You have not been brief for your specific role yet. that will come in the next post. As for wargear, ya shotguns are cool but I wouldn't worry about it too much. If you really want one you can adjust your CS now and it's no big deal, but boltguns are standard issue for a reason, They work in nearly any scenario and environment. I always think of space marine shotguns as clearing cramped space hulks & underground tunnel crawling but you do you.