Part 2, the rebuild:
ORIGINAL MODEL 50 REBUILD.
Nothing to fear really, but a bit fiddly at times.
Put action in the compressor, barrel left, trigger slot uppermost.
Replace piston, mainspring and spring guide. Make sure the piston is positioned with the underlever cocking arm slot uppermost.
Insert the large sleeve into the cylinder about 2cm, the cut out uppermost and pointing towards the stock end of the action.
Assemble the sleeve and 3 bearings ... a dab of grease in the bearing holes keeps them in place. Bearings fit in the holes from the outside. Insert this sleeve into the action, with the ‘join’ uppermost. Locate it against the piston sleeve. The spring and prod needs to be fitted but I found it easier to do this later.
With the socket against the 15mm sleeve, compress the sleeve into the action. This does not automatically move the outer sleeve in so I found it best to carefully move the outer sleeve in by hand (it is not under pressure).
Push the small sleeve in until to cross pin holes are aligned.
It is now time to fit the prod and spring.
I used a short length of cycle spoke to help ... put it through the left cross pin hole and release tension on the compressor. I expect the spoke will bend a bit at this point.
Now turn the action upside down so that the trigger slot points down.
Take the prod and spring and insert the spring over the top edge of the inner sleeve. You may need to lever the sleeve down a bit (hence the freedom to do this give by the spoke) to get it started. Feed spring and prod in as far as they will go. The raised lip of the prod now needs locating behind the rim of the inner sleeve. Push inner sleeve down while pushing the prod in. It will click into place.
Tension the main spring again using the socket. I now insert a drift, or if possible, the correct cross pin through the first hole before removing the spoke. If it is not possible to fit the first cross pin because of slight misalignment, use a suitable drift and then remove spoke and add another drift. It should now be possible to jiggle the alignment Ok by adjusting tension on the mainspring. Fit front cross pin, and then the second pin. You can release tension on the socket.
Turn action again so that the trigger slot is uppermost.
Fit the trigger by replacing its pin but without the spring.
The spring now needs to be fitted. A bit fiddly as it is quite strong.
With trigger fitted, use a blunt screwdriver to push the ‘outer sleeve’ down the side of the trigger so that the trigger engages. This gives a little more room to add the spring.
Locate spring on the nib on the action and compress spring so that it fits over the nib on the trigger blade. This is fiddly. I find it best to use a flat blade screwdriver, using the flat of the blade to push on the spring while I then nudge the spring into the trigger housing. Take care and all will be well.
That’s it .. hard part over.
All that remains is to replace the loading tap ... remember the little ball that sits on the spring in the tap. Replace the barrel cover bit and then locate the underlever into the action before feeding the stock over the lever. Refit the round nut over the underlever catch and refit the through bolt on the stock, making sure it passes through the underlever. Refit the rigger guard bolt. Refit sights.
As I hope you will see, the ball bearing trigger is not too difficult. It is possible to fit it as a complete unit with the prod and spring assembled but it is more fiddly. If you want to do this, assemble the outer sleeve, inner sleeve and the spring and prod as a unit before insering into the cylinder. You then need to hold the prod and spring firmly in place as you wind the sleeve unit into the cylinder. It is possible with care.
When I first stripped a model 50, I had access to ‘Air Rifle and air piston maintenance and repair’ by Q Cobham ISBN-10 0-9553131-0-4 which gave me confidence to proceed. I supplemented my actions with more notes, upon which this account is based.