The .458 Lott was different from the .450 Watts(identical chambers - almost), in that the front of the chamber of the Lott had a gentle entry into the throat, instead of the normal 90degree chamber ending and 45 degree angle into the throat itself, that the .450 Watts & all other chambers have.

Thus, the Lott chamber was meant to be able to shoot .458 Win. Mag. without shaving guilding metal or copper off the bullet's shank as would happen to the bullet as it hit the end of the .450's chamber.

Will it shoot accurately? There is only one way to find out as well as finding out how much velocity is lost due to blow-by.

Postman's suggestion to use .458 Lott brass is a good one.