Final Fantasy XIV Database - Ffxivpro.com

COR isn't exactly the best puller. Guns typically have ridiculously high delay, and outpulling another party in competition is out of the question, and quick draw has only 2 charges with a minute recast on each. But really COR should be puller as a last resort and with /nin sub only.

To really get full use out of your damage potential, sub ranger as often as you can. Another option at later levels is to sub white mage and wear full +MP gear to be 100% support based for cases where it would be futile to shoot something. However this really only applies to much higher level situations or manaburns.

Also if you really are going all out on COR, I strongly recommend you start leveling up alchemy to make your own bullets or find a friend who does. Otherwise it'll cost you an arm and a leg to prep up for a good long party.