Re: 45-70 Gov. VS .338 MAG VS .300 Mag.
If we didn't find the post interesting we would not have read it. But you have to admit 45/70 and long range is an oxymoron. That's what struck me as so funny! And I own a 45/70!
The OP has a valid question, but which would you choose? I go for all - around first and choose something more specialized second or even third. As such the 338 WinMag is my recommendation. But if you hunt primarily in very close quarters, and I did that very thing for two decades, the choice would be the 45/70. That is what has been my primary elk gun since 1976. I just haven't had the opportunity to hunt at longer ranges, until now. BTW Ruger #3 in 45/70 is my most favorite gun in the safe hands down. Everybody needs one IMO.
The 300 WinMag is a very good choice as an all around gun. Gophers to Moose. Not a first choice for either. My youngest son's first big game rifle is in 300 WinMag because I believe it is the best all around caliber choice today. Bar none!
Do I own a 338 WinMag? No. Because last year when I made this very same decision I chose a 375 Ruger chambered in a Savage Weather Warrior. Added a Factory installed 26" tube too. But he asked about a 338 and since I personally came within a gnat's hair of buying that very caliber, of course I'm going to recommend it. Same parameters I considered when starting my search.
But a 45/70 discussed on a Long Range Website? That's funny I don't care who you are....
P.S. The OP's three caliber choices are THE three calibers I would recommend for a three gun battery. Perfect choice to cover it all. My real advice? Get all three!