Rifle sat too long

May be the regulator is sticking?

I always try to start with the cheapest and easiest thing - How is the breech seal o-ring? Did you perform the 'tissue test' where you dry fire the gun with a tissue laying over the magazine slot, and see if it blows off?

Could be as simple as lubing the breech seal o-ring (I use O-Ring Super Lube applied on a bent q-tip swab). And if that doesn't do the trick you might have to replace the dried out o-ring, if that is indeed the issue (tissue test will say whether it is).

Most likely have o-ring issues and possibly some metal sliding parts that no longer move as smooth or consistent as they did when new and properly lubed. You will probably need to take things apart and fix those problems. A friend of mine that wanted to get into pcp bought one of my old first pcp rifles that I sold to a friend years ago. The rifle has sat for years cause that friend stopped using it. We went and picked it up knowing it may need some work like o-rings needing replaced even tho the airtube had the same amount of air he put it away withyears before. It shot good for about 2 days then fell apart. Everyo-ring ended up needing replaced from drying out and rotting. Once everything started moving and getting used again the o-rings started to come apart.

TMH has a good suggestion for the first steps I would add that I wouldnt dry fire it I would shoot a pellet. Dry firing may not create enough resistance to cause the air to push against the oring enough to bypass the dry or faulty oring.

So where exactly does the velocity start at from a fill and with what weight pellet? It ramps up 100 fps per shot? If so to what point and does it ever stabilize ?

sounds like a fried oring to me .. just get a full set together and rering it .. debur any sharp adges around them as you go ..

I have seven FX guns, a RAW HM100X ,HW100 and a few others. Started buying these beginning 2018 and put all in storage except for one Impact MK1 which I've been using at a low rate since March 2018 and no leaks yet. However the RAW and HW100 new in box in storage are leaking. All were stored with about 3000 psi nitrogen. My question is as follows....would it not be better to store long term at zero pressure? That way the orings are not deformed under pressure. If stored pressurized long term the orings compress into different shape and over time they will then take a permanent set. Now when varying the pressure the set, deformed orings can no longer seal the surfaces they were selected for?

sltech said:

I have seven FX guns, a RAW HM100X ,HW100 and a few others. Started buying these beginning 2018 and put all in storage except for one Impact MK1 which I've been using at a low rate since March 2018 and no leaks yet. However the RAW and HW100 new in box in storage are leaking. All were stored with about 3000 psi nitrogen. My question is as follows....would it not be better to store long term at zero pressure? That way the orings are not deformed under pressure. If stored pressurized long term the orings compress into different shape and over time they will then take a permanent set. Now when varying the pressure the set, deformed orings can no longer seal the surfaces they were selected for?

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This is a good question, and myself would like to know the answer. I am quite sure that zero pressure is not good for the inner parts because allows moisture in. So I would think that the answer is somewhere around 1500-2000 psi which is below the operating pressure. I think that keeping the orings from drying out is the bigger concern vs storing them pressurized at their high operating-limits of 250-300bar.

Hence the reason im a firm believer to add a couple of drops of silicone oil into your fill whip that’s connected to your fill tank, every third or fourth top off, and for sure if your topping off the gun and planning on putting the gun away for a spell.

When you open up the scba’s valve the oil will inject into your guns presdure tube/tank and as you shoot and top off, the oil will disperse throughout the guns o rings, regulator, and valve system. Last place out is the oil gets shot out the barrel.

What made me start down this path as part of pcp maintenance was on a used impact I acquired, the fill gage says 250, reg gage said 125(after a top off), and next morning reg gage shows 210. I had just acquired this gun, so I knew nothing of its quirks.

I take the regulator out and all four o rings on the reg were bone dry, and the worst one was the 10 x 1.5 inside the regulator tunnel. Hard and brittle, and was a pain to get out as it seemed cemented against the groove it set in.
New o rings with fresh lube and no more air creeping by the reg. That’s been around 8 months ago, and with the regimen of injecting silicone oil every fourth top off on the gun, my guns are leak free. I have a Hatsan bully, a PRod, and a marauder that I haven’t shot in over a year and they still are at their fully pressurized levels when I last topped them off. The plus with this is my regulator responds well, and stays exactly where it’s set at.

Too much can be a bad thing, so make sure to not overdo it with the oil. Like I said, about two drops every fourth top off. The o rings in your fill whips QD or fill probe will thank you also.

Our PCP guns are no different in lube requirements like a pneumatic air tool. My Senco finish nailer, it comes with a small container of oil. It says in the instructions to add two drops into the male QD before attaching the air hose, at each use. Same concept