Hi Ridolpho,
Kroil and hot/cold have been applied, so far without the piston coming loose. More of the same may take a long time, but patience is necessary. The gun is slightly unusual, an all matching, non-rebuilt piece. Even the stock matches, although at one time bubba slathered some varnish on it after sanding it down a bit. Rick boreckydid some extensive glue repairs at the wrist and forearm.
But it is a war veteran and the metal is in good original shape. So to complete the project I'd like to fully service the gas piston, if possible, and figure out what to do about the stock finish. Original Tula '41 finish is long gone, so now it's bare wood on the exterior (although the wood still has the asphalt smell). I may just use a few coats of raw linseed oiland call it good at this point. Unless someone has a bottle of VK-1 they don't need.