Manitou, if I had a SAFE, secure place for a 'spare' gun, like you describe, I'd certainly bring one.
Not sure about your insurance, but mine has a deductible. Crash the car? I'm out the first $1000. With the guns, I'm out the first $500. That's a painful loss to 'eat' so someone else can enjoy my stuff.
I'm a fan of the "spare rifle" concept. I just question the execution. No gunsmith around? You can buy a gun and scope at the local town, along with ammo, then sight in on a tree stump out in the woods and be back in action. Get back home and sell it and only be out $100 or so.
It's those hunts were you are well and deep into "nowhere" when a second rifle makes sense. But packing in that additional 8 to 10 lbs and 36in to 46in of length gets tricky. Maybe that's when a 'spare' .44 Mag revolver with a red dot on it comes into play? Now you are limited to 100yards or so, but you HAVE a back-up. And you can pack it in on your hip or in a chest rig. Probably won't be great for a sheep hunt though, ha! There is no "easy" plan. All have risks or problems.
Thinking of the old Road Runner cartoons and ACME stuff - perhaps pack in a dehydrated gun, where you just add water. Perfect.
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