Waterfowler;
Do you hand load your ammo or rely on factory stuff?
What is your age and health condition?
Do you hunt with a "gang" or do it mostly solo?
Those, and other questions, are very important, including do you like variety or prefer what everyone else does?
It seems to me that in all the answers so-far, the trend is to choose from a limited spectrum of cartridges, i.e: .270, .308, .30-06, etc. As it has been mentioned, you already have a .270 so, to me, you have that group of cartridges covered... doing what "everyone" else does.
Why not try something else that's different? I've been hunting for about 60 yrs, and have used most big-game cartridges from .25-06 to .458 Win Mag, because I handload 'em. If you handload, you can turn a .300 Weatherby (or .300 WM or WSM) into anything from a .30-30 on up through .308 Win, .30-06, etc. But you can't turn a .308 Win into a .300 Winchester or Weatherby. You can also turn a 22" bolt-action .458 Win Mag into a 22" bolt-actiopn .45-70, and I've done it. I've also used them as .458 Win Mags in moose hunting... makes a great brush gun!
Use a little imagination! Nothing wrong with a Marlin .45-70 (I've owned a bunch), as long as you handload, and it would be perfect in the conditions you describe (Incidently, I hunt in those same areas, under the same conditions you describe. But, for several years I've hunted N. Ont. for moose and bl. bear. Because of the clear cuts, I tote something that will reach out to 400yds with ease and still deliver adequate punch, like a .338 Win Mag or .300 Win Mag).
You need to consider your options... will you ever hunt moose in the northern regions of Ontario. Not many, with experience, tote .308 Winchesters or .270s up there. If they have in the past, they switched to numbers like .300s and .338 magnums.
I've been hunting bear since the beginning of September. Had to put down a bear that a young friend crippled. The last couple of days I've been moose hunting with a bear tag and wolf tag in my pocket, up in the Haliburton Highlands. My partner was toting his 270 Winchester with Federal factory 150s and I a Tikka Lite in 9.3 X 62 with handloaded 286gr Hornadys. My rifle has a synthetic stock, a match grade Sako barrel that shoots less than MOA and weighs 2 lbs less than his while being 40% more "powerful" and making a bigger hole, which to me is important in bear hunting in particular.
Today, the 9.3 X 62 is coming on very strong in North America while it has always (since 1905) been THE cartridge in Europe for Red Stag, pigs and moose. In Africa it has been effectively used on everything, including elephant with solids. Hornady, Remington, Federal, Winchester, Norma, PRVI and S&B all produce factory ammo, as well as components, for it. EPPS carries both factory ammo and components for handloading. That's where I bought my rifle.
Ballistically, it's considered on a par with the .338 Win Mag, slightly less than a .375 H&H and slightly better than a .35 Whelen (and I've handloaded for all of those ,by the way). In my view, like a .45-70, it's the best of both worlds... it's perfect for anything from deer to brown bear in North America, and most African game as well. And, it burns a modest amount of powder (about the same as a .30-06), 15 grs LESS than a .338 Win Mag or .375 H&H... meaning it has about the recoil of a .300 Win Mag but is a LOT MORE effective using the right load.
In my view, after a lifetime of hunting, it's the PERFECT rig for all North American hunting! (9.3mm = .366-inch)
Think outside the box.
Bob
www.bigbores.ca
