I don't really see the advantage in a purpose built 45/70 semi (that is unless you want something unusual, which I sometimes do) when the 458 SOCOM already mirrors the 45/70. The Bushmaster 450 that some have mentioned doesn't actually equate to a 45/70 though that was a sort of selling point when the thumper released. The 450 does have a slight advantage velocity/trajectory over a 45/70 wise but doesn't have the bullet weights that are available in either the 458 or 45/70 something up to 600 grains or some such. 405 grain hardcasts are enough for my shoulder.