 Mag., like many magnum rounds, can wear out barrel throats more rapidly than lower pressure and lower velocity non-magnum cartridges, especially when fired rapidly, which heats up the steel and hastens throat erosion.Throat erosion is greater in higher chamber pressure overbore cartridges.This was particularly true in the 1950s to early 1960s, with the chrome moly steels almost universally used for barrels then.