After a brief discussion on another forum about copper tubed boolits, I decided I would dismantle a vintage cartridge to see for myself.

I have a quantity of Eley 450/400 2-3/8" BPE cases and pulled apart one of the rough ones.
Here is what I found...

The PP boolit is 230grs.
The paper is .001" with two wraps.
Wrapped dia. is .401" +/-

The tube is .155" in dia. and .515" long

Three wads below the boolit.
.025" - .100" - .025"
80grs of black powder

Inside the base of the case is raised and I cannot see where the primer spark would travel to the powder charge.
Will have to take a closer look...