One of the things Leatham taught us was that shooting really long fast groups will teach you a lot about the natural rhythym of the gun and your trigger pulls. He suggested 15-20 round groups at as close as 7 yards. Of course his were still one hole, but yours should be pretty good too. One thing you should notice is that your splits (the time between shots) get faster as you go. That's because you are learning how much you have to release the trigger to get it to reset. You will naturally start keeping more and more pressure on the trigger throughout the cycle.
An important thing to remember is that a firm grip is important and necessary to do this well.
Seems like a waste of ammo, but if Leatham says to do it, it must make sense. Try it and you'll know it does.