Forebore - agree the only difference between the 458 American and the 450 Marlin is the band width and position on the case. The point I was trying to make is that a manufacture (Hornady) commercially produced the 450 Marlin and I don't think anyone ever commercially produced the 458 American. Maybe IF someone had, the 458 American would have become commercially viable. But then too, the manufacturer would have very likely run into the liability issues of a few idiots trying to interchange American and Win Mag. Just like you "CAN" shoot Win Mag in a Lott chambered rifle, most don't recommend a steady diet of it as it can mess up the chamber over time. So, you end up back for the reasons for the 450 Marlin - greater performance while hopefully reducing liability.
I believe the fear was firing a 458 American in something like a 357H&H or any smaller bore belted magnum. That would be interesting! Too bad, I liked the concept. And as far as I can tell the 350 rem mag had the same issue and no problem. Maybe an older time.
I could not resist a little jab against the 450.
I do see your point, had a factory loaded 450 been available, who knows.
