Check out this shotgun I just scored!

That's not something you own IMO.
If he is truly your friend, then you should have it in your head that you don't own that shotgun, instead you are simply storing it for him until the day comes that..
1. He comes to his senses, and realizes that it's not just a "gun" it's a family heirloom, and a rather valuable and irreplaceable one, and put's his foot down with his wife
2. His wife overcomes the lame "feels" that a scary gun causes her.
3. His son/daughter reaches the age to appreciate it a little bit more than dad's clueless self does, and it can be gifted back into the family.
Some people are saying it's a nice "score", but to me it's taking advantage of a friend, but again that's just my opinion