Esox,
One of the oldest myths in ballistics is that a "magnum" with a barrel shorter than 24" only gets "standard" cartridge velocities. Instead, the bigger cartridge will always push bullets faster.
In one experiment I shortened the barrel on a .300 Winchester Magnum to 22". It still got 3000+ fps with 180-grain bullets using published data. That's more than any 22-inch barreled .30-06 or .308 will get.
