Now, it's New Years and I won't say I haven't imbibed a bit (a lot) here, but Glem to answer your question, probably with spelling errors, a spool valve works via a dynamic "toob" (speaking in inventor speak, you probably wouldn't understand since you've never invented anything..) that rides another "toob" which seals off a dump (volume) chamber. At a certain point in the "toob's" travel (in paintball this would be the bolt), "toob" driven by low pressure (60-120psi) air from a LPR (low pressure regulator,) it breaks that seal with the other "toob" which seals off the dump chamber. The dump or volume chamber can then be expended, pushing your projectile down the barrel while the tube is forward or open. It is an extremely efficient design, spare the waste air from the LPR. In paintball when spool guns first came on the scene at 150-200psi operating pressure, this was much lower than the standard poppet operating pressures of the day at around 300-1100 psi. I will say that some spools, worse if not tuned right, can be much bigger air pigs than a tuned poppet due to their ability to dump more air if you have a long dwell time, not enough lube, etc. Most spool paintball guns now operate at under 150psi, with under 100psi not unheard of.
Hopefully that kind of sort of answers your question about efficiency... and hopefully I've contributed something worthwhile here. The main tuning aspect on these guns is HPR/LPR pressure and dwell time (LPR air direction controlled electronically via solenoid)
Happy New Year again, folks!
this grammerman might be him lol, they sure do sound alike, maybe they are brothers 
