Thought I'd share this, as I couldn't find what the problem was on here. Having installed my new Huma Air 2nd Reg and reassembled the rifle, as soon as I connected the air bottle, air started flowing out of the barrel and there was no air pressure build up in either reg. It turns out this is a FX/PCP newbie error, because I didn't properly understand how the FX guns work. It's the high air pressure inside the gun that holds the valve closed, but I had installed the Huma Air reg with the screw turned almost all the way in, as per instructions. This meant no significant air pressure in the rifle, not enough pressure to close the valve, so a trickle of air was instead just running through the valve and out of the barrel. Conclusion, (in my case after buying a whole new o-ring kit, new power block and valve kit) just crank up the pressure on the newly install reg! I guess I have learned something new and have lots of spares for the future, so not all lost.
