I bought the 600 way back in 1963. It has been sitting in the box unused for a majority of those years. I recently decided to take it out of the safe and see if it was still operational. I inserted a Co2 cartridge and capped it and when I pierced the cartridge, the gas immediately leaked out, which was not unexpected. I found detailed disassembly instructions on the internet and ordered a seal kit from Ebay. I do small modifications and repairs to my cartridge and muzzleloading firearms so I decided to replace the seals in the 600. Thanks to the instructions all went well until I had to remove retainer pins that hold the rear valve in the inner tube. I threaded a 6 x 32 screw into the first retainer and it came out as described in the instructions. I threaded the screw into the second retainer and became very unhappy when the screw twisted/broke with the pin still firmly in place. I'm looking for suggestions on how to handle this dilemma. I am ready to send the part out for repair should that become necessary.