Conversion of velocity and foot pounds of energy...HELP

[Southern Shooter]

I have been looking at picking up some PRVI PARTIZAN ammunition for my .357 revolver. The specs for the particular ammo are as follows:

357 Magnum SJHP 158(gr) / 490(m/s) (1607 f/s) / 1225(J) (903 foot lbs) / 254mm (10 inches)

What would these numbers translate to for a 4" barrel of an average .357 magnum revolver instead of a 10" barrel like they used? Is there a formula I can use?

I have a 2.75" Ruger Speed-six revolver. I am trying to see what this ammo would do out that barrel.

Thanks

 

[Pistol Toter]

Projectile weight in grains X Velocity in fps divided by 1000 = foot pounds is the accepted formula and should be close from a 6" barrel. To determine what it will be form a shorter barrel; the rule of thumb will be a reduction of 50 to 100 fps per inch of barrel or approx 162fps to 325 fps less. The variation is attributal to factor of a particular gun, none are exactly alike. If your working on self defense, I doubt the perp could tell any difference.

 

[rbmcmjr]

What would these numbers translate to for a 4" barrel of an average .357 magnum revolver instead of a 10" barrel like they used? Is there a formula I can use?

There is no magic formula. All you can really do is compare loads from the same test barrel and make an educated guess. If you really need to know, you will have to get a chronograph and start experimenting.

Rick

 

[Pistol Toter]

If you really need to know, you will have to get a chronograph and start experimenting.

Essentially, that is correct. The formulas I quoted are ballpark.

 

[Guitargod1985]

I always heard it was (WxVxV) / 454500 = ft lbs. Where W=grains V=fps. I may be wrong though.