Power output of FWB 127 too low?

[NTSOG]

Hi folks,

I recently installed a US spring in my FWB 127. It came from Air Rifle HQ and is described as a "new super grade spring". The old [probably original] spring broke. The rifle is averaging 602 fps with a spread of 9 and a standard deviation of 2, giving 11.8 foot pounds with H & N FTT [14.66 gr.] It is very smooth, but I am wondering if the low power [by Australian standards] is indicative of a leaking or tired piston seal?? Unfortunately I did not test it with the original spring. What should I expect from the rifle, given some of the figures I have read in US articles?

Jim

Garibaldi, Victoria, Australia

[CapitalBee]

I'm not sure what the Maccari spring can achieve with the 127. However, for mine, which is running on an Ox (suitably trimmed down) I'm getting 11.8fpe. I'm not sure the internal swept volume and stroke could give much more.

[RustyBuzz]

A 127 should be capable of producing 13.5-14 without increasing the stroke length.

It could be the piston head, most likely the fit. Ideally the piston should slide forward under its own weight but stop dead when the transfer port is covered.

It could also be oversprung, maybe the best thing to do is ask Mr Macarri's advice on setup.

Regards

Richard

[CapitalBee]

I'm not sure what the Maccari spring can achieve with the 127. However, for mine, which is running on an Ox (suitably trimmed down) I'm getting 11.8fpe. I'm not sure the internal swept volume and stroke could give much more.

Just remembered the new FWB sport has an 18Joules option, which is 13.3fpe. You might get a better power reading with a different pellet.

[Phil Russell]

A 127 should be capable of producing 13.5-14 without increasing the stroke length.

Regards

Richard

Yes ... I agree, and the 124 (.177) can also exceed 12 ft lbs, not a lot, but exceed it.

I recently resealed a 124 that had lost its piston washer ... crumbled away. Fitted new piston washer, new breech seal but left the old spring as it looked OK ... nice result at 11.4 with AA Field.
Cheers, Phil

[NTSOG]

Thank you all for your responses.

I contacted Air Rifle HQ in the US and received this reply which may be of interest to FWB 124/127 owners besides me:

"Its too hard to answer that because the spring isn't the biggest influence on power.
the .177 124 was factory rated when new at 760-770 fps with an 8 gr pellet.
I have seen FWB 127's with a 14.3 gr do in these numbers 540-560-580-620 fps
Old guns have out around tubes and smaller breech seals- slower.
I have seen perfectly tuned specimens in the 40K SN range do 740 fps in .22 with that spring.
A guess would be 640-680 if its not under 10K SN

Elevation alone adds to it plus barrel tightness and so on."

The Serial Number for my rifle is 52xxx, hence I think I will install a new piston and breech seal for a start and see what happens.

Jim

Garibaldi, Victoria, Ballarat

[Shed tuner]

...and you certainly can get tighter and looser 'Sport cylinders. If your seal feels a bit loose, defo install a lighter one. One of my (4) Sports has a larger tube, and I ended up using a BSA supersport seal sized down a little to get a nice tight fit, as even a brand new (macarri) seal was too loose, making the gun shoot "slammy"...

[venoman]

The piston seal is a very common fault on them , often they shoot OK then the next time you shoot it the pellet dont leave the barrel. I stripped one last week with this problem, the piston seal had broken up all around the edge like it had been chewed by a mouse. I fitted it with a V-Mach kit it shoot very nice now , i have done a number of these over the years with this fault.