Velocity Q

[C-son]

I have a .22 velocity question.
Let's say a typical .22 bullet has 330 m/s muzzle velocity in a regular 660 mm barrel. Is there a way to calculate (or transform) this velocity for a longer barrel, like my 690 mm? I don't have access to a chronograph. Thankful for help.

[Gort]

There is no accuate formula, there are too many variables. That being said, as a general rule, most rimfire .22 reach a maximum velocity in about 400mm of barrel. The expantion ratio of such a small straitwall case will not allow it. Velocity should peak at about 400mm, level off out to maybe 500mm and slowly decline after that. To summize the differance between 660mm and 690mm is probably less than the standard deviation of the cartidge. In otherwords, ignore it.
Gort

[C-son]

I see, thank you very much!