Since light-for-caliber bullets are being discussed for the GREAT .458 Win, I've gone on record as liking the 300 TSX. It's accurate and fast from my Ruger No.1, whether at about 2750 fps or +2900 fps. The advantage of the 300 with the poly tip is expansion as low as 1400 fps (I read that somewhere).
But here's another point of interest which I made mention of in 2011 in the second edition of my manual on the .458: According to NRA's HANDLOADING book circa 1981, "The WORKING chamber pressure for the .458 Winchester Magnum is COMMONLY limited to ABOUT 53,000 c.u.p. The established MAXIMUM product AVERAGE for FACTORY ammunition is 56,200 c.u.p." Highlights are mine.
Whether we multiply CUP by 1.18x for PSI (As per Accurate powder) or 1.13x , that would make a "within reasonable" maximum psi to be anywhere from 63,500 to 66, 200 psi - and max reloads from manuals are often far less than even 53,000 cup. Check the Winchester data as per Hodgdon at around 43, 000 to 44,000 cup.at factory levels of about 2040 - 2065 fps for the 500 - 510gr. So, I have few qualms over loading the .458 to any psi that appears safe based on common visual and physical effects on the brass and ejection. It's very difficult to overload the GREAT .458 with suitable powders -- that's one advantage of the relatively short case.
As someone pointed out a long time ago re the single-shot Ruger in .45-70: "You'll reach a point in recoil that limits your choice of loads long before you reach the limit of the Ruger's true capability". In a similar way, that equally applies to the wonderful .458 Winchester Magnum.
