This kind of test was first done and published over 50 years ago, and seems to get re-done every five years or so by some gun magazine with empty space to fill. Still, several myths remain even though the tests consistently show that:
- the powder that gives the highest MV with a long barrel will give the highest MV with a short barrel; and
- while larger cartridges lose the most MV per inch reduction in barrel length, they are always faster than the smaller cartridge. In other words, a 16" barrel does not turn a 300 Win Mag into a 308 - it will be considerably faster than a 16" barrelled 308.
If someone wants a 16" barreled 30 cal capable of firing a 190gr bullet at 2500 fps+, you need a 300 Win Mag or larger.