Optimal bbl length for spring piston airgun?

[Futo Inu]

I need to know when the pellet quits accelerating and begins decelerating in a "magnum" .177 cal spring piston airgun. Specifically, I need to know for my RWS Model 350.

I ask because I know that .22lr hi-vel, for example, stops accelerating at around 12", maybe a little more, but definitely under 16", in a .22 firearm. And the RWS model 48/52/54 has more power with its 17" bbl than the 19"-bbl'ed Model 34 that I had. The 350 has more power yet, but since the 48/52 is plenty powerful at 17", I'm wondering if I wouldn't get even more power (or the same anyway), and a handier/lighter rifle if I cut my model 350's 19.5" bbl down to around 17", or even less. Anyknow know or know of someone who would know? Thanks a bunch.

 

[Owen]

It will depend on the gun. A .22 has a set length for optimum velocity, because the energy is relatively constant from gun to gun. A CCI Standard Velocity is a CCI Standard Velocity.

The optimum length in a Spring Piston gun is going to depend on the Spring Rate, weight of the Spring, the Volume of the Air Cylinder, the mass of the piston, the mass of the pellet. Secondary effects will come from how tight the pellet fits in the bore, and how much the air pressure causes the pellet to obturate, how well the piston is sealed, how good the seals are in the chamber of the gun, and the orientation of the gun. The path the air has to flow through will also have an effect. At lunch tommorrow, i will try to work up an equation.

owen