The REASON you can safely fire .458's in a Lott is due to the chamber shape. Normal chambers have a sharp step, then a 45 degree angle to the leade at the front end of the chamber, not so the Lott. The Lott has a gentle slope, much like a handgun's chamber instead of the 90 degree step and 45 degree aslope.

Shooting .458's in a different long chamber, as in the .450 Watt's will result in guidling metal being shaved off into the chamber itself - not a good thing as the bullet jacket material will weld itself to the chamber and be difficult to remove. Removal of the excess material will be necessary before being able to safely shoot full length ammo again. As noted, this won't happen in the Lott (or handgun) chamber.

Coupled with shaved brass in for instance the afore mentioned Watt's chamber, because material is removed, a weak spot will result, not to mention the accuracy problems - again, not so in the PROPER Lott chamber.

If a calused gun smith simply uses an old unaltered Watt's reamer to chamber your Lott, it will not have a true Lott chamber and therefore will shave jacket material if short ammo is fired. Dave Kiff at Pacific can re-grind the Watt reamer's to cut a true Lott chamber.