locked breech vs blowback

This is a discussion on locked breech vs blowback within the Defensive Carry Guns forums, part of the Defensive Carry Discussions category; Not being a trained or self-taught gunsmith, I'm pretty much in the dark on exactly how semi automatic pistols operate. I just keep mine field ...

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Thread: locked breech vs blowback

  1. #1
    Member Array 1gunsnowbird's Avatar
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    locked breech vs blowback

    Not being a trained or self-taught gunsmith, I'm pretty much in the dark on exactly how semi automatic pistols operate. I just keep mine field cleaned and when it comes to my Glock, I'll occasionally break it down a bit further in order to clean the channels for the striker and the extractor, etc.

    My question is this: do locked breech guns provide any advantages in terms of reliability compared to blowback designs? Just what are the relative merits of both designs? Is there a major difference in recoil? Are certain calibers inherently better suited for one system or the other? What are popular examples of each?

    Any other observations would be appreciated. Thanks.
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    Member Array TxCommish's Avatar
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    I've always heard that blowback is better suited to smaller calibers and locked breech for the bigger ones. YMMV.
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    Here is an article that may provide some insight as to the differences.

    Semi-automatic pistol - Wikipedia, the free encyclopedia
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    In regards to handguns the blowback design holds the breach closed by the strength of the recoil spring and mass of the slide, a locked breach holds the breach closed due to the alignment of locking lugs between the barrel and slide or barrel and frame. The blowback design is simpler, however as the power of the cartridge increases so must the strength of the recoil spring and the mass of the slide. A locked breach design allows for the use of a more powerful cartridge in a smaller package than does the blowback.

    Blowback




    Locked breach

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    locked breech designs are usually used in calibers 9mm and above (in power). blowback, or straight blowback is most often used in .380, 9x18, and below. as sgb said, the blowback design is simpler. in practice, locked breech designs are just as reliable.

    my personal experience is that for the same power level, locked breech designs transmit less recoil to the shooter, because the design itself absorbs some of the recoil. to me, the 9x18 cartridge, fired in a steel Makarov pistol - a blowback gun, 'kicks' as much as the more powerful 9x19 in a polymer-frame Glock 19, which uses the locked breech design.

    most locked breech designs use mechanical methods to delay the slide movement - thus the lugs beneath the barrel on these guns. a few pistols, like the H&K P-7 series, use a gas system to retard the slide's rearward movement. a hole in the bottom of the barrel channels some of the expanding gasses into a section below the barrel to lock the slide in place until the bullet has exited the barrel, and the pressure drops. this system also attaches the barrel to the frame like a blowback design, and has the potential to increase accuracy because the barrel doesn't move rearward during recoil. this design also allows for a very compact pistol.

    i've read that the Kel-Tec PMR-30, which fires the .22Magnum cartridge, is designed to be both blowback AND locked breech capable, depending on the power of the ammunition. i don't know how this is done.

    a few .380's, like the Sig-238, use a locked breech design, and this accounts for why the 238's slide is so much easier to manipulate than that of a blowback .380 like Sig's own P-232. the 238's recoil spring can be less stiff because it doesn't have to retard the slide movement at the moment firing occurs.

    blowback advantages: simpler. more compact. take-down usually easier. greater accuracy potential.

    blowback disavantages: transmits more recoil for a given power level. not really suitable for cartridges more powerful than .380 because the necessary slide mass and strength of the recoil spring are so high.

    locked breech advantages: allows use of more powerful cartridges in a package just slightly larger than a blowback design. quite reliable when properly designed and manufactured. design absorbs some of the recoil.

    locked breech disadvantages: more complicated to make. takedown more complicated. usually results in a slightly larger gun. possible loss of accuracy potential.

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    VIP Member Array ghost tracker's Avatar
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    In higher powered pistol calibers, the recoil spring can't be made strong enough to hold the breach closed while still being weak enough to allow hand/arm strength to manually cycle the slide, so a blowback can't work. The breech must therefore lock itself into battery and release after the recoil impulse to assure that the vast majority of the firing pressure (power explosion) is used to expel the bullet out of the barrel. That's what J.M. Browning's 1911 "link" provides.
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    VIP Member Array Superhouse 15's Avatar
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    Quote Originally Posted by ghost tracker View Post
    In higher powered pistol calibers, the recoil spring can't be made strong enough to hold the breach closed while still being weak enough to allow hand/arm strength to manually cycle the slide, so a blowback can't work. The breech must therefore lock itself into battery and release after the recoil impulse to assure that the vast majority of the firing pressure (power explosion) is used to expel the bullet out of the barrel. That's what J.M. Browning's 1911 "link" provides.
    You can make blowback guns in larger calibers, but they are heavy, large, and awkward. For example check out the fime products made by Hi Point...

    The H&K VP70 was a blowback in semi and full auto and not too obnoxious (except for the trigger). A polymer framed, striker fired, high capacity pistol with unique combat sights and a version available as a machine pistol, and a commercial flop. Glock nailed that a few years later, and compactness, looks, and quality trigger was the difference.
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    VIP Member Array ghost tracker's Avatar
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    Whoops! Maybe I should have said "...blowback designs can work with a slide that's big & heavy & chunky/clunky enough".
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    Member Array 1gunsnowbird's Avatar
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    Thanks to you all for your information. That helps me in my quest for a pocket pistol that might actually work !!! I fell in love with the concept about 6-7 years ago but have been sorely disappointed in the reliability of the half dozen models of .380 ACP from just about every major manufacturer and all of them were locked breech weapons.

    Even though I swore these little semi autos off for life, I find myself weakening as I learn more about the MasterPiece Arms .380, which is a blowback design. Your responses also help me understand why they recommend changing the recoil spring every 200 rounds. I will assume that if I purchase one, once I've broken in and seated all the parts, and if it proves reliable, then it might make a good BUG or deep concealment weapon in an ankle holster or pocket holster, when my G26 Glock is just too much for certain occasions.

    Thanks again.
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    New Member Array TheBossOfu's Avatar
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    Snowbird: take a serious look at the Taurus TCP. Its a blowback .380 She has a lot of real nice features. Stainless barrel and ejector. 170 ejection port . Light weight , accurate , well made, great warranty and will run you about $250. Mine gets a lot of pocket time! I have never had one problem...ever! That little thing will digest any ammo you feed it. She needs a quality pocket holster as there is no manual saftey , or mag disconnect.

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    Function and operation has pretty much been covered. Generally you will have more felt recoil with a blow back design pistol, IMO.
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    Senior Member Array bunker's Avatar
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    Quote Originally Posted by Superhouse 15 View Post
    You can make blowback guns in larger calibers, but they are heavy, large, and awkward. For example check out the fime products made by Hi Point...

    The H&K VP70 was a blowback in semi and full auto and not too obnoxious (except for the trigger). A polymer framed, striker fired, high capacity pistol with unique combat sights and a version available as a machine pistol, and a commercial flop. Glock nailed that a few years later, and compactness, looks, and quality trigger was the difference.
    Thank you, i like mine very much.
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    Senior Member Array bunker's Avatar
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    Quote Originally Posted by ghost tracker View Post
    Whoops! Maybe I should have said "...blowback designs can work with a slide that's big & heavy & chunky/clunky enough".
    My girlfriends hair dryer is smaller than my blowback High point 45 acp, but hey, it works every time. bunker
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    Member Array 1gunsnowbird's Avatar
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    Again, thanks for the input. ThebossofU, I'll take a look at the Taurus at your recommendation. I think I'll also take a look at the 380 poll/survey on this page and see if there's any consensus or at least a clear winner. It's great to have the neutral feedback of strangers with no visible axe to grind or ties to any one particular manufacturer. I think this is the best way to thoroughly examine a potentially life-saving decision like this, so I appreciate your time and thoughts very much.

    Still not sure if this is the way to go, or just try to adapt to the extra weight and thickness of my Glock 26 ... I know a couple men who carry G27s in an ankle holster and they've been doing it for years as LEOs, so I guess ANYTHING can be done if one wants to deep conceal a handgun. As of now, my Galco Second Amendment AIWB holster has earned the primary function of concealed carry for some previous G27s and G26s. Maybe I'm getting a bit anal about even considering something smaller and lighter.

    Take care.
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