyr_M1912

  • tweedmus November 15, 2016, 6:47 am

    This design goes back to the 1905 Savage 45 which gave the Colt 1905 a good run for the money when the Army was doing trials for the first auto pistol. The Colt won, but because of the Savage’s competition, we have the classic 1911. I’ve collected Savage auto pistols for years but have never been able to afford a 1905 the few times I’ve encountered one. The pocket pistols are very accurate, sit low in the hand and point well but do have a very stiff trigger pull, which can be managed by an experienced shooter.

  • Kivaari November 14, 2016, 8:49 pm

    If the PX4 reduces recoil, I don’t notice it. The first time I shot mine I swore it recoiled more than a .45 auto. I was certainly surprised at the recoil.

  • Franke November 14, 2016, 5:14 pm

    My STI GP-6 has a rotary barrel system and I consistently shoot it better than my XDm 5.25 or my M&P 9L Pro. Didn’t know about the PX4. Thanks–

  • mach37 November 14, 2016, 3:43 pm

    While the barrel rotates, wouldn’t it be just as accurate to call this a cam-action pistol? Considering the family resemblance of “revolver” and “rotary action,” having never heard of this action before, I was expecting something more revolver-like.

    • DaveGinOly November 14, 2016, 8:08 pm

      Even an AR uses a cam to make the bolt rotate. Nobody would call that a “cam action” firearm, it’s just a rotating bolt (instead of a rotating barrel).

  • Dale Bailey November 14, 2016, 12:48 pm

    The pistol that ended up second to the model 1911 in the military trials was a Savage with a rotary action . My father had one of the commercial Savage pistols in .32 auto. ,it was extremely accurate despite rather miniscule sights .

  • december November 14, 2016, 9:33 am

    I use a Grand Power Xcaliber for competition. With carpel tunnel in both wrists it is much easier on my wrists.
    Really nicely finished pistol as well, even my gunsmith who has been taking apart more firearms then I will ever see was pretty impressed with the fit and finish inside and out.

    Sure the Glocks are used by most but it is because of sponsorship and many who are not following the heard.

  • Dave November 14, 2016, 8:48 am

    Been around guns all my life, but fairly new to handguns (10 to 15 years). This was really a great article for me and I just wanted to say thank you!

    • Tortoise November 14, 2016, 4:37 pm

      Right on Dave. I’ve been playing around with guns forever and never in the least understood this. More than once I’ve looked at my pistols when locked back and wondered why the barrel was tilted out of the axis of the gun……. a big thanks to the author… it now makes sense….

  • Todd Jaffe November 14, 2016, 7:53 am

    I have a Beretta PX4 in 45, the special forces version that has an extended barrel for suppression. If you use a Pederson device with a locking suppressor or even a threaded suppressor they will work.

  • Bill November 14, 2016, 5:42 am

    Stoeger is a division of Beretta, and is manufacturing the Beretta designed and originally manufactured, rotary barrel, Model 8000 Cougar in an ISO facility in Turkey. Just as good as the Storm, for less money, just not quite as snazzy looking. I have one and love it.

  • Rich K. November 14, 2016, 5:01 am

    The Mexican Obregon pistol, which resembled a 1911 with an odd-looking slide, used a rotary action way back in the 1930’s https://en.wikipedia.org/wiki/Obreg%C3%B3n_pistol. I believe some early Savage semi-auto pistols did, too

  • gerald imbriale November 14, 2016, 3:37 am

    I loved my PX4 in 45acp and would still own it but for two things that almost all Beretta designs share. The safety operates backwards compared to 99% of all pistols and it resides on the slide. These two things will keep me from every buying another Beretta. The safety always cut into my hand when racking and I had to remember that it was backwards in respect to every other pistol I owned. There are low profile safeties available for it but that just makes the cutting less, it doesn’t eliminate it. The pistol was dead on in the accuracy department and 100% reliable. I didn’t notice any difference in recoil due to the rotating lockup.

  • Rumcrook November 13, 2016, 7:55 pm

    Grand power out of the Chek republic have a rotating barrel and the ergonomics are way better than the storm, mine has a nicer slide with better grooves for racking the slide or press checks. I’ve been pretty happy with mine.

  • Charles November 13, 2016, 8:16 am

    I am all for the rotary barrel action gun (there are 5 Cougars in the collection). But the twisting of the barrel eliminates usage of any barrel treatment (suppressors, compensators, ect) that will thread onto the barrel and might require future removal, or if said threaded accessory is expected to stay tight during usage without extraordinary measures – to keep it that way – (tight and/or removable) .
    I’ve spoken to the product exploration department of several suppressor manufacturers, and no one has learned of a method to overcome this problem.

  • Guns2317 November 12, 2016, 9:25 am

    Maryland State Police absolutely DESPISED the Beretta PX4 Storm and switched to Glocks in record timing by government bureaucracy standards.

    • Bill November 14, 2016, 8:12 am

      I thought all People’s Republic of Maryland governmental agencies despised all guns.

      • Douglas November 14, 2016, 11:02 am

        Now Bill, you know that all governments like guns for themselves, it is just us common folk that should not have them.

    • Kivaari November 15, 2016, 12:19 am

      What didn’t they like about the PX4? Did they have the “F” model or the “C” model? I have an “F”, it seems to recoil like a .45 yet it is only a 9mm.

    • Larry November 15, 2016, 4:27 pm

      Shoot, there’s just one more reason to buy a Beretta!

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