I was stuck with 315lbs for 6 months, where I could only managed 7 reps alone, until I met this guy at my gym who told me to work on my back and triceps more. He showed me some very good execises, and one of them was weighted Dips. I did weighted dips twice weekly, and other varieties for triceps, and I was doing lots of rows. a year and half later, I owned the 405lbs without a scratch. It's all about the weak points.