Feel free to read Mule Deer's extensive discussions about this. But in my personal experience, shortening and threading a bunch of different barrels for supressors--same barrel, same chamber, same ammo--
7WSM lost 38fps per inch cut (Win factory 150gr power points)
300 Win Mag lost 34 fps per inch (Fed factory 180 partitions)
338 Win mag lost 30 fps per inch (Fed factory 250 partitions)
It's not magic. 70 grains of powder burning in 20 inches of barrel makes the bullet go faster than 45 grains of powder burning in the same space.
Have you done this yourself and gotten different results? Or are you repeating something you read? Or do you not remember?
