FWB Piston rings and piston buffers?

[specie]

On spring piston airguns like FWB150-300S that has both a metal piston ring AND a piston seal, does the metal ring act as automotive compression piston rings, and the piston seal just provide "buffering" to prevent the piston from slamming into the compression chamber face?
Also, on airguns without the metal ring like Weihrauch R7, HW55, R9, etc, the piston seal must do both the compression and the buffering?
It seems that with a metal compression ring the gun will still work even without a good condition piston seal "buffer"?
Or maybe the piston ring is just acting as a "button" to keep the piston properly centered in the receiver bore???

 

[Chuck-in-Ohio]

My vote goes to the ring sealing the compression cylinder.

I will have to search it out, but FWB calls out the piston ring dimension, and mandate replacement at a point.
I will pop back with info bits when I can track them down.

 

[Ievgen721]

Yes, that's right, my FWB-65 works without changes, without a seal and a buffer, they just fell apart. But shooting without a buffer can lead to breakdowns.

 

[marflow 777]

the story i have read is the piston ring is good for 100,000 shots and for my money i would not change it because the piston and ring have live with the cylinder and are mated very well together
i guest if you had club gun and it was shot by everyone since new it could be time
the buffer is just that a buffer
story
i have a FWB 90 and you can see the buffer from the outside and it was the factory original white cream colored one and i decided it needed changing just because and if you have been in one of these before they can be more than nerve racking, pricy pistol first time inside and lots of small parts at the sledge
but the buffer was in great shape but was changed anyway because i was not going to be inside the pistol again

 

[Chuck-in-Ohio]

The info I spoke of earlier has apparently vanished along with the forum where it was posted......

An new OEM FWB piston ring measures .036 in thickness. FWB recommends they be changed out at a certain wear point as it wil allow the rings end gap to increase, allowing more blow by and lower pellet velocity as a result.

 

[marflow 777]

change the subject for a second
at some point last year someone was looking for a trigger carrier for a FWB 300 and they were no long available which was bad news but
i was just over on Waffencenter Gotha and they are making them and offering them for sale for 25 euros bring one to the states would be stupid but bring a dozen could be a way to go for someone

 

[MDriskill]

On spring piston airguns like FWB150-300S that has both a metal piston ring AND a piston seal, does the metal ring act as automotive compression piston rings, and the piston seal just provide "buffering" to prevent the piston from slamming into the compression chamber face?
Also, on airguns without the metal ring like Weihrauch R7, HW55, R9, etc, the piston seal must do both the compression and the buffering?
It seems that with a metal compression ring the gun will still work even without a good condition piston seal "buffer"?
Or maybe the piston ring is just acting as a "button" to keep the piston properly centered in the receiver bore???

On the FWB's, the metal piston ring fits the cylinder wall very snugly and is the air seal, not just a centering device. The piston bumper does not help compress air. (The ring is sized so that it springs out to tightly fit the chamber walls. So it's basically impossible to wear it out, but as C-i-O noted, over time wear increases the tiny gap where its ends meet, thus reducing velocity due to air leakage.)

Although the resilient plastic (or leather) seal in a typical springer does provide a degree of cushioning at the very end of the piston's travel, most of the piston-braking effect comes from the highly compressed air trapped between the piston and pellet (this is why it's so important NOT to "dry-fire" an un-loaded action). Much of this air is trapped in the transfer port - which brings us back to the FWB's.

An overlooked but ingenious feature of these guns is the tapered breech end of the barrel, which reduces the transfer port to near zero length. Removing the "lost volume" of a TP port helps get maximum power from minimum-strength mainsprings; and keeps the recoil-control "sledge" system as light and simple as possible. But the TP's piston-braking effect is mostly lost, and thus the bumper on the front of the piston is very important.