I was not looking for another project but when I filled my Grand Prix with my Xisico compressor I was surprised at how long it took to reach 200 bars.
After unhooking it I could feel some air coming from around the quick connector filling nozzle.
Information for both the Grand Prix and the Atomic is very scarce but I was able to find a few posts and one of them was specific to the filling nozzle.
It seems that it is a three parts business with the barrel band sandwiched in between. The only part easy to remove is the quick connector nozzle which only requires a little wrench. The other two are completely round and I have no clue how tight they might be. Since the problem doesn’t seem to be there, I will leave them alone.
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There is no degassing option for the Grand prix so I dry fired it until empty. After removing the nozzle, I inspected the o-rings which seemed OK and pliable. It was not leaking from the check valve so the guilty one was probably the one enclosed by the steel washer. Some airguns have a bounded steel washer and rubber seal (see picture below) but this one just looked like it was a regular o-ring sitting inside the washer. I could notice that there was a black residue like a thin coat of rubber inside the washer but there was an area where it was missing. I scraped all that and sanded the inside surface smooth.
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Measuring the neck of the nozzle and the inside of the washer told me that I needed a 5/16” x 7/16” o-ring. When the original o-ring was placed inside the washer it fitted perfectly so I decided to just lubricate everything, reassemble the parts and try to fill it. The leak was still there.
I checked the cross section of the original o-ring and I got .065” and from one of my boxes I got a larger reading at .068” and smaller at .060” from the other. I know that there are some tolerance variations but the thickness of the washer being .076” there is no way that the 5/16” x 7/16” imperial o-rings can seal.
Looking in my metric box, I found a 2mm x 6mm which has a .077” cross section. It was a bit bigger than the 7/16” OD but could be massaged inside the ID of the washer. This was probably the best candidate.
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I lubricated it, inserted it on the neck of the nozzle then tried to add the washer. I couldn’t get the o-ring to slip inside the washer. The washer has a side that is flatter than the other so I thought that if I placed the rounded edges face towards the o-ring there might be a chance that it will compress into the space once tightened. I slowly screwed back the nozzle and it went in, so I filled the pistol with the compressor and there was no leak.
Another problem solved.
R-Gun Pete