Is there a way to calculate velocity of a shorter barrel if velocity of a longer barrel is known?In rifles my experience has been roughly 50fps per inch.Anyone got any ideas for pistols?

There are exceptions to every rule. But here are some to go by. After 14-15in you can pretty much bet on, from my experiences, 33fps per inch. In-between 10-14 you can usually bank on 150-200 fps. Some exceptions will include smaller calibers shooting light bullets. They will generally loose 400 fps from rifle to pistol, EG the 22-250. Big bores shooting larger heavier projectiles will loose less. A 44 Mag looses +/-50 fps shooting a 300gr bullet when comparing 10 and 14 in barrels. Long story short, you can usually say 300fps from rifle to 14in shortgun.

Duane

Yep, that's pretty much how it works. Big bores don't suffer as much as smaller bores. The difference is greater exponentially as the steel gets shorter. There is no way to calculate what it will be, you gotta shoot 'em over a chrony. What cartridge are you thinking about?

44mag calculations from 7 1/2,8 3/8 to 5 1/2".Most data will give you what should be out of the longer 2 barrels and i was wanting to figure what could be from a 5 1/2".I know reloading data fps are not always achieved and some times over achieved but it will get me in the same ballpark.

In my experience, with handguns anyway, its usually roughly 50 fps or somewhere close to that value.

Most revolver data is tested in either 5-1/2" or 7-1/2" barrels, not so much in 8-3/8" and over. There is not going to be a whole lotta variance, not enough to make a difference on a critter anyway.

The loss is different with different powders because of the different burn rates too.