Spotting Failing FWB 65/80/90 Seals and Damper

[Bad News Beeman]

Hi guys, I've been lucky enough to pick up a couple FWB pistols including the Model 65 and 80. I'm scared to death of shooting them though knowing what I do about the risk of destroying the detent lever if the seals and damper have deteriorated. Ever since learning from David Slade that it can take as few as just a couple shots with bad components to break off the tab of the lever, I've been leery to do anything more than a single shot to test function. Last thing I want to do is snap a part that has been discontinued and is now virtually unobtainable.

My question for those more experienced, how can I identify if my pistols are okay to shoot vs need to be immediately resealed? Obviously a crumbled piston seal is a dead give away, but take my Model 80 for instance which appears to have a decent seal, but the damper looks a little worse for the wear:





What's the verdict on something like this? And what's generally the rule of thumb when inspecting these pistols and determining if they're safe to shoot?

[Yogi]

If they have been resealed in the last 10-15 years you should be fine.  They have made Huge strides in piston seal materilar technology.  Thanks partly due to skate boarders.

Run them across a crony one time and see if they are near spec.  Know what spec is!

-Yogi

[Bad News Beeman]

If they have been resealed in the last 10-15 years you should be fine.  They have made Huge strides in piston seal materilar technology.  Thanks partly due to skate boarders.

Run them across a crony one time and see if they are near spec.  Know what spec is!

-Yogi

What if I don't know when/if a reseal has even been done? These in particular came to me from an estate flipper that didn't know their history.

[Yogi]

When totally in doubt, change them, relube and be good for the next 30 years...

-Y

[MDriskill]

The little snubber (white thing under the breech seal) is about due for replacement. Its job is to push off the auto trigger-blocking safety (the tab sticking up under the breech end of the barrel) when you close the action; when it fails the trigger won't release. In your last pic, it looks like a bit of the snubber has flaked off and is stuck on the tab.

The other vulnerable piece is the bumper pad on the front of the piston. The red flag there is seeing chunks in the barrel, then it's time to stop shooting and get an internal rebuild. 

The actual piston seal is a steel ring similar to an automotive piston. It and the blue breech seal may outlive us all!

[Bad News Beeman]

The little snubber (white thing under the breech seal) is about due for replacement. Its job is to push off the auto trigger-blocking safety (the tab sticking up under the breech end of the barrel) when you close the action; when it fails the trigger won't release. In your last pic, it looks like a bit of the snubber has flaked off and is stuck on the tab.

The other vulnerable piece is the bumper pad on the front of the piston. The red flag there is seeing chunks in the barrel, then it's time to stop shooting and get an internal rebuild. 

The actual piston seal is a steel ring similar to an automotive piston. It and the blue breech seal may outlive us all!

Thanks for this explanation! I didn't realize this is how that bumper worked.

[MDriskill]

This is going off on a tangent, but IMHO the conical tapered breech, and its seal, is one of the more ingenious details of the FWB design. This reduces the transfer port to basically zero length, thus eliminating the velocity-robbing "lost volume" of the longer channel in most springers. This in turn makes it easier to control recoil by minimizing the spring strength needed for the desired velocity.

But the trade-off is also losing the cushioning effect of that typical long transfer port, requiring the resilient bumper on the front of the piston.

Here's a link to the factory parts diagram and list. Again, the three perishable bits are the safety snubber (part no. 1600.125.3), breech seal (1600.122.3), and piston bumper (1600.124.3).

https://www.feinwerkbau.de/ceasy/resource/?id=569-0