Gentlemen, not be be "snippy", but I'm not a "new boy on the block". I've built 6 double rifles already. I have fired many thousands of rounds through those rifles safely. I understand metallurgy, hoop strength, etc. What is amusing is that there are critical posts here from guys who have been sending me personal e-mails for years, asking my advice on how to do this job. Suddenly, everybody's an expert! The combined wall thickness of my mono-block and the barrel stubs is .245", most of that being the best, modern, 4140 steel. After shrink-fitting the barrels into the mono-block, I had their rear faces micro-tigged to the mono-block, so nothing short of dynamite is going to move them. My regulation load is a 140 grain Nosler Partition at 2200 fps. That load will produce well under 40,000 psi. My proof loads are the same bullet at 2650 fps. Three of those loads, fired remotely through each barrel, will tell the tale. I'll post some more photos in a day or two when I have the time.