Was the piston supplied with the barrel when it went for plating? Is the barrel relieved around the exhaust bridge?

You shouldn't see wear like that, and certainly not with only 50 miles on them.

You may be able to dress that piston back, but impossible to say just by photos. I would seriously err on the side of caution. I would be inclined to send the barrel back to the platers with a new piston, and have the clearance checked/rectified professionally.
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Andy.
NSR-WORLD.COM

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