The skinnies poach elephants with AK47's. Every one of the rifles you listed ONLY shoot the lower powered service rifle ammo. You can't shoot a box of quality 308 rem through them. They pop the primers and jam the gun. I had the SCAR 20 what a heavy ***. I sold it two months later at a big loss. A real full 55,000+ psi AR10 is what you wantI was thinking about a 308 semi-auto rifle that can hold at least 20+ rounds like the AK M77, Scar 17 or HK G3/PTR style rifles where you can fire off more rounds quicker than a bolt action or Marlin lever gun.
If I was really worried about bear attacks simply packing a big pistol is all you need. But on our Alaskan bear hunts I always took my 458 win mag or my 458 Barnes American. Always one shot kills even the 9'6" brown. My hand loaded 510 gr RSP hit it in the chest walk towards us and blew out its butt cheek. DRT. Some of the locals just use their .270's for everything.