I have found that you cant generalise and say it will increase velocity, it probably will but it depends on other factors too, if the firing valve is still open when the pellet leaves the barrel then yes it will increase the velocity. But if the valve is closed before the pellet left the original shorter barrel then a longer barrel can lower the velocity. I have seen velocities go up when reducing 19" pcp barrels to 16".
HFT, for people with only 2 buttucks!
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