How about the Brenneke slugs, but with a fast firing Benelli M4?
It's a polar bear. Can't really think of anything more frightening, unless a T-rex appears.
I have built some shotguns for Puddle Jumper Pilots in AK and they opted for smooth bore 18.5" with tritium rifle sights or a tritium bead.
You don't want a slug that deforms on impact (like many are designed to do), when you need SERIOUS penetration to include breaking through multiple inches of thick cranial plate.
Again...that is a very nice and EXPENSIVE gun. For a 6 month stint...the OP may not be wanting to spend that kind of money.Google "Alaskan Co Pilot" or "Wild West Guns". They have taken a 45-70 Marlin into the next level. Gun disassembles into small pack and reassembles quickly. I have seen it used on charging Brown bear and it is almost unbelievable.
blindhari
If I'm not mistaken most with exception of one line are inertia operated which is fancy word for coil spring operated system. They once made one that was dual pump/semi mode but the pump mode was found to be superfluous.I know the Benelli has been mentioned as an alternative to a pump action shotgun. Are their any issues / disadvantages with a gas operated semiauto shooting slugs in a cold climate?
I haven't handled too many myself to have an opinion on them.
The penetration would be more then adequate if you find hard lead non-deforming ones from early 70s that marketed by Smith & Wesson though some in five pack might be past best if used by date. Not what I would want packing in magazine when in bear country.