458 ai

[Peter hunt]

Can someone please tell me the mother case for this calibre is it 458 WIN MAG or 458 Lott and any load data would be helpful all replies welcome thank you

 

[IdahoSharpshooter]

easy, just measure the case length.

 

[MClark]

I looked in Ackley's book.
There is a listing 450 Magnum (Ackley). It is a necked up and fire formed 375 H&H case. Says it's a straight taper like a 38/55 and not the tiny shoulder like a Watts.
The Lott came about years later. Had a gun writer to promote it so earlier cartridges disappeared.
Starting Loads would be similar to the Lott, the book lists loads but Ackley's data tends to be HOT.