yep sadly its the spring ring type nasty little burger

I have some jewelers screwdrivers which are being abused somewhat on this
what makes it awkward is the bleedin circlip is at the bottom of the piston carrier with only the cocking slot to access through.
As you try to lever one side the other side moves round ....out of sight of the slot....the gap in the circlip is tiny which doesn't help....and it has no 'ears' to grab hold of
what needed is 3-4 hands ...one or two to stop the dang think rotating and the other 2 to leverl the ends up and prevent return

no danger of getting circlip pliers in to this little space even if they would have a fine enough point (grrr) what an unfriendly design