This article will walk you through how to remove and replace your DMK22's firing pin.
Required Tools
- 2.0mm allen key
- 1/16" punch
- Staking Tool or equivalent steel punch
- Hammer
- Bench block
- Degreaser
- Blue threadlocker
Separate Bolt from the Guide Plate
With the bolt removed from the DMK22 upper, manually retract the bolt to expose the bolt retaining screw.
Remove the screw using a 2.0mm allen key. Maintain control over the bolt as it is under spring tension from the recoil spring.
Once the retaining screw is removed, carefully slide the bolt off the guide plate. Note how the recoil spring is seated in the rear of the bolt. Then, set aside the guide plate and bolt retaining screw.
Remove the Firing Pin Retaining Pin
Set the bolt down on a bench block. Using a 1/16" pin punch, drift out the firing pin.
Directionality does not matter and the pin can be drifted out in either direction.
It is not necessary to completely remove the firing pin retaining pin. It only needs to be removed a little more than halfway.
Remove the Firing Pin
Remove the firing pin and spring from the rear of the bolt.
If the spring does not come out with the firing pin, use a small pick or other tool, or lightly tap the bolt on your work surface to dislodge the spring.
Inspect the firing pin channel for any debris or other contamination. Clean if necessary.
Install the Replacement Firing Pin
Place the firing pin spring onto the forward end of the firing pin, then insert it into the rear of the bolt. The notch in the firing pin is to point toward the top of the bolt.
While applying light pressure to the rear of the firing pin, begin reinstalling the firing pin retaining pin. Use small, light taps, stopping periodically to check that the firing pin can still move smoothly in and out.
If the firing pin binds at any point while installing the retaining pin, stop. This means that the firing pin is not in the correct position relative to the retaining pin. Partially remove the retaining pin, recheck the firing pin's orientation, and try again.
Stake the Firing Pin Retaining Pin
After the firing pin retaining pin is set, we highly recommend staking the hole on the left and right sides of the bolt to prevent the retaining pin from "walking" during operation and causing a malfunction.
This involves using a staking tool, or pointed steel punch, against the edge of the hole so that some material from the edge partially occludes the hole.
Reinstall the Bolt
First, degrease the bolt retaining screw and the associated threading in the guide plate. Apply a small amount of blue threadlocker onto the retaining screw.
Place the recoil spring into the rear of the bolt and slide the bolt back onto the guide plate.
While holding the bolt compressed to the rear of the guide plate, reinstall the bolt retaining screw.
The DMK22 bolt is now complete.