I'd say put an H&N 19.91 .25 over a chrony and see what the 135 does.I know I got near 750 FPS in the 125 Sniper.Will Chrony the 135 with that same pellet in a few days when I get home.
My 135 springer shoots H&N FTT 19.91g @ 827 fps for 30.1 fpe.
To change a barrel and increase speed you'd be changing the caliber. 1000 fps barrel is .22 cal shooting 14 grain from a 125, 135 power plant. You can't change the energy of a gun by changing out the barrel unless the barrel is shorter than potential energy to develop shot by time it exits barrel. The power these break barrels put out only need a 10 inch barrel or less. They are longer simply to act as a lever to cock the gun.
My non-QE 135 springer has the 17.7" barrel already. The QE version 135 has the 10.6" barrel. I have a 125 sniper springer with the same length barrel as well.
I understand what you saying. Greater swept powerplant volume should have greater barrel volume to take advantage of what is available. So if you go down in diameter, you go out in length, provided everything maintains enough of a seal to make it work.Could they also have reduced barrel length to alleviate some need for follow through?
You'd have to see what the crony #'s people with QE versions are getting compared to non QE versions. That's a 7 inch difference of barrel. Surely if it was significant there'd be a lot of talk and complaining on these threads about loss in 135 power since the QE change over. I agree there must be left over potential energy but believe it's insignificant amount. The power curve is a parabola, not linear expression, and the top of that curve is nearly flat for a wide range of barrel length. Think about it, .177 in 125 or 135 is proven to be less energy. From the learned guesstamate above the length of barrel would need to be 30" to tap out all the potential. Yet the energy drop of .177 from .22 or .25 cal is only a few foot-pounds in the 17" barrels, literally about 2 FPE. If we express volumes of barrels then a a 30" .177, 20" .22, 15" .25 and 10 inch .30 are the same. If there is significant loss of energy with the QE's then it would be most seen in .177 and .22 calibers. Are people reporting 25 FPE in those calibers? That would be 3 FPE loss with 7" less barrel in .177.