Anyone have any software to recommend for calculating how muzzle velocity changes with barrel length?
I have Ballistic Basics which claims a uniform 50 fps reduction per inch, completely independent of initial length and velocity. Which I find hard to believe.

Kevral---

There are no definite rules about how much velocity is attained between rifles of the same caliber and barrel length......there's no way to calculate what any one rifle will lose.

50fps per inch is a lot. Usually only the overbore cartridges lose that much.

Guess I should have understood that.
Thanks, though!

I read an article once that stated 20fps loss per inch for a .30-06 from 26" down to 18". Charlie Sisk did the same test with several cartridges magnum and non-magnum, then reported it on the 24hr campfire website. He came up with the same results.

Quickload shows it very well:

Pick your barrel length, and it gives velocity, muzzle pressure in psi, percent powder burned at that muzzle length, and a whole bunch more things. Just iterate the barrel length and you come up with some interesting data, that is very near actual conditions as I have experienced in using Quickload along with the Oehler M43 pressure & velocity system. Plus Quickload will plot a curve of the barrel pressure along the length, very handy for those working with gas guns and needing to know the ideal location for the gas bleed port in the barrel: put the port too close to the receiver and you batter the action, put it too close to the muzzle and you have lazy operation.

Only bug in Quickload is as the case nears straight wall, like a 458 Win, the data calculations err to the conservative side.