Formula for calculating FPS in longer barrel's?

[GSPBirdDog]

I am trying to find the formula used to figure out how many FPS (feet per second) every inch of a barrel gives you? Say if i went from a 5" pistol barrel to a 16" rifle barrel? I don't have a chronograph yet

 

[Litlratt]

All else being the same, the rule of thumb is 25 fps/inch.
However, that is for rifle powders. Fast burn rate pistol powders probably won't give you the same results.

 

[l c gun guy]

Think I herd some where that it like 25 or 30 fps per inch or so I wood get a crony tho they don't cost much and wood give you more accuarat data.

 

[GSPBirdDog]

Thanks guys! I called technical support at hodgon and he told me with 9mm i would get an extra 100-200 fps....I will just have to order a chrony and get back with ya! Thanks again!

 

[steve666]

The work already done for some calibers

Check out this site - Ballistics by the inch

 

[IndyBeerman]

Check out this site - Ballistics by the inch

Great link, repped for it!

 

[GSPBirdDog]

Check out this site - Ballistics by the inch

Damn good link and the tech at hodgon powder company was pretty much right on when i called them! Thanks again!