Wow - With ourtany hints this seems harder.
Sorry guys, I figured y'all would have had it by now.
I took that pic some years ago and sent it to my son,
who wanted to see the cartridge for a new to me rifle compared
to a cartridge he already had.
No hints, but let's review:
45 cal magnum & 8x57 - No
458 win mag & 30-06 - No
458 Win Mag & 338 Fed - No
458 Lott & 8mm'06 - No
458 Lott & 7mm-08 - No
458 Belted African Express & 7x57 - No