I picked up a 124 deluxe JNC from ChuckHunter and would like some tuning info. Any input would be appreciated.
Tuning FWB 124
- Thread starter GoldenStateAIRGUNer
- Start date
I was shooting it. It has a soft tune and was shooting JSB doomed weighed at 8.3 gr 640 fps. Yesterday morning I pulled the stock and used Vibra-Tite VC-3 on the stock screws. Then shoot a few more 8.3 gr JSB's over the chrony for 670 fps. Then all of a sudden I started getting shots in in the 590-605 fps range with same pellet. I'm thinking the piston seal has issues or the mainspring broke. ??
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Breech seal o-ring is what I would replace first and if you are lucky you may be able to flip it around for a temporary fix till you get another matching size from ACE Hardware or Lowe's or Home Depot or local hydraulic hose shop. Bring it with you to size match.
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Scott told me a trick to check the breech seal. Place a kleenex over the breech area and fire the rifle. If it leaks you'll get a puff of air under the kleenex. In my mind if it was a breech seal I would have had low velocities on every shot. The high, and then low, variations are what makes me think piston seal. I'll check it in a little while. Still in coffee in bed mode.
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You may have had a little oil which migrated into the compression chamber too to diesel it to spike high velocities that goes away by itself after many many shots. That's why I suggested just shooting it for a while first.
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Just did the kleenex test and it probably shot about six inches up. Breech seal. Should I go OEM feinwerkbau or are there better aftermarket seals ? Wonder if the barrel pivot bolt is worn ?
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They are built very well and I highly doubt you have a worn barrel pivot bolt.
ACE Hardware match an o-ring from their drawer. You can try and flip that squashed o-ring around as a temporary fix.
I crack the barrel open a little (not cocked) to not squash the o-ring on my break barrels and SSPs and side and under levers wedged a little open by using a golf tee or popsicle stick when stored. Run a light film of silicone oil or divers grease to avoid drying out and cracking.
Others might say it's useless to do so but it's just me and have lots of guns that aren't used for long periods of time and expect no surprises when I decide to shoot any one of them...
ACE Hardware match an o-ring from their drawer. You can try and flip that squashed o-ring around as a temporary fix.
I crack the barrel open a little (not cocked) to not squash the o-ring on my break barrels and SSPs and side and under levers wedged a little open by using a golf tee or popsicle stick when stored. Run a light film of silicone oil or divers grease to avoid drying out and cracking.
Others might say it's useless to do so but it's just me and have lots of guns that aren't used for long periods of time and expect no surprises when I decide to shoot any one of them...
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O-ring is METRIC and should be of 90 duro hardness to survive service as a breech seal. 70 will work in a pinch.
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Even a couple thousands of an inch wear on a pivot bolt could effect the seal quality. I just ordered a new pivot bolt assembly. Only $40 so worth the potential help with this breech/receiver seal issue. Next a breech seal.
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I've always wondered what the tissue test looks like when a breach seal is leaking.
That is quite obvious. Thanks for sharing.
That is quite obvious. Thanks for sharing.
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and the other from 
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