If you are looking for GOOD adhesion and durability, you really want to consider getting it sand blasted (not bead blasted).    Preheat the barrel, and coat it with whatever you decide.  If you are looking at krylon, just remember that it is a basic spray paint, which is fine if you understand its limitations.

Ceramic header paint from Duplicolor (600 or 1200 degree) works much better, and is solvent resistant.  If you follow the instructions on the cam, you will have good results.  Its not Norrells, but it works much better than a basic spray paint.