FWB 65 repair

[Ranb]

I bought a FWB M65 a while back. It appeared to be in very good condition with a slightly worn seal up front. $680 from an auction site. Last week it suddenly started shooting 196 fps instead of the usual 500 or so.

I bought a new seal kit and ring. Below is the condition of the old seals. It should shoot much better now.

[thirdwheel]

Well done!
looks about the same crumbly mess I had some years ago when I decided to get into 10m and bought a 65, being an engineer I set my bench out to change the parts but it took three times as long as it should as I spent so much time marvelling at the engineering, it was a complete joy to look at and analyse. I service my own pcp pistols and they are very simple compared to the 65. Goodness that was expensive, but it is pleasing the service parts are still readily available, I changed my piston ring and spring but on reflection mine only really needed the rubbery bits.

[spektr]

If you have a pistol you love, like this. You need to ask the question, "do I salt away 1 more rebuild worth of seals or not". I just started to buy seals for my CPM1 since it leaked, I bought 2 sets. I think the gun will outlive me now, but i can reseal it again if it doesnt......

[Ranb]

When I bought the pistol months ago I noticed that the little white buffer under the seal was brittle and flush with the cylinder, but I didn't know this indicated it was in poor condition. The seal in front looked good enough and I got 474 fps with a 3 fps stdev over the chronograph. I guess the buffer on the piston just crumbled all at once.

I'll be on the lookout for cheaper replacement parts in the future.

[kevinweiho]

When I bought the pistol months ago I noticed that the little white buffer under the seal was brittle and flush with the cylinder, but I didn't know this indicated it was in poor condition. The seal in front looked good enough and I got 474 fps with a 3 fps stdev over the chronograph. I guess the buffer on the piston just crumbled all at once.

I'll be on the lookout for cheaper replacement parts in the future.

When you see a flush white buffer on an old FWB 65/80/90, it's an indication of a rubber compound, which is also used in the piston seal as well.

They will disintegrate and crumble overtime even with no use. The newer seals are made of a synthetic material, will last a very long time.

If you have a lathe, you can churn out your own custom seals with polyurethane rods...

[Ranb]

I have a lathe that I make silencer parts on. I'll have to give the seal a try. Can you tell me exactly what kind of polyurethane is used? It seemed to be a hard rubber material.

I tested the pistol with a chronograph today. 497 fps with a stdev of 3 fps. Accuracy is back to what it was. My pistol was made in the 1980's and has two main springs.

[kevinweiho]

Can you tell me exactly what kind of polyurethane is used?

I don't know the exact polyurethane used, various forums mentioned using rods of 95 A Durometer urethane to make their seals.

[Gwhite]

Machining polyurethane is tricky. It's used for seals because it is tough & abrasion resistant. You'll need super sharp tools. For working with rubbering things, freezing it may help.

[Ranb]

One of my friends has a FWB65 that is missing he rear sight leaf spring. While I had mine apart for replacing seals, I measured my spring and made a replacement from some steel. But I forgot to measure the size of the cylinder head screw that holds it in place. I don't have ready access to my pistol at this time.

Anyone have the length and thread pitch? Thanks.