Thanks for that, turk. I checked and it's good, if we agree that it is set to the space between the rod and the top, not the bottom of the rifle. But I had it out at the range today, and really went through the process deliberately. I could never recreate the problem intentionally. Different ammo, brands and .223vs5.56. Different factory mags. I left the range not really further ahead. So I get home and give a good cleaning and once over, then I see something. I have a stainless mini in a synthetic stock. No marks are present on the mini or its components, but low and behold, I find slide marks on the stainless heat shield in the stock just below the 'piston'. Not easily fixed to me but what do I care? I used a punch and knocked it in a bit. Range report to follow-hopefully next weekend.
