I've only heard the bullet hit once. Took a doe at 40 yards with a muzzleloader. I was shooting a 460gr Hornady Great Plains conical with 90gr pyrodex that might have just been a little over supersonic at the muzzle, but I don't really know how fast it was going. I definately heard the hollow thump when the bullet hit her, followed shortly by a second thud of her hitting the ground less than 6 feet from where I shot her.

Never seen a vapor trail, but I've seen the bullets from a 45acp and the pattern from turkey loads in flight out to about 25 yards.

Mike