New to PCP & having a pump problem.

[Timberwerks]

Hi Guys

It's been awhile. I just got back into pistol shooting with a new Hammerli AP20 Pro & a Hill MK 4 pump. Previous pistol was a IZH 46M. The problem I have is when I fill the cylinder and unscrew the pressure release of the Hill pump all the cylinder pressure releases as well. What am I doing wrong? If I unscrew the cylinder from adapter there is just the quick burst of air but the cylinder is still charged.

Should I not be using the supplied MK 4 hose and quick connect and screw the adapter directly into pump? Or, is there a pump problem?

Thanks

[TenMetrePeter]

"If I unscrew the cylinder from adapter there is just the quick burst of air but the cylinder is still charged."

I would think that is what you should continue doing then.

All depends if the cylinder has a push-in valve pin which the adapter holds in. Sounds like it does so do the above.

[Timberwerks]

Thanks

The Youtube videos I watched all mentioned that the relief valve should be opened. They all showed the filling of rifles and didn't mention what to do when filling a pistol cylinder. I didn't know about different valving etc.

[ML1944]

I had almost the same problem. I fill from a scuba tank, not a pump, but the principle is the same. My previous experience with PCP involved cylinder valves that worked off of pressure differentials. You attach the empty cylinder to the fill adapter, open the main valve on the SCUBA tank, the pressure differential opens the valve on the cylinder and when the desired pressure is reached close the main valve and vent the fill line. The drop in pressure in the fill line closes the valve in the cylinder and your good to go. I purchased a Walther LP400 and found out their cylinder valves open mechanically by direct contact from the fill probe. When you attach the fill probe the tip of the probe depresses a stem on the cylinder valve and opens it. If you try to vent the fill line before you release the valve the whole cylinder will vent. After talking to the Walther service center I worked out a system where after filling the cylinder and closing the valve on the SCUBA tank, I partially unscrew the cylinder from the adapter ONLY enough to release the valve but not so much that the seal between the cylinder and the adapter is broken. I then vent the fill line and all is good. I find that the sweet spot is between 8 and 10 half twists. Not enough and the air goes out the vent valve. Too much and the air leaks past the adapter seal. I seem to get it right most of the time now. Since Walther owns Hammerli, I would guess that the fill process might be the same. Drove me nuts until I spoke with Walther. I thought I had two bad cylinders with a brand new gun.

Experiment, you will find that spot where it works without spilling any air,
Mike

[ChipEck]

With the Hill pump, after you get the desired pressure you have to slowly unscrew the air cylinder about 1 1/4 revolutions. Next open the bleed value on the Hill pump. Unscrew the cylinder the rest of the way. Do not forget to tighten the bleeder value on the Hill pump. Just light finger tight is all you need.

Chip

[TenMetrePeter]

The advantage of the adapter pressing in the valve is the pump doesnt have to open both valves every stroke, and with scuba tanks you dont get that sudden break followed by the whine of the valve vibrating.
Disadvantage is you need to screw cylinder in and out for a couple of turns against the pressure.

[Timberwerks]

Thanks for the replies!