In fact, from a legal prospective, it would seem to me that manufacturers are exempt from any liability in the use of handloads.
Think of it this way. If you buy a commercial cartridge that turns out to be overloaded and you get injured by how the rifle reacts to it,..who gets sued? The ammo manufacturer or the rifle manufacturer?
You contradict yourself. The question is not whether the cartridge is handloaded or commercial, the question is if it is dangerously overloaded, regardless of whether it is handloaded or factory.
