I’ve spent a bunch of time lately to looking at how the guns I have actually work. They are fascinating machines. They range from the very simple Glock to the far more complicated Beretta.

In the end, like I’ve said before, it’s all machines that are made by man and are intended to be serviced by man. (Or woman as it could very well be.)

And guns are just that: machines.

The theory of operation of the Glock can be put down in just a few steps (I’ve never seen it put down like this):

  1. Pull the trigger deactivating the trigger safety
  2. As the trigger moves the trigger bar the firing pin safety gets pushed up in its channel. (The ramp you see on the trigger bar on a field stripped Glock is what does the work there)
  3. The trigger all the while is connected to the firing pin at the back of the cruciform. Eventually the back bit of the trigger bar gets to the connector and drops the sear down releasing the firing pin.
  4. The firing pin hits the primer and sets off the chain reaction to get the bullet out the barrel.
  5. Every action, having an equal and opposite reaction, causes the shell casing to push on the breech face on the slide. This causes the slide/barrel assembly to slide back.
  6. After the bullet leaves the barrel the locking lug on the barrel hits the locking block on the frame. This causes the barrel to pivot down unlocking it from the slide. It’s normally held there tightly by being stuck in the slide’s ejection port. (Incidentally this is the same as on Sigs with the tilting barrel design… originally the disconnecting barrel was made by John Browning on the 1911)
  7. The slide continues back due to inertia with the extractor holding on to the case.
  8. Eventually the slide goes all the way back to the ejector. This makes the case pivot out of the extractor — flung to the right.
  9. While the slide is going back there’s a little cam machined onto the bottom of the slide. This nudges the connector inward a bit and releases the sear (the back-most bit of the cruciform on the trigger bar).
  10. The slide come forward again because the recoil spring is pushing it back.
  11. On the way back the stripper on the bottom of the slide grabs another round from the magazine and feeds it into the chamber.
  12. The firing pin lug comes to rest on the sear and resets the trigger mechanism. (If you have your finger off the trigger, this is what pushes the trigger forward again.
  13. The round gets chambered by the breech face and the extractor hooks on.

This is such a simple cycle. It’s so much simpler than the double-action/single-action of a Beretta. I’ll see if I can diagram that out some time later.

The cool thing is that you can look at it yourself if you have the gun field stripped. Nothing is hidden from view.

To field strip a Glock you’ll be around step 8 above. The trigger bar is still down because you needed to dry fire the gun. Since there’s no round in the chamber (really, check before you think you dry fire so you don’t live fire!) the cycle doesn’t really happen. What you can do is act the the part of the slide yourself.

You can nudge the connector inward (towards the left of the gun (top in the picture)). The trigger bar will snap up — that’s what’ll catch the firing pin lug later in the cycle. Then, while applying some rearward pressure on the trigger, slowly push the trigger bar up using the firing pin safety. Eventually the trigger will go all the way forward and the trigger safety can engage. At this point you can let go of the trigger pressure. The trigger will stay there due to the trigger safety even without you pushing forward on the trigger bar. (Congrats, you tested the trigger safety!)

Then (still applying forward pressure to the firing pin safety ramp) you can pull the trigger back. You’ll watch as the trigger goes back down the ramp on the connector. If the slide were in place at some point the firing pin lug would loose touch with the trigger bar as it went down the ramp. The firing pin would snap towards the primer, past the now open firing pin safety setting off the charge.


That’s all she wrote!

So damn simple!