Ms460 hole in piston crown

[jk14]

I wonder if the piston crown got damaged by a metal stop some time in the past. Perhaps using a 10mm bolt in the decomp? (I'm unfamiliar with the saw so I don't know if that is possible).

Once the crown got damaged, with a bit of raised metal to absorb heat and some hair line fractures in the crown, the piston became susceptible to a melt down.

Is that melted aluminum under the piston crown?

Yes it is. I believe that is what happened.

 

[CR888]

In the first pics posted with a close up shot of the damage, the hole appears to have a definate hexagon shape to it just like a hex key. I know some of the piston stops are hex in shape......