What is the OAL of a 450 Rigby cartridge and a 458 Lott cartridge?

Dr. Ken Howell gives the brass length:

450 Rigby: 2.8937"
.458 Lott: 2.8000"

Add a generous 0.850" to this for the bullet nose beyond the cannelure, though most will be 0.830" or less:

450 Rigby: 3.74"
.458 Lott: 3.65"

You see that both will fit the CZ box.