My wife is a surgical PA. She started with a total knee/total hip replacement surgeon. He's ranked as one of the best in the nation.
Now she's with a surgeon that does nothing but hands. He is similarly highly ranked.
I can't give you any anecdotes from experience, but here's one thing I've learned.
What do you call the guy who graduated last in his class at med school?
"Doctor."
Just because someone is a doctor, doesn't mean they're any good. Some of the stories she tells, scare me enough to really, really, dread surgery.
All I can tell you is that before your relative consents to any kind of surgery, ask around about how good he is. Go to the hospital where he operates and ask the personnel re the doc's reputation. Yes, the doc is prohibited from sharing case histories, but staff are amazingly blunt about his success rate.
Was he fellowship trained?
Go to a physical therapy facility in your area. Ask them about the surgeon.
You can even go online and find out if he has any outstanding lawsuits against him.
It's very important to check his reputation.
Best of luck to your BIL.
Edited to add: I asked my wife re the situation. The surgeon she works for won't even do wrist replacement. Fusion can allow the OP's BIL to live pain free. But there are different types. One type will lock the wrist in a stationary position. From her description, it sounds like he might be able to resume shooting mild caliber hand guns and long guns.