You can do an amazing finish with Rust Brown. Done right its gorgeous. I've browned handcuffs, belt buckles, and a couple of really old 22 rifles.
It's more durable then blue and the more you handle it. The better it looks. It'll get a decent patina fairly quick. Deeper finish type thing. You can also apply it, polish with steel wool, clean it sterile, reapply, repeat. As many times as you want.
This is what I've always used. Good stuff. Easy to do and a heat gun helps.
Yea Ive played with Birchwood/Casey and did my granpa's ole Stevens .22 with it but my Dad had a Belgium Browning Auto .22 and 30-06 that need refinishing. Those are really important to me.
I'm sure you're aware that this model (I've owned a couple over the last 40 years) has an aluminum frame and steel cylinder/barrel. I'm not sure what finish will work equally on both types of metal. When I cold blued my old S&W 439 I had to use two different types of Casey's products because the frame was aluminum alloy. In the end I was pleased with the results but it was two-toned, just one darker than the other. Unfortunately the 439 suffered a cracked framed along the way and had to be destroyed for safety reasons. Good luck with any method you choose.