Good for picking a product that actually works on passivated metals. However, you also bought an upper made of 7075. There is absolutely no need for a retaining compound unless the barrel extension to upper extension is loose, then you would be better off thermofitting. But I doubt that will be the case. You can safely torque a 7075 upper into the upper end of the "mil specs" and in fact past it to at least 100 ft-lbs without any worry. Most of mine are in the 80 to 100 pound range. It is also what we suggest for our barrels (7075 receivers and 80 to 100 ft-lbs of torque).