Welcome to the forums, I beleive
this article will help you best in answering that question.
My basic understanding of this information is that just because you eat a lot more doesn't mean your body can actually synthesize and build more muscle, as you add calories, you will build more muscle to a point and then the increase will plateau.
The studies cited imply that at most you can expect to gain .5lbs of dry muscle mass per week. In 6mo you have 24 weeks, so, at most you can gain 12lbs of actual muscle, and that is not including cutting time to reduce extra weight from building the muscle. I don't think 30lb's sounds like a reasonable goal, but actual dry muscle is more powerful than people give it credit for, and with good training and gaining muscle, I wouldn't be surprised if you outperformed the other guys, even if you are lighter in muscle.
However, gaining 30lbs in general can be done in 6mo.