Are Glocks a blow back design or not?

Discussion in 'General Glocking' started by flw, May 19, 2013.

  1. flw


    Question is are Glocks a blow back design or not?

    If not, what is it?

    I've always assumed they were but then I thought to ask.

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    #1 flw, May 19, 2013
    Last edited: May 19, 2013
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  3. bentbiker

    bentbiker NRA Member

    Only the .380 models are blow back designs. The rest are locked breech.

    #2 bentbiker, May 19, 2013
    Last edited: May 19, 2013
  4. GlocksterJeff

    GlocksterJeff Glock Armorer

    Basically a blow-back design uses only the mass of the slide and the compression of the recoil spring to hold the cartridge case in the chamber long enough for the bullet to leave the barrel, thus allowing the high gas pressure to vent. A locked breach design (Glocks and most other pistols for 9mm and larger cartridges) locks the barrel to the slide for a few instants during the first few millimeters of rearward travel. The barrel and slide travel locked together long enough for the gas pressure to subside.
    #3 GlocksterJeff, May 19, 2013
    Last edited: May 19, 2013
  5. flw


    So what component is holding it back for a millisecond or so?
  6. Backward travel (with slide and barrel as a locked unit) against the recoil spring assembly.
    #5 SouthpawG26, May 19, 2013
    Last edited: May 19, 2013
  7. All Glocks (except .380) use a modified Browning locked breech short recoil operating principle to fire. Later Glock 19's are a semi locked breech but are still not blow back operated.
    #6 PattonT, May 19, 2013
    Last edited: May 19, 2013
  8. Yeah, only the 380s are blowback.
  9. Can you expand more on the "semi locked" concept?

  10. bentbiker

    bentbiker NRA Member

    Your best bet to see this is to place the barrel (without the slide) on the frame with the front lug up against to the slide lock. You'll see that the rear lug sits on the locking block and can't drop. As the slide and barrel move rearward together, the rear lug passes the locking block, and the front lug hooks under the locking block and pulls the rear of the barrel downward out of the opening in the slide. The locking block then stops the barrel's rearward motion, opening the ejection port as the slide continues back. As the slide comes back forward, the slide pushes the barrel forward, and the rear lug again rides up onto the locking block raising the barrel into the locked breech position. The slide/barrel assembly stops its forward motion when the front barrel lug once again locks into the groove in the slide lock.
  11. The barrel locks to the slide via the ejection port. Both the slide and the barrel move backwards together for approximately 4-5 mm, with the barrel still locked inside the slide's ejection port.

    Then the barrel lug hits the back side of the locing block and is forced downwards, coming out of the ejection port, and the slide continues rearward extracting the case from the breech of the barrel.

    By the time the locked barrel and slide assembly have moved back that 4-5 mm locked together, the bullet has exited the barrel and pressures have dropped to safe levels.

    Here's an animation:
  12. Arc Angel

    Arc Angel Deus Vult!

  13. Lockback

    Lockback Polymerlicious!

    What he said.
  14. HKLovingIT

    HKLovingIT Resident Evil

    Check it out:

    [ame=""]Glock Function Animation - YouTube[/ame]

    [ame=""]Makarov pistol "PM" (full disassembly and operation) - YouTube[/ame]
  15. bentbiker

    bentbiker NRA Member

    Since we have the video of the Glock interactive animation above, does anyone know whether the original interactive version is still available anywhere? It used to be owned by TGScom, and was available at When TGScom went out of business about one yr ago, the interactive version disappeared entirely as far as I can tell.

    I'm not looking for the version -- I want the original of the embedded one above, with the checkboxes.
    #14 bentbiker, May 20, 2013
    Last edited: May 20, 2013
  16. OldSchool64

    Platinum Member

    Isn't there at least one blow-back design 9mm? Granted it wouldn't have been very successful but it seems like there is or was such a thing.

    I'm talking about 9x19 Parabellum, not 9x18 Makarov.
    #15 OldSchool64, May 20, 2013
    Last edited: May 20, 2013
  17. Astra models 300 400 600 700 etc.
    were blowback 9mm
    #17 dizmodeus, May 20, 2013
    Last edited: May 20, 2013
  18. Bello

    Bello America/Italia

    I think the high points 9mm is blow back but could be wrong
  19. One thing you should know is that the bullet has already left the barrel before the slide begins its rearward travel. Many people think that by the slide moving rearward and the casing being pulled out of the firing chamber, some gas pressure is lost and therefore, bullet velocity drops off. But the bullet is long gone before any of this happens.

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