Stripped her down - very easy.

Very very dry in there.

First thing was to chop a coil off the spring, heat, and close, and dress on the grinder. I wanted to reduce the cocking effort a little regardless, so no choice there.
Piston washer was in good condition and a nice fit in the bore, so nothing to do there except a smear of moly on it, and on the front and tail of the piston. I contemplated lightening it at bit, but thought I'd do the basics first.
Made a beer can piston sleeve, lubed it all up and installed
Took a fraction off the rear spring guide OD, possibly even a smite too much, and then lubed it up and re-installed

Last thing - the bore of the plastic block that sits at the muzzle was 6.5mm - I thought that was a bit tight for a 5.5mm pellet, sitting 2 inches from the end of the barrel, on a lively recoiling pistol - so I opened it out to 7.5mm (which just kissed the crosspin, but barely). If I decide I need some muzzle weight, I'll replace this block with steel.

Reassembled and shot a few... cocking effort definitely reduced a bit, as is recoil. Power up from 3.5 to a very consistent 4.3 FP with hobbies, and the POI has gone up 3", which is good, as the weird recoil is dragging the POI down, so that effect has reduced.

I think I'll just leave it like this to be honest. I could lighten the piston, but it's not at all bad right now, so it's not crying out for it. Also it might cause issues with the trigger if I trim the outside, so would prob have to mill a couple of large slots lengthways well away from the trigger - e.g. 10 o'clock and 2 o'clock.


So there you go; not much more than a simple spit and polish is all this little beastie needs really.