Walksfar
Sorry for your loss.

Glad you are back

Since yu already have a 450 3 1/4" [what kind], then you already know about the many choices of .458 bullets.

For low cost plinking bullets the Remington 405 gr are hard to beat. I have not loaded for the 458 Lott, but I have had 2 458 Wins and I used IMR 3031.
I also use 3031 in my 450 No2 double for 350 gr Hornadays.

Have fun with your new rifle.