I've been hit with two of those types of lawyer notices over the years. My reply was, "pound sand", and then never heard another word. We're in the software industry and the big guys sometimes think they can control what bits and bytes you type into a system to do X function, which they can't so long as you are creating the code yourself and not swiping someone else's. Not sure how that would translate to what is essentially a replacement barrel for a rifle, but doubt Blaser has a patent on the rifle barrel, don't imagine anyone does. Making an aftermarket part or bolt on for things is pretty common for a lot of manufactured products, i.e. cars, motorcycles, computers, etc. If barrels were treated differently than other bolt ons or replacement parts, Remington, Winchester, Ruger, and every other manufacture would have shut down the small firms making these year ago, at least you would think they would have.