Low rep ranges definately build mas but MASS building takes a lot longer then 9 months it takes years especially if you're not on gear, and I agree w/ contraction that there's a lot more to it. Another thing is you cant do every thing you do in any one rep range forever you can do 6-8 reps for awhile then youre going to have to do something different.
As was previously stated, mass building depends on more than one factor.Personally, I experiernce the best size gains when using a rep range of 4-6 reps.Someone fairly new to training will probably need to use a slightly higher rep range.Maybe 8-10.It's an individual thing.
I prefer 6-8 right now, of course I'm to new to the game to figure out which works best for me. Only thing I can tell is this gives me the most consistant improvments as far as being able do squeeze out an additional rep next time I work that part