FWB P40 absorber and its adjustment

[CROB]

My FWB P40 absorber behaves a little odd. I've spoken to a gunsmith but didn't get much help. Gun is 4 months (and about 5-6000 shots) old.

The manual says that you adjust it by firing a shot (must have a pellet) keep the gun horizontal, then slowly open the breach until resistance is felt. This is where the absorber has come to rest. It should be 3mm from the reference line.

My problem is that it varies from 0mm to 8mm randomly. Although it is subtle, I think it is giving an inconsistent feel to the shot, occasionally causing more muzzle flip. I think the absorber is some type of dash-pot, but without disassembling it (ok i'm not that brave) I'm guessing. Even trying to do the adjustment, sometimes it is harder to move than others.

Anyone else with a P40 gor any insights?

[Nano]

Crob:

I have a FWB P40 too.
I shot about 1000 pellets a week, for the last year I use the P40 without problems with the absorver, the absorver works easily 3 or 4 years without maintenance.
the pistols FWB p34 were already including the absorver. There are ancient guns P34 that have never done maintenance and work perfectly.

Enjoy your pistol, shot 10, and dont think in the absorver for the next 4 years.

Nano

[Guest]

Hi CROB, shame no owners have been able to help you.
Looking at the 10P files, its a bit hard to see how it all functions.
If what you describe is correct, there is definitely a problem somewhere.
Could be anything from a loose screw, broken spring, machining burr, oil/grease where it shouldnt be, etc.
Before stripping it, I would maybe try adjusting it from one extreme to the other with the hope of freeing /settling something.
If after returning to the desired position it still gives erratic results, it will need taking apart in the absorber area to find the problem.

[CROB]

Guest said:

Before stripping it, I would maybe try adjusting it from one extreme to the other with the hope of freeing /settling something.
If after returning to the desired position it still gives erratic results, it will need taking apart in the absorber area to find the problem.

Thanks for your feedback. This is what I thought I would have to do, I just hoped there might be a known answer. There is a screw that adjusts the absorber, and I've turned it a few turns each direction without any improvement.

I think the problem is lack of lubrication. The manual says don't lube anything. But as an old FWB user told me, they always say that but eventually some silicon grease is needed in a few areas.

Thanks again Guest.

[Guest]

Hi again CROB,
When you have it apart, just check for the other things I mentioned.
Also, make sure the lubricant you try isn't one that drys to leave a sticky or hard residue. Quite a few of them do as a preservative against corrosion.
Good luck and let us know how it turns out.

[CROB]

Good luck and let us know how it turns out.

Well I took the recoil absorber apart. Relatively straight forward, you just need to remove the obvious parts and drift out the pin that holds the breach cover. Be careful of the spring loaded button on the damper mass, and the pin that seals the bolt (see below).

There is a small tapered pin (or piston) that seals the end of the "bolt". This is driven backward by air pressure and pushes against a heavy mass. The mass is a close tolerance fit inside a 12mm (guess) cylinder in the rear of the bolt. The mass has a spring loaded teflon "button" that rubs hard against the inside of the cylinder it sits in. The adjustment screw for the absorber alters the pressure of the button. Effectively, it increases the drag required to push the mass backward.
(I should have taken some photo's with it apart).

The only thing I could find was rather sticky lubricant. The mass needed some lube, and the piston was sticking in the bolt. I gave the parts a good degrease, wiped everything clean and dry and applied some Rem Oil (only because it is less sticky than Gun Moly). There are no seals in this area - it is just metal to metal.

I'm off the range tonight to test fire and adjust it.

[Guest]

Sounds like the sticky lube will be the problem.
A lot of them start out nice and liquid, but over time they dry out and leave that sticky or hard residue.
Hope all is good now.

[Nano]

Crob:

supposing that I want to regulate the absorver to have a little of recoil, ¿ can I slacken the screw of regulation?

I say this, for which I have read in the interview Mihail Nestruev where he say that he regulated his Steyr air pistol to have a little of recoil.

Thank you for your post,

Nano

[CROB]

supposing that I want to regulate the absorver to have a little of recoil, can I slacken the screw of regulation?

Yes, if you make the screw tighter you feel more recoil. If you make it too loose you get a delayed pulse, a bit like the recoil from the slide on a semi-auto.
With it set per the adjustment in the manual it cancels out the recoil pulse quite well.

If you tighten the screw fairly tight (a few turns), you can effectively disable the recoil absorber altogether.... But I definitely prefer it working per the factory settings!