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Posted: 12/6/2025 3:07:55 AM EDT
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This is a licensed Glock 17 Gen3 or 4 replica, it is probably 10 years old. This GBB gun uses an internal hammer, the hammer pushes a valve knocker against the gas outlet valve in the back of the magazine. Gas is contained in the magazine and is released when the knocker opens the gas discharge valve. The knocker lock keeps the knocker holding the gas discharge valve open for more time during slide travel, this makes function more consistent. Eventually the slide runs over the top of the knocker lock, depressing it and allowing the knocker to return back against the now cocked hammer. The top of the knocker lock broke off, so the slide would not depress the lock and release the knocker. Because the knocker continued to depress the magazine gas discharge valve, all the gas in the magazine would discharge on the first shot after charging the magazine with gas. The slide would cycle very quickly during the discharge. Removing the knocker lock, causes the valve knocker to move with the hammer, as normal, during the hammer falling, and to discharge gas to fire the gun. But, when the slide runs over the hammer and cocks it, the knocker follows the hammer back to the knocker retracted position. The valve knocker isn't trapped in the open the valve position for a short time when the hammer is cocked by the slide, and then, after that short time, the knocker gets released to retract back against the hammer. It's not a short time so much as it is holding the discharge valve open for more of the slide travel cycle and thus providing gas to cycle the slide in a more uniform and consistent manner. Not having a knocker lock installed causes gun slide function to vary some with gas pressure changes in the magazine. In slow fire the difference is hard to notice. In rapid fire, gas in the magazine undergoes gas expansion cooling and accompanying gas pressure decrease, so the difference probably is noticeable. I shoot a G17 in 9mm, with a 22LR conversion and also the GBB G17. The similarity in shooting is amazing. These are the Good Old Days. |
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