The transient charge thingy was a BSA excuse, see my oher thread, for it leaking over a few days down to mistakes they made. I have no idea if it is still possible to get the cylinders as a spare. Check with Chambers, or Knibbs if you are feeling flush. It just one of many things JB sorts and improves when he services and upgrades them. He also works on the trigger and barrel. I will try to find out when the Firebird was launched. JB was asked to do a fixed barrel version of the Spitfire (Firebird) for target shooters who wanted to use long scopes that were popular then but didnt work with the breakbarrel Spit.