Thank you for the thread, Ben. It is always most informative when one goes to a primary source for information, even if it means dissecting things.

The copper tube in this .400 bullet is smaller than the ones I have here for a .450 or .500. They measure .204 diameter by about .600 long, IIRC. Another member here most kindly sent me some samples that came in a little cotton bag in a cased rifle set he had purchased. The weight difference in the projectile is 40 grains, so the 270 express bullet in my rifle becomes a 310 solid with a flat nose pin.

Do you think the patcher lady may have just pressed the base of the bullet against her thumb, and just twisted it a little, to do the patch like that?

Is the bullet tapered?

Also, do you think the lacquered wad may have been loaded wet, so it would dry and seal/waterproof everything?