Classic slow velocity decrease problem

[nulam]

Hello all,
My classic valve valve will slowly, over the course of a couple hundred shots, lose velocity to the point that there is not enough pressure to activate the level x. I can fix it by turning up the velocity but that is not always possible in the middle of a game (I don't make it a habit to carry velocity adjusting tools onto the field). This is also forcing me to chrono (excessively) before every game.

Any ideas?

[Maggot6]

What kind of tank are you using, and what pressure?

[nulam]

I'm running it on a Nitroduck 68/3000 adjustable HPA at just over 800 p.s.i. According to the gauge, the pressure output remains constant. Also, this does not seem to be shootdown due to air starvation. My guess is that the problem lies somewhere in the reg. piston, spring pack, or reg. valve pin and spring (german handgrenade).