Like the CZ 52 the HK P7 series of pistols has an operating system unique in handguns. The following is my attempt to explain how this pistol works based on my examination of it. If I am incorrect in anything please correct me.

The field-stripped pistol

The piston pinned to the slide travels within this tube when the pistol is assembled and fired or the slide is pulled back manually.

This is the chamber of the barrel. A cartridge would be in here with the pistol assembled, ready to fire. In pistols of larger calibers (larger than about a .380ACP) the breech most stay closed until the slug exits the barrel for the safety of the shooter. When these pistols are fired the slide and barrel ususally travel rearward as one unit for a short distance before separting to eject the spent casing and feed a new round. P7 series pistols use a different method. These have a fixed barrel like pistols firing weaker rounds (.22LR, .380ACP, .25ACP, etc). The slide and barrel are never locked together in a P7 pistol.
So how does the breech stay closed? When the pistol is fired gases force the slug out of the barrel. Some of those gases travel through the gas tube port (see photo above). That slide-mounted piston you saw in the previous photo is in the gas tube as well. The gases push on this piston and therefore push on the slide since they are pinned together. The slide/piston assembly is pushed toward the front (muzzle end) of the gun, stopping it from recoiling toward the shooter. This all works until the slug exits the barrel. At that point there is not enough gas pressure to stop the slide/piston assembly from recoling rearward, Now it travels back and ejects the spent casing. The recoil spring returns the slide/piston assembly forward to feed a new round, assuming the magazine is not empty.
Some of the gases also travel through the flutes in the chamber helping to push the spent casing rearward once the breech opens. This aids in ejection and the pistol is reported to operate with the claw extractor completely removed.
The system works very well (my P7 has had not a single issue). However, there are drawbacks. The gases foul the gas tube and piston and heat up the frame of the pistol quickly.
The P7's are not gas-operated in the sense that many rifles are (AR-15, AK-47/74, many others). In fact the P7 gas operation does the opposite of that operating those rifles. Gas pressure in the P7's stops parts from moving. Gases in the rifles are used to make parts move.

Piece A in the photo above is attached to the squeeze cocker. Piece B is attached to the firing pin. When the shooter squeezes the grip Piece A moves back. This in turn pushes Piece B back, thus cocking the firing pin back.

This photo shows Piece A with the squeeze cocker engaged. Piece B would now be back if the pistol were assembled, compressing the firing pin spring. Pulling the trigger lowers Piece A which allows Piece B (the firing pin) to travel forward under the pressure of the compressed firing pin spring. The firing pin strikes the primer of the cartridge in the chamber. Now everything I explained above occurs. The shooter does not need to release/resqueeze the cocker for each round fired, only keep it squeezed and pull the trigger to shoot. Without pressure on the squeeze cocker the trigger does not work and the firing ping spring is not compressed so the pistol is rendered completely nonfunctional and safe, even with a round in the chamber. Look below for photos of the firing pin assembly.

Once the magazine is empty the follower will push up the slide catch to lock the slide back, a method common to most all semiautomatic pistols.

The slide catch can be engaged manually if there is no magazine in the gun by pushing this little button rearward. It's almost unnoticeable.

This shows the squeeze cocker engaged. The back of the firing ping protrudes slightly from the back of the slide, a clear indication to the shooter that the pistol is armed.

Piece B is attached to the firing pin. To remove the firing pin assembly a tool is used to rotate is 90 degrees which locks Piece B back. Refer to the next photo to see this assembly as it looks when installed in the pistol.

This is how the firing pin assembly looks installed in the pistol without the squeeze cocker engaged. Engaging the cocker would pull Piece B straight back and compress the spring.

With the firing pin assembly removed you can see straight down the barrel. Look to the right and you will see the firing pin assembly on top of the voice recorder. Next to that is the firing pin assembly removal tool (with the 2 big holes in it). This tool can also be used to remove the grip panels, something I have not yet done.

When the squeeze cocker is released there is a loud "click". That can be avoided by pressing up on this little button behind the trigger guard at the top of the cocker. It is not visible when the cocker is not squeezed. It is very recessed. Just put a finger tip on it and apply pressure. You will know when it releases. The cocker may pinch your finger a little. Once this button is released you can ease the cocker (thereby the firing pin) forward.
This page was last modified on 06 September 2010 19:27