Need some tips on Gangplank.

I just played some gp mid and i did fine. I got a good ulti on bot lane early in, and our jungler ganked the enemy heim once, so i was pretty well off. Once we started teamfighting, however, we couldn't win a single fight. Most of the time, i couldn't land a single barrel on anyone. I'd have good placement, but the enemy team would just run right out of it. Was it because we didn't have any cc? Morgana support was our only CC other than rek sai knock up. Meanwhile the enemy team had an amumu and a malzahar and an udyr who opened d gates at bot lane so well he almost got 2 nexus turrets before the 20 min mark. Am i supposed to be placing 2 barrels, blowing one up, then placing a third barrel in range of the second?