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.
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.
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......
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.
Ranb wrote: ↑Tue Mar 16, 2021 5:02 pm
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...
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.
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.
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.