A formula for all? I don't think so....
Go to Buffalo Bore's site and look at their results. They list the velocities for each load with different barrel lengths.
At first, their 125 gr .357 stuff goes slightly faster with a barrel length increase but then peaks and actually slows down as the barrel gets longer and longer while their 158 gr loads just go faster as the barrels get longer.
It's not only the gun's barrel length that determines velocity but also the characteristics of the powder used. Buffalo Bore's 125 gr stuff must burn really quickly or something because it seems to have run out out of steam before exiting the longest barrels.
In order to make up a formula, one would have to quantify the expansion & burn rate of each bullet with each individual powder or powder combination. I guess one could come up with a formula for a load, a unique one for that load only, but it'd be difficult. The formula would be good for that specific loading only.
Go to Buffalo Bore's site and look at their results. They list the velocities for each load with different barrel lengths.
At first, their 125 gr .357 stuff goes slightly faster with a barrel length increase but then peaks and actually slows down as the barrel gets longer and longer while their 158 gr loads just go faster as the barrels get longer.
It's not only the gun's barrel length that determines velocity but also the characteristics of the powder used. Buffalo Bore's 125 gr stuff must burn really quickly or something because it seems to have run out out of steam before exiting the longest barrels.
In order to make up a formula, one would have to quantify the expansion & burn rate of each bullet with each individual powder or powder combination. I guess one could come up with a formula for a load, a unique one for that load only, but it'd be difficult. The formula would be good for that specific loading only.