I have to agree with RLewis on this. I've always heard that if you are doing a clean bulk, you really shouldn't expect more than 2-3 pounds of REAL muscle a month. On top of diet and your routine, your body type and genetics play a big role in how much mass you will put on. It's always easiest in the beginning of a bulk stage to put on muscle, but after that first month, 2-3 pounds is a very very solid gain. It's a slow road, but doing it like that turns into 24-36 pounds a year...and that's a TON.