Boring tapered hole

[Peacons]

Now that you mention morse #2, a reamer for that taper was my first thought to create the cavity. Though I think the morse would be a bit too long.
Have to make some measurements.
No cooking allowed either

here are the dimensions of the cartridge

 

[Silverbullet]

Dimensions look close to 1Morse taper or jarno . .400 - .551 in under 1 1/2 " easy enough to do with the compound on any lathe

 

[Peacons]

Just need a boring bar small enough to clear the small end.

 

[Janderso]

We are going to need to see that rifle.