Idiots guide to classic airgun strips (pt 1)

[Phil Russell]

Having just completed another strip, service and rebuild of a Original 45 from 1980, I found a much simpler way of dealing with that beastly trigger safety spring. I thus offer a revised strip guide: I have left my original (very apt!) notes in post 58 in case people want to try a fiddly way...

REVISED MARCH 12 2016: BREECH SEAL: BS110 2.62cs

ADVICE: Make a slave pin 27mm long x 5mm diam to help remove end block.

A spring compressor is essential.

STOCK REMOVAL
2 screws front. Rear pin goes though the trigger. It is a bush and pin. Remove pin from left.

SPRING AND PISTON REMOVAL
Mount action in a compressor, barrel left and trigger unit upwards. To gain access to the spring and piston, the trigger does not need to be removed. Take up tension on the end block using a spacer on the underside, flat part of the safety.

Release and remove small spring on extreme left... simple.


Dismantle using the slave pin (recommended)
Use a suitable punch to push out the right hand pin securing the end block, but leave punch in place.
Use the slave pin to drive out the left cross pin holding the end block. The slave pin passes into the trigger block but sits clear of the sides of the cylinder. It serves to lock the safety spring in place in the trigger unit. Without the slave pin the safety spring springs down once the normal pin is removed. It is difficult to replace the pin without a fiddle!

Dismantle with no slave pin (not recommended)
Use a punch to drive out the lh pin, leave the punch in place. Drive out the rh pin, leave punch in place. Pull the punch from the lh hole. You will hear a click as the safety crinkle spring springs down … you can see the crinkle if you look through the pin hole.

To continue with either method:
Remove the punch from the right pin hole and allow the mainspring to push the end block out. The spring guide sits on a peg on the end block and may come out with the end block.

The spring preload is not excessive but take care. With the spring not under compression, remove spring.

To remove the piston, the cocking arm must be released. I released it at the breech block end by pushing the pin out. The pin may be held in place with a circlip, or maybe not. Remove cocking arm.
To remove the piston, the cocking shoe must be removed. The shoe is held in place by the piston sleeve so the sleeve must be pushed forward until the shoe falls off the end into the piston body. The piston can now be slid out. Retrieve the cocking shoe. There is a washer inside the sleeve, do not lose it.

The piston washer is leather.
Service as you wish.

Notes on a spring: The Original spring measured 34 coils at 3.12mm cs, 20.75 od and 14.44 id. I replaced with a Titan No.1 using 27 coils at 24.7mm long for .177. This meant cutting off c. 3 coils from the supplied spring. I tried fitting the full length spring but stopped when installation force became clearly excessive. Removal of 2 coils was still ott, a coil compressed was hovering on 12 so the compressed coil was removed to give 11.7 / 11.6. The spring length now just allowed the end block to locate in the action before taking up compression.

REASSEMBLY

This is basically a reverse of the above but these notes may help.
All the following was done with the action in the compressor.

Refitting the cocking shoe: A bit fiddly. I used a piece of 0.25mm ptfe sheet just inside the piston to hold the cocking shoe in the slot in the piston body. Now insert the piston into the action; it will be necessary to push the cocking shoe down a little to allow it to fit into the action and then show in the action cocking slot. Then use a piece of bent wire to hold the shoe in position while the ptfe sheet is removed and replaced by the piston sleeve … the sleeve will pass under the shoe and hold it in position. If not already done, replace the steel washer inside the sleeve, over the latch rod. With the spring, push the piston / sleeve to the bottom of the action.

Refit the cocking arm.

Add the spring guide, flat uppermost, and end block, making sure the end block is positioned correctly with the lugs over the flat of the guide.

Refit end block with slave pin.
Push the end block in using the compressor, making sure no block component on the left can foul the block as it enters the cylinder. Make sure the slave pin does not catch on the cylinder.
Continue compression until the slave pin appears in the lh hole in the cylinder. As a safety measure, add a punch through the rh hole but do not release spring compression. Using an original pin, carefully drive the slave pin out as the original pin is tapped home. Now add the rh pin. It is now possible to release spring compression. Replace the small spring on the lh side of the block. Check that the safety slides in and out with a distinct locating feeling as the safety spring moves on the lh cross pin.

Refit end block, no slave pin.
Compress end block until both pin holes are aligned. Use a punch to ensure free access is there for the rh pin .. inspection with a torch is useful. Add the rh pin.

Look into the hole for the lh pin. Note you can see a crinkle leaf spring across the hole. This part of the leaf spring needs to be pushed upwards i.e. towards the trigger blade to allow the lh pin to pass under it.
Using a small punch, insert the punch under the crinkle and push the crinkle upwards while introducing another punch from the other side of the action to hold the spring up. Repeat operation; eventually it will be possible to fit the lh pin in place.

If all fails it is most likely that the safety spring has slipped in its locating slot in the safety slide. There is no real alternative now: remove end block, pull safety out, relocate spring and try again.

Refit the spring on the left.

Refit action to stock: Simple but take care that the pin through the trigger has a clear path. This can be achieved by slightly moving the trigger and using a drift to align everything. Refit the stock pin and screws.
Cheers, Phil