Tuning Anemic FWB124....

[218bee]

have a beautiful early FWB 124 thats shooting H&N FT specials (8.6 grs) at an anemic 600 fps. I recently put in a new full-power spring and hand fit a new piston cup, also did a very light black tar lube....but after a tin of pellets, it never "broke in" and got better. Heard these things will go into the 800 fps range when properly tuned. Seemed to be an easy disassembly, after I built a spring compressor...but maybe I missed something? Breech seal is perfect. Id like to get her into the 800 fps range. Any help here would be appreciated.

ds1911 (at) iCloud.com

218bee

 

[Odoyle]

https://www.gatewaytoairguns.org/GTA/index.php?topic=112217.0

 

[thumper]

I've had a couple early ones and they both sucked. Tubes were small, and both had tight spots at the end. Thats a good recipe for never making any power. 

The piston seal needs to be fit for light resistance, if it's too tight it will rob a lot of power. Check how it feels all the way down the tube. 

 

[KWK]

https://www.gatewaytoairguns.org/GTA/index.php?topic=112217.0

That's a pretty good post. anotherairgunblog has good instruction (you could skip taking the trigger apart). Only thing is the guy didn't follow Derrick's trigger adjustment procedure in part 2. He "finished" his gun without adjusting the trigger properly. FWB 124 has a fairly good 2 stage trigger IF it's adjusted correctly.

 

[GoldenStateAIRGUNer]

I have a early model and it's a 800 fps gun with JSB 8.4 gr. Make sure the breech seal is good. Try the tissue test.

 

[218bee]

Passed the tissue test. It's the internals. Tried to pre-load the spring more, but that didn't help. What's the preferred hi-power kit for these? Probably just need a spring at this point, since seal is new, correct?

 

[GoldenStateAIRGUNer]

Passed the tissue test. It's the internals. Tried to pre-load the spring more, but that didn't help. What's the preferred hi-power kit for these? Probably just need a spring at this point, since seal is new, correct?

Wonder how the piston seal fit is ? The piston shouldn't just drop into receiver tube nor should it require eating your Wheaties to push it in. How much force did you encounter? Did you debur all the receiver tube's potential sharp edges and polish them ? You may have knicked the seal. Another thing to try is a different pellet. My RWS 34 in .22cal only shoots the 14.35 gr JSB pellet @ 680-690 fps. But the RWS Superdomes at 14.5 gr and Sig Venom (also at 14.5 gr) shoot 750 fps ! I'm shooting the JSB 8.44 gr (4.53mm head) in my 124D. Try those ! The rating for the 124's back in 1977-78 was 800+ fps. That was with light (7 to 7.5 gr) pellets. Later models had the velocity at 820 fps. 

 

[PumaCarl]

I have heard of aftermarket piston seals being off sized. Your seal is most likely nicked or just not correct. FWB124 were the model for setting the 12fpe rule and they pretty much hover right around it. I have replaced internals before and there isn't that much of a difference in velocity between being broken in and new, it just gets a little smoother and it doesn't take long. Your gun definitely has problems, don't settle for 600fps. The only springer that I have personally seen with that off of a velocity had a broken mainspring. Unlikely, for yours being new, but it's possible.

 

[Motorhead]

Seal fit is crucial on these rifles. Too snug and power drops like a rock !!!

 

[218bee]

Thanks guys. The green seal came from a reputable place, like Pyramyd Air, etc, the spring was a brand new 18-Joule model from Nikko's in Canada, and looked almost identical to the original spring. The seal was tight at first and I carefully reduced the diameter on my lathe to where I felt it was a perfect fit. Then a light lube only on new spring and rearward of seal face. I confess it was my first tune, and maybe I didnt take enough off the seal? The rifle is smooth as hell, just can't get her past 630 fps with an 8 gr pellet.



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[AirShot]

Once the seal is fitted, check the new spring for wire diameter and number of coils. Some replacement springs have a smaller dia wire which means a little less power. Same with number of coils, just because a spring looks the same doesnt mean it performs the same. 

 

[Motorhead]

As too speed .... in there day Robert Beeman had the FWB 124 specs at @ 810 fps using the 6.9 grain laser pellet.

So if shooting with 8'ish grain pellets ... do keep that in mind and adjust expectations based upon @ power less so than speed.

 

[Odoyle]

MARFLOW-? PM ME SINCE I'M UNABLE TO CLICK YOUR PROFILE TO SEND A PM.

 

[Odoyle]

Passed the tissue test. It's the internals. Tried to pre-load the spring more, but that didn't help. What's the preferred hi-power kit for these? Probably just need a spring at this point, since seal is new, correct?

Likely needs honing.

 

[GoldenStateAIRGUNer]

That seal m is the same as mine. When I had my barrel off to replace the pivot bolt I could shine a light down the transfer port and see my seal is green. It's true most 124's hover in the 12 ft lbs range. Light pellets tend to produce the higher energy figure. With the JSB's mine is in the 11.8-11.9 range. Will easily do 12 with light pellets. Some special tuned 124's can hit 13 ft lbs. I'm thinking your spring and/or the breech seal is the problem.

 

[rob_g]

I put a Maccari kit in my 124D last year. I'm getting 763 fps with JSB 8.4 pellets over a couple different chronographs 

 

[GoldenStateAIRGUNer]

I put a Maccari kit in my 124D last year. I'm getting 763 fps with JSB 8.4 pellets over a couple different chronographs

What elevation are you at ?

 

[rob_g]

I put a Maccari kit in my 124D last year. I'm getting 763 fps with JSB 8.4 pellets over a couple different chronographs

What elevation are you at ?

I'm at approx 1100 feet here

 

[GoldenStateAIRGUNer]

I put a Maccari kit in my 124D last year. I'm getting 763 fps with JSB 8.4 pellets over a couple different chronographs

What elevation are you at ?

I'm at approx 1100 feet here

Not much velocity loss at that altitude. Probably 10-15 fps. I'd say your 763 fps is about what mine would do at your altitude. Mine does 800 fps at 85 ft elevation.