The SAAMI .458 WM throat allows use of .461-caliber cast bullets loaded long. I am convinced that, combined with PC paint, gas check and hard alloy, the .461" diameter is best in the common .459"-grooved .458 WM, for top accuracy and velocity smokeless loads. A .459"-diameter parallel-sided free-bore of whatever length requires fussing with bore-rider noses and other delicacies. Consider the poor ol' .458 Lott. The no-throat .45-70 Govt. might be better with paper-patched bullets, or we just have to get fussy and patch our full-bore slicks to groove diameter in a .458 WM or .458 WM+ or .45-2.6" SWT.
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.