Advice please

[Round]

Mercury .....Anyone removed a jammed piston head from a cylinder and how ?

[bill57]

If it was me, I'd probably start by removing the barrel, then putting a thin parallel punch through the transfer port and tapping it gently to see if the piston head is going to move. If it does move, you're on your way.
Bearing in mind that the port is probably not central, there is a chance that, if the piston head moves, it may tip and jam. It might be worth putting the piston down the cylinder in reverse to hold the piston head square to the cylinder bore.

If you can't face removing the barrel, then it's a very long thin punch you'll need.

[El Garro]

I'd get some solvent in there for a bit first.
Petrol or Mek will do if you take the usual safety precautions. The cylinder can be wrapped in old rags to slow the evaporation . It should come out easier after that.

[bill57]

Is it just the piston head (ie. washer assembly), or is it the whole piston?

[Round]

Just the head.

[ggggr]

As has been said, you can try a bit of solvent in there to try to loosen things up. It could be a nylon head or an alloy one, but the buffer washers go like old elastic bands.
After the solvent (if you use it), clean out as much of the cylinder as you can and get some lube down there. Then I would try 2 rods to shift the head. A thin one through the transfer port to push on the head, and a thick one (about the diameter of the spiggot on the piston) to go down the cylinder into the head. You are highly unlikely to shift it with the thin rod alone as the transfer port is off centre and the head will turn and jam. With the thicker rod in the head, you wangle it about as you are pushing with the thin rod and, hopefully, you should be able to "Walk" it down the cylinder as far as the cocking slot, where you can start to lever it.

[look no hands]

I had this problem a few years ago (one of the main reasons I always change the internals as soon as I get a Merc/Airsporter), I soaked the head to loosen it up and ended up using a very long thin screwdriver that went down the transfer port and I managed to beat it down the bore, you could try using compressed air down the transfer port to see if that may dislodge it, you could also try a long rod with a screw on the end and try to screw it into the bottom of the head and then pull it out like a slide hammer.

This is why I always recommend changing the internals even if it seems to be shooting ok.

Pete

[Round]

Thanks for all the help lads.. I reckon it's a ally one.