Very low reps (1-4) at a high resistance (85-100% of a 1-rep max) is the standard powerlifter workout. But usually you'd do that for many sets. Lifting a 1RM for a single set seems either grossly inefficient (I have a similar max and it takes me 6 warmup sets just to get into the 405+ range), or he's risking injury by not warming up enough.