I was doing some simulations today for a couple of .357 Magnum rifle loads, and I noticed something I had never seen before. It seems that when I decreased the amount of powder for the load, it moved the peak pressure point and powder burn out point closer to the muzzle (or after the bullet left the barrel), and when I increased the load, it moved the peak pressure point and powder burn out point closer to the breech. I tried it with a few different powders to see what the effect was, and in each case, it was the same.
Is this really the way it works, and if so, why?