Quote Originally Posted by pumpygun View Post
It's the old snap on connector. I've never heard of filling the cylinder from the base end. This could be a short term solution as I need the rifle for a week's time!
Correction, the refill adapter that came with my Mk 2 (AA/CZ T200 Target rifle) is THIS one. It fits into the DIN outlet of a HPA cylinder, the removable S200 cylinder screws into the adaptor.

Sounds like the suggestion from gc93 covers the issue you have with the old snap on connector.