Depending on where we hunt, at the end of the day. I personally rather train harder and hunt comfortably. If you are in the thick stuff rifle is in hand. Walking from spot to spot is different. Just depends.
Maybe I did not do a good job of explaining, that I do for elk hunting. When you pack in for a week it is a little weight. We are in flat land, so to offset that to the best of my abilities I load up the weight. It never hurt my to put some work in. It is better on my knees than running on top of that.
If someone wanted to train to carry a rifle, kettle bells would be just fine. It sounds like a lot, start light and work your way up. You will be surprised what you can accomplish. I'm not a crazy fit person, 6' - 190. When I was younger, I was the same weight just at 9% body fat. Hahaha not the case now.