Yeah you pick Y to switch guns, but one thing I noticed though if you keep hitting Y it will put you back on the ground and you have to hit the dpad again to go back up into the C130. Or at least it did that to me last night. And I couldn't hit the broad side of a barn with anything but the howitzer.
Yeah I noticed that, so I started leading them, and the impacts were within the little red boxes and I didn't receive any points. So I just stuck to the Howitzer. Pretty much a guaranteed kill every shot. It just takes forever to reload. LOL