Well, I won't speak for tonnage pressure wise, but lets look at the era. Many of these cartridges were comming off of the old blackpowder setups, and pretty rapidly. Cordite was the new standard, adn mechanisms were being advanced. An friend of mine asked why I would choose a sxs .318 or .400 nitro over a bolt action magnum. I told him that back in the day, a double gun not only meant you had a quick back-up shot, but that you had TWO INDEPENDANT MECHANISMS-which meant less of a chance that both would fail at a critical moment. In one on one human combat, if technology fails, you can bash the other fella with whatever you have. If you fall to a charging animal, their sense of self preservation is stronger, and you need to deliver a killing blow before they are close enough to get you. Anyway, Holland and Holland actions are "idiot proofed" (not my term), so if it happens that a very strong load gets fired from them, gun damage may happen, as well as shooter damage-but not from the gun separating. There is a rumor of them not being able to keep the action together on their prototype .800 nitro express as of yet, at least after replicating the newer surviving 2-bore cross locking mechanism...maybe they should make it a cordite only cartridge...
