Barrel Lenght v. Velocity +/-

[SDJim]

I'm looking for an online calculator (or other reference) to determine the relative increase / decrease of muzzle velocity corresponding to changing barrel lengths.

I want to install a new barrel on my target rifle to shoot Palma. The rifle currently has a 24" barrel and for the sake of argument SMK's are leaving the barrel @ 2650 fps. I'd like to see what the new estimated velocity would be with the same loads with a 26 - 30" barrel.

The best I've been able to figure out is that there is a 5 - 25 fps increase for every additional inch of barrel length.

I was hoping to get something a little bit better than a 25 - 150 fps SWAG.

Thanks

[pc_city]

This site has a table comparing velocity vs barrel lenghth.
http://www.6mmbr.com/308Win.html

[Fjold]

The problem is that each barrel is different. Some barrels are faster than others and the rate of change in velocity per unit of length change is different.

If you use different powders then the rate of change will vary also.

The rate of change is different for different starting lengths also. For example adding one inch to a 16" barrel will vary the velocity much differently than adding an inch to a 24" barrel.

[rksimple]

Like Frank said, lots of variables. Something as simple as changing powders from your current load could yield much greater or not-so-stellar gains in velocity. You just need to try it. However, the gain from 24" to 26" should be negligible. You'd probably need to go to 28"-30" to make it worthwhile over your current setup.

[SDJim]

This site has a table comparing velocity vs barrel lenghth.
http://www.6mmbr.com/308Win.html
For as often as I hangout on that site, I don't know why I never saw that table before, and the one below that talks about twist rates will help answer another question.

Thanks Much. SDJim