I have my late father's Crossman 600. Unfortunately, the seals are shot, and it dumps Co2 as soon as you pierce the cylinder. He was on a shooting team, and used the 600 to practice in the backyard. I really need to either fix it myself or send it off for repair.
That’s a shame.
One of mine was sent out to Crosman in the late 1970s to have the seals redone. Still have all the correspondence from that in the box.
The other just keeps on working fine!
They are still in business!
Maybe Crosman will still service the 600! Worth a try!