Feinwerkbau Sport 124 & 127
Feinwerkbau Modell-124 Stripdown.
With thanks to Ian for the first set of pics and Rod for the trigger strip down on the yellow forum.
Here is a description in words thanks to Phil:
Useful information: Mainspring is 40 coils of 2.94mm wire, 14.8mm inner diameter, 20.8mm outer diameter. The removed length was 320mm; a new spring may measure c. 333mm. Breech seal is 3mm c/s, 16mm od, 10mm id.
A little time ago someone asked on the BBS for advice on stripping one of these sought after classics. I thought there was a guide on the Idiot’s Guide, but there was none. So here it is, a guide based on my very recent experience with a virtually new 124 (.177; the .22 is the 127). It was clear the rifle had had very little use. On first test shot, the pellet did not leave the barrel. Oh dear … classic symptom of a failed piston washer. Time to look:
Note this Guide does not include a trigger strip.
Important: You will need a spring compressor with a ‘long throw’ … there is considerable preload on the original spring. Other tools in addition to normal turnscrews would include a short (6”) plastic cable tie. I use one that you can release and use again. Small wooden block to fit on the end block so that the safety catch is not compressed when dismantling the rifle.
Remove foresight, two small screws. Put somewhere safe. Remove stock; two screws at front (do not lose the serrated washers) and the front screw in the trigger guard. Lift action out of stock and put stock safely to one side.
Place action in the compressor, preferably trigger uppermost and barrel to the left. Make sure it is secure. My compressor lets me clamp the cylinder to the compressor bed to avoid undue movement. Place wooden block in position so that when you start to remove the end block, there is no pressure on the safety slide. Just take up the pressure on the end block. Now start to undo the end block securing bolt in front of the trigger. I used a 7/16” af spanner (I think this is 11mm) as it was to hand and fitted perfectly. It may help to just nip the end block up as you release tension on the bolt.
Remove bolt and then slowly unwind the compressor about ½”. Now take the cable tie and wrap it around the end block, passing under the safety slide, and secure it. This holds the safety slide in place. This is not absolutely necessary but does help and it prevents the safety slide and sear spring from pinging away as the end block (trigger block) is released. Continue unwinding the compressor until the trigger block and then the spring become free. The end block and spring simply lift away. A spring guide is part of the trigger block.
To access the piston it is necessary to release the cocking arm. Undo and remove the small screw on the breech pivot bolt followed by the pivot bolt itself. The barrel assembly and cocking arm can now be released from the breech jaws and the cocking arm released from the ‘shoe’ in the cocking slot. Note there will be a domed shim washer fitted in a recess in the breech jaws, right hand side; do not lose it.
To remove the piston, slide it towards the end of the cylinder where the cocking slot is much wider. It is now possible to remove the cocking shoe, after which the piston just slides out. My piston head was indeed disintegrated; bits were left in the cylinder and I had to dig the remnants out of the end of the piston. A new head is a push fit into the end of the piston.
After cleaning all parts, reassembly is a reverse of the above: Lubricate the piston and place in the cylinder, slide piston in so that you can fit the shoe in the slot … the cocking arm contact point towards the trigger block end.
It is tempting to continue assembly of the spring and trigger block to the cylinder before fitting the barrel assembly. Do not do so.. the pivot bolt cannot be fitted this way. So: fit cocking arm end into the shoe and slot the well greased breech jaws plus shim washer into the cylinder jaws and screw in the pivot bolt. I found it easier to do this before putting the action back into the compressor. With the barrel assembly fitted add the lubricated spring and place assembly in the compressor.
Add the trigger block to the spring, trigger uppermost and add the wooden block again, making sure it does not press on the safety slide. Begin to wind the trigger block in, making sure that the safety slide enters the cylinder in the process. Continue to compress the spring until the trigger block has just over ½” to go and then remove the cable tie. The trigger should be central to the slot in the cylinder. Continue compression until the securing bolt holes line up and add the bolt. It may be necessary to jiggle the holes to enable the bolt threads to nip. Do not force the bolt; when correctly aligned the bolt will go in virtually under finger pressure. Tighten bolt. Release pressure on the compressor, remove action, refit stock and sights. Job done.
After this service the rifle was consistent at 11.4 ft lbs with AA Field.
Feinwerkbau 127 (boxed)
With thanks to Tim Dyson of http://www.timdysonairguns.co.uk/