Italiansxs,
I haven't exited this thread, I've just been sitting back reading the replies. I didn't say that a double rifle had to be used by the shooter, I know only too well how expensive they are. All the British NE rounds can be also used in a bolt action rifle as well. Certainly rifles with bolt actions large enough to take the longest cases in NE calibres aren't either common or cheap but they are cheaper than British made doubles even if you have to have them custom built in the USA.
I stand by my original statement that there was no real need for either of the US cartridges. Unless of course it was to promote the gun makers ammo sales.
Harry