Forget the Marine stuff, and let's get on with the matter at hand. The Win. 100 has a following. I have no experIence with them, only the sister model 88. Those were way over engineered IMHO.
The .270 is a fine round.i have two, but I also have a trio of .30-06s, so they would be favored for an elk or larger. But, if you are looking for an all round caliber, the .280 might be a better all round choice, although it will not quite reach the velocity of the 7 magnum. The other advantage is a bit lighter, handier package. My suggestion would be to forget the muzzle brake. You just do not need it on the .280 and it will increase the noise level. There are lots of fine loading s available, and hand loading would open up even more options.
Thanks for your service. Enjoy the Ruger. Jack