Help Erratic Velocity!

[Se7en]

I have a level 7 68 automag that i run off compressed air. For some reason it has very erratic velocity. Ill be at a chrono station and shoot 280 one shot and then the next will be 195, then 250, then 225, then sometimes as low as 88fps. I have all stock internals and a crossfire 68ci 3000 psi tank. what do you think that is causing this erractic velocity? ANY help would be greatly appreciated.

[Xen]

feal the tank, if its hot or you just filled it, that may be the problem. But I haven't seen it spike that much due to a freshly filled tank

[FrAuStY]

Take the internals off the gun. Unscrew the Reg (back half) from the Valve. Be careful not to lose the valve pin. There will be a yellowish clear reg seat should be stuck in the back half. Take this out and clean it as well as the two mating parts (Reg and valve where it would touch. Dab some oil on your fingers and lube up the seat. It should go on the same way it came off.Put it all back together and see if that helps. If not.. get a new reg seat. Almost anytime you have velocity problems with a Mag.. its due to a leaking or bad reg seat.

[Xen]

a just filled N2 tank (Atleast steel ones) become hot from the presure inside the tank. Take off your tank cover and let it cool.

[PyRo]

Replace the reg seat.
If that doesn't do it, you probably have a bad spring pack.

[FrAuStY]

Are you chronoing the gun as you should? Holding down the trigger between shots? This keeps the dump chamber from heating up due the quick recharge rate. When you're on the field shooting quick bursts and ripping on the trigger the spikes tend to level off due to constant air flow through the valve. Its only when you shoot one shot.. then wait a while..then another shot that the spikes come in. Go to www.airgun.com click tech support and then click the link for chronoing the R/T it explains all of this and more in there. :)