Bobster
.30-06
Under warning it says: "Never shoot slugs with a full choke. Use only the most open (improved cylinder) choke. Never shoot steel shot with a full choke. Use only a modified, improved cylinder or skeet choke tubes."
The key word here is "choke" and cylinder bore means no choke. The bore is the same size the length of the barrel. The choke is a restriction, or decreased diameter of the muzzle end of the barrel. Do a search here at MO on "choke tube" or similar--there is tons of info about the subject and choke sizes.