Yes, it will work on barrels, but you have to keep your solvents off the painted surfaces when cleaning your guns, or your paint wont last long.
I've used Krylon on both stocks and metals, and have cleaned it off both without much hassle. bowflage is less of a headache on barrelled actions IMHO, but doesnt last as long as krylon unless you clearcoat it. But than again, neither do the seasons out here in Ontario, so I have been painting my guns every 3-4 months anyways...
Make sure you use a good thinner to clean all of the surfaces first, and your good to go.
We had a couple threads going over in the hunting section about painting guns in the last while...