Are you just doing some research, or are you considering purchasing an FWB 124/ or you already have one?
You can make your FWB 124 a much nicer rifle with the addition of the ARH spring/seal kit, AND the right lubes. By installing the ARH spring and seal kit the velocity goes up, while the vibration upon firing noticeably decreases. That's a win-win. The cocking effort slightly increases compared to the factory set-up but barely enough to notice. After you've shot 100 rounds you won't even notice the difference anymore, unless the only springers you are willing to cock are an R7/HW30 or a CZ630.
(BTW, my memory says the OD of the piston seal once installed in the compression chamber of the FWB 124 is VERY close to 1.100" (plus or minus a few thou), but my memory may be playing tricks on me because it's been a while since I tuned one).
Here's the ARH spring and seal kit I mentioned:
For the best results you'll want to get some moly paste and spring tar if you don't have some already. Easily done! ARH also sells a lube package that includes both of those (and another useful lube ) for $24. It's here:
Like I said, if you're only doing research and don't need any parts or lubes for the rifle maybe the links will be useful to someone else.
Safe and Happy Shooting!
Ed Krzynowek, The Airgun Tune-Meister
"We can rebuild the squirrel. Make him stronger, faster...We have the technology"---Skyler M.