Are you looking at this from reverrse? Velocity as a function of the barrel length?
No chrony, unfortunately.
I guess I should buy a chrony.
Cutting the barrel shorter an inch at a time provides much more useful data. Especially if you keep going down all the way to the breech block.
On most of the others, I went 1" or less at a time. But not for the velocity; I was interested in the accuracy.
And I pulled the Plink constant because of Jim-in-UK's post about the HW80 being at least not too long, if anything. Although who knows what velocity/pellet that was with.
Thanks JimTaking your velocity data and assuming it is for a 15 grain .22 pellet;I get 12 FPE at 16" of pellet travel, and 9.7 FPE at 8".From the energy acquired in the first and second 8" increments, I calculated the average pressures (above that to overcome friction) for those two segments; based on the pellet base area, creating an average force to equate to the FPE increments.The chart below shows the average pressures for the two 8" segments; with a hand drawn red line trying to approximate the actual pressure curve. The idea is to have the same average areas under the curve as the average pressure curves. I did not do a good job of drawing the red line because I am using a mouse curser to do it, and my hand stubbornly refuses to move smoothly. It would be better to generate a regression curve, but my scribble should be enough to make my point: The air pressure curve for a springer is very non-linear. Thus barrel length to velocity calculations need to follow a curve that sees the fast decaying pressure adding reducing incremental FPE per inch; based on the average air pressure acting along that inch of barrel. From that, calculating the velocity should be easy enough.In the example given, cutting the 16" barrel down to 8" may only cost 10% velocity, but there is a risk that the higher muzzle pressure may start to buffet the pellet at muzzle exit - not good for grouping. Then again, muzzle pressure from FAC PCPs is much higher; but they almost always incorporate an air stripper to reduce its effects.