you'll need a cutter of choice (11°, flat/recessed, etc.) and an arbor/pilot bushing matched to your bore diameter.

these are sold at midway and brownells, among others.

for purposes of exact concentricity, it is best crowned in a lathe, but guys have used various power tools ranging from cordless drills and drill presses to die grinders and wooden stands.

the keys to a good crown job are locating the cutting tool parallel and concentric to the bore axis and fixturing that is solid enough to prevent tool chatter/movement.