« Reply #7 on: October 28, 2012, 12:22:55 PM »
northkid,
A 45-120 has a lot more case capacity than a 458 WM, but the winchester round is a magnum meant to handle higher chamber pressure. You can launch bullets at or near 458WM velocities with the 45-120 but at lower chamber pressures and at the expensive of a lot more powder. If all you do is ream your BC to 45-120 and no other modifications I am fairly certain you will stop way short of 458WM velocity. IF you don't plan to modify your BC to handle more recoil (add weight, recoil pads, different stock set etc.) then just do as gcrank1 has suggested and I think you will forget about trying to copycat a 458WM. FWIW, I have launched many hundred very hot 45-120 loads from my gun, modified to weigh about 11 pounds, and I happy to say that i lived through it and have now moved on to loads that are a touch less insane.
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