smallfry

As Bwana-be says, the Lazzeroni is slightly smaller than the 416 Rigby case and Lazzeroni confirmed that to me in an email. In other words, not from a book of cartridge specifications.

Actually Lazzeroni is the opposite to the Remington Ultras...they are slightly bigger than the 404 Jeffery case.

Mike

Not quite. More like a 470 NE rimless.
The base is ~.577" IIRC, and the Rigby is ~.592"?
Pretty close though. The Rigby (better yet, Lapua) trimmed to 2.8" COL (better yet 3.1") would beat the Lazz when all else equal, though I hear he loads his ammo to some insane pressure like 67k psi.