G'Day Fella's,

Yumastepside, the highest (Factory) pressure cartridge on a No 4, that I know of and is fairly common, is the .308Win/7.62 NATO.
The largest (Big Bore) that I have heard of, is the .444 Marlin.
It is not common but not unheard of, here in Australia.

Looking forward to other, more knowledgeable persons posts!

Hope that helps

Doh!
Homer