To my knowledge, it's usually recommended to do higher rep ranges for squats to build mass. For bulking, I stick to 6-12 rep ranges for all exercises except for squats I stick to the 8-15 rep range. In fact, one of the best programs for developing muscle mass is known as the "20-rep squat program" (look it up) and it recommends doing one set for squats, 3 times a week, with moderate weight for at least 20 reps or to failure. I've tried this once and it did give me great results with the right diet. I think doing squats for 50 reps would force you to use very light weight and I can't see this being as effective at developing mass as lower rep ranges (6-20 reps).