Crosman mk.II seal issue

[762Russian]

I seem to have no luck with airguns.

Pulled my father's ancient Crosman mk.II out of storage with the hope of carrying it as a close-range gopher gun, but when I put it all together at the range and punctured the CO2 vial, the seal on the pommel piece failed and vented the gas all in a rush. So it looks like I need to change the seal.

Thing is, it is the internal seal on the puncturing mechanism that has failed... and it looks a fair bit more complex than the other seals to deal with. Advice, or a how-to guide would be greatly appreciated.

 

[leonardj]

If the end plug has the lever operated piercing setup, there is a nut that retains the seal for the piercing pin. If you look down into where the pirecing pin is located, you should be able to see two small slots on either side of that nut. You may have to grind a wide blade screwdriver to fit across the two slots. Once you remove the hut, the old seal can be dug out, and the new seal installed.

If the end plug is the push-button type, there will be a star type, spring steel retainer holding a steel plug in place. carefully use a dental pick or similar tool to lift each tab of the star just a little bit at a time until the retainer comes out. The steel plug will then just drop out, allowing access to remove the old seal, and install the new seal. To re-install the spring steel retainer, tap it flat on a solid surface, and then use a spent CO2 powerlet snout to push it back into place against the steel plug. There is a cross-slot in the steel plug that should be facing outward, in case you didn't observe it's orientation during removal.

In both end plugs, the o-ring will be a standard number 005 o-ring. Best to use 90 DU Buna, or even better, 90 DU urethane if it can be sourced.