I'm leaning towards giving Gun Broker a try.
I've only recently bought a pistol there but have never sold anything.
List it as an auction with a reserve & see if it sells.
The fees seem reasonable. Any 'gotchas' I need to watch for in general?
As a GB user (buying and selling) for about 10 years, I'd recommend DO NOT put a reserve on it. That's a sure-fire way to have about 80% of potential buyers just ignore the auction.
And above all, post PLENTY of GOOD, CLEAR photos (at least 10 - 12, more is better) so that the buyer can be confident that they know what they're getting. If you can't post good photos, expect low bids.
The way to get the most money for something on GB is to list it at $.01 start, run the auction for about 2 weeks, and IME, end it on a Sunday night at about 10:30 PM Eastern time. If you don't have the guts to start it at a penny, then start it at a price that would be an excellent deal for a buyer of that gun. You have to somehow get people to start watching the auction, then over the course of the auction a couple of them will likely start wanting it and find themselves bidding it up right at the end.
But starting it at a penny will get the most potential buyers engaged, and will result in the gun bringing the most it's likely to bring. It might not be as much as you want for it, but it'll likely be the most it's "worth." I've sold quite a few guns like this and they always brought at the very top of the range for whatever the gun is, and I've watched hundreds of other auctions and seen the same thing. There are several GB sellers such as Lock Stock & Barrel and others who follow the "penny start and plenty of GOOD photos," and if you'll check you'll see that their auctions almost always do very well.
GB fees for a seller are reasonable. Fees for buyers have gotten pretty rough over the past couple years.