Wasn't it Brister who said a 12ga load started at 1330fps and a load started at 1200fps would have the same velocity at 45yards? Just bought a box of Winchester SuperX that had velocity and not Dram Eq. on the box.(item x12p5)
That theory can be proven with a simple balloon. Wind up and throw it as hard as you can, and then gently lob it in the same direction. The hard/fast tossed one decelerates faster than the gently lobbed one, both ending up at about the same spot in about the same amount of elapsed time. Air resistance acting on a round object in flight is a b*tch. The faster it goes, the faster it slows down. One more reason to question the use of high velocity magnum shotgun cartridges. (Increased amount of shot payload is one argument, but that's a moot point too if the gun patterns lesser weight charges nicely. Do we really need 15-18 pellet strikes on a bird versus 10 or 12?)
Interesting about those SuperX box markings. Perhaps the "Times they are a changin'". I haven't bought a box of factory shotshells in years, so wouldn't have noticed it.
