Jay,
Maximum PBR combines a plus or minus bullet trajectory/path over the line of sight/aiming line. I often hear the plus/minus as plus/minus 3 inches. If you were utilizing a PBR concept, you would zero at a range the bullet trajectory would not travel above 3 inches line of aim, and at max PBR range the bullet would drop below 3 inches from the line of aim.
For example, I commonly zero a 30-06 with 180 Partitions, muzzle velocity roughly 2750, at 25 yards. With this aim point the bullet is 2.8 inches above the line of aim at 125 yards, and falls below 3 inches below the line of aim just before 275 yards. So my max PBR for this configuration is 275 yards. If I wanted to shoot a big game animal within 275 yards I would expect the bullet to hit vitals, as I would aim in the middle of the chest.
Clear as mud?
As for sectional density, it's just a comparison of a bullet's weight to its diameter. Many here, myself included, believe bullet construction and placement to be of more significance than sectional density. Others would argue increased sectional density improves penetration. Probably somewhere in between.
Ever read the Berger Reloading manual? It's has excellent articles before the load data.
v/r
Joel
