.500 Velocity Loss vs Barrel Length?

[off road]

Most manufacturers quote velocities obtained from rather long barrels. For example Hornady 350 grain XTP, it quotes 1700 fps/2246 ft-lbs from an 8.5" barrel. http://www.hornady.com/store/500-SW-350-gr-XTP-Mag/

What velocity loss would one expect with a 4" barrel. (I realize that this is actually a 3" barrel, with 1" of compensator.) Guestimates are welcome, but would really appreciate some chronographed emperical data if it is out there! Thanks!

[OKFC05]

You got it right when you said you need chrono data.
Rules of thumb are approximate at best.
The type of powder drastically affects the % of vel loss in shorter barrels.

[off road]

Finally perhaps ready to make a purchase. Intended use is bear defense: Product: Model S&W500

Bumping this hoping for a response. I have searched around, and found hearsay estimates like you should expect a 25% velocity loss (vs 8.38"), but found no actual chrono data.

My deilema is that I already have a .454 Ruger SRH (7.5" barrel). It seems that a 4" .500 will get knocked back to aprox. the level of the longer barreled .454.....so I have to wonder if it is worth the money to get the .500 or just live with the big Ruger. Actually, the Ruger is a few ounces lighter, but also ~3" longer. The big Ruger is clumsy to draw in an emergency, but the X-frame is a beast as well.

[jlanecole]

I'd keep the Ruger and never look back. For bears, I just can't see that much difference. If you want to buy a new gun, well I understand that, too.

[off road]

I already have the Ruger Alaskans, but again we are dealing with velocity loss from the short barrels. The .44 really suffers and gets knocked back to the energy levels of a .357 fired from a long barrel. The .454 fares much better from a short barrel. Even from the 2.5", it is still considerably better than a .44 fired from a long barrel.