If you're gonna apol;ogize for swearing don't do it.
also, when an ordnance blast can't miss, then you are screwed.If you're worried abput ;osing a few marines, then when all your trukks go down turn one, then you are screwed.When a hail of bolters/ pulse weapons decimate your forces you are screwed. Switching from the toughest basic troops to one of the weakest is not the best choice in the world if you play only to win, as you will lose your first games, but from what I undertstand about you that isn't a problem, so I congragulate on your change.
BTW, what SM chapter do you play?