I pulled two Biller guns off the rack. One gun has a pull of 43 inches (rear of muzzle to sear box) and the other 26 inches. Measuring the distance from slack rubber (wishbone) to sear box, both of these guns have a tension span of 73% of total pull. Looked at another way, a full stretch is 1.37 X the actual stretch. Therefore, a roller gun should have 37% more stroke with the advantage occurring in the final stretch so to speak. I'm guessing that the average force applied during the final stroke is about 18% of the force at full tension or about 37% of the average force applied when discharged. This should result in an approximately 37% velocity beyond what a conventional gun would induce. However, since kinetic energy is related to the square of velocity it seems to me that the extra energy imparted to the shaft should be 1.37^2 or about 90%. Adding a second rubber to a conventional gun should give it 46% more velocity than a single rubber roller gun.I'm probably missing something here but.......One thing may have to do with time and acceleration force. Since the shaft is traveling faster as it goes down the track the increment of time that the accelerative force is applied is smaller during the final inches of travel than at the beginning. Since velocity = Acceleration X time the actual velocity imparted to the shaft may be less than expected. However, this same idea, if correct, would apply to conventional, multi-rubber guns as well. Thus, the guesstimate number may hold water a bit longer, at least until some objections are raised.
I'm editing as I go along, eg when more issues arise. Typically, when I sleep on it I change the whole thing (G). Anyhoo, how come that one expert, Monte, says that roller guns have minimal felt recoil (barrel lift) when Memo (the guy from Colombia) has added wings to suppress recoil? Something doesn't add up. Admittedly, adding wings (mass) is more convenient with a wood gun than a tube type. At least, the flotation isn't impaired. This may be a gray area of contention.
Pesky