I am thinking about 30 rounds is the recommended interval for cleaning of a mixed fouling with gilding metal, brass/bronze, and copper-monometal bullets. Daisy was tried with a pin gage when she was so fouled. .450" would not pass her muzzle. .449" would enter and catch on the fouling a few inches down the barrel. So the Ruger No. 1 .458 WM might be a true .450"-bore by pin gage, and .459"-grooved by slugging when clean.
I still say that the cleanest shooting ammunition that I know of is duplexed BP under a grease cookie and a paper-patched lead bullet. Self-cleaned by the paper patch with each shot. The .458 WM is ideal for those if allowed to be loaded Long-COL.
Besides the duplexed BP, many smokeless powders are excellent in the .458 Winchester Magnum. About anything between the burn rates of H4895 and AA-5744 will find a job to do. The SAAMI .458 WM at 3.340" and 60,000 psi will do it all from a 24" barrel: 600-grainer at 2000 fps 550-grainer at 2100 fps 500-grainer at 2200 fps 450-grainer at 2300 fps 400-grainer at 2400 fps 350-grainer at 2600 fps 300-grainer at 2800 fps (vaporization velocity of Sierra Pro Hunter, so use a monometal for sure at or above this velocity) 250 grainer at 3000 fps
The only thing of consequence that the .458 Lott can do any better is birdshot loads for a rat killin'.
Ron aka "Rip" for Riflecrank Internationale Permanente NRA Life Benefactor and Beneficiary .458 Winchester Magnum, Magnanimous in Victory THE WALKING DEAD does so remind me of Democrap voters. Donkeypox.
