Over adjusting a Tau 7 = leaking?

[Daniel L]

Hi - I just bought a Tau 7 silhouette model in .22 and I wanted to know how far I should turn the screw.

I managed to turn it as far as it would go in before the screw diver hit the spring guide and it seemed to have a good level of power, but the cocking hammer is pushed all the way to the rear. i.e. its pushing the valve stem

I assume this means the valve is opened and therefore leaking unless cocked.

So should power be adjusted until the point where the valve stem returns to its full extended position, or can the hammer be pressing on the valve stem slightly?

Is the valve opened when the stem is pressed a little or is it opened only when the hammer is fully back?

Thanks,
Daniel in New Zealand

[Warren]

Haere mai, Daniel.

You probably should not wind up the hammer spring all the way, as you're probably not gaining a lot of velocity over wasting a lot of gas. If you can get a hold of a chronograph you'll see that velocity peaks out at a certain stage, after that you're just expelling way too much gas.

The hammer spring almost always opens the valve when there is no pressure in the gas chamber. But when the gas chamber has gas, the greater pressure seats the valve and stops leakage. But because of this you should always cock the gun before charging with gas, because sometimes the gas bypasses the valve and empties a bunch of gas out the barrel. Other times the gas pressure seats the valve, but it's a matter of luck.

HTH
Warren

[Daniel L]

Thanks Warren - that's very informative. I didn't think of gas pressure helping to seal the valve. Otherwise theres not much velocity adjustment before it hits the valve stem.

I will set up my chrono (have to get an indoor set up one day) and see how it peaks.