I shoot a Winchester 94 in .44 Mag. I have killed a lot of deer (+/- 18) with this combo and 240 grain WWB's in the last several years. I have a Leupold 4x scope on it, and have killed from 8 to 90 yards. I would not hesitate to go with the Marlin and a 4x.
Well, after much agonizing, debating and seeking input from many (much thanks to everyone here!) I made a decision.............
Against pretty much all reason and rational argument I purchased a Rock River Arms .458 SOCOM! I added a Millet DMS scope and I love it!
So why this oddball cartridge in an expensive rifle platform (compared to some of the alternatives)? Several reasons:
I am an avid hand loader, so the lack of reasonably available factory ammo was not a big deal. I know that earlier I said that one thing I wanted was to be able to buy ammo easily if needed - but I got over that.. I realized that I have never lost my ammo in ~30 years of hunting, and if I loan it out the ammo goes with it.
I love hunting with and shooting my .45/70; the 458 SOCOM uses the same diameter bullets and I have found good loads using the same couple of powders in use in my .45/70.
It is a repeater! The rifle also uses standard AR15/M16 magazines so no high cost for special mags.
Ballistics are almost identical to the .45/70; a cartridge I have come to love hunting with and am familiar with the ballistics. I also have great confidence in the killing power of a well-placed .458 bullet at a MV of around 1900 fps.
Prior to this I had not owned an AR-type firearm, this gave me a reason to explore a whole different genre of hunting rifles. Some speculate that the acceptance of the AR platform as a hunting rifle may be a revolution in hunting arms similar to the acceptance of the bolt-action rifles (opinions do differ on this subject - time will tell)
The rifle/cartridge/optics combination is accurate. I have only shot at a maximum of 100 yds so far, but at that distance the accuracy is around an inch for 3 shots with the right load.
So, I again want to thank everyone who offered their experience and suggestions. I think that any one of a number of the options presented would have worked out fine. In the end, the versatility, power and overall "neat" factor won me over to the 458 SOCOM.