Welcome to Librarium Online!
this might be a dumb question but when choosing the railgun for the hammerhead gunship is it allowed to choose the different ammunition types on the fly or does 1 have to be chosen for the entire game?
You can use whichever one you want when you want. The only thing you *ought* to do though is tell your opponent which type of shot you're using when you fire the weapon, although picking up the large blast marker and placing it over one of his units is a bit of a giveaway!
"Tau Commandment #226: Participants who use Velocity Trackers in the Tau Clay Pigeon Tournament will be disqualified"