Head gasket blown again! Second time in two months. I’ve had problems with 3 different barrel and head combinations. The only common factor is me and the antifreeze/coolant I’ve used. I’m gonna guess it’s not the coolant 
Weird thing is every single time it’s failed on the top/head side of the gasket. Between the head and gasket surfaces. Never between the gasket and the barrel...
This is the first time this combo has failed (3mbP head & barrel) and I never removed the studs to clean the top of the barrel (because I had a stud shear off on my last barrel) It’ll be interesting to see which side of the gasket failed this time...