If I were going to coat a gun rather than rebluing, I would use Brownells GunKote. It is a bake-on epoxy with molybdenum disulfide (moly) in it, and if properly applied, it is nearly impossible to remove. It comes in a variety of colors to match your needs or desires.
http://www.brownells.com/aspx/ns/sto...20GUN%20FINISH
Brownells also has another product that is similar, but has both PTFE and moly in it.
http://www.brownells.com/aspx/ns/sto...20GUN%20FINISH
Either looks very good when applied properly, and will protect the gun from scratches and rust. I refinished a gun years ago that had Brownells bake-on finish on it, and I had to sandblast it to get it off.
That said, I prefer the look of bluing. But bluing rusts and wears off eventually.