Idiots guide to classic airgun strips (pt 1)

[Phil Russell]

Not sure if this is a collectable yet, but here are some notes I made after a strip and clean of an auction find: Sorry, no pictures. It can help to look at the Chambers parts diagram.
NOTES ON DISMANTLING AND REBUILD OF ORIGINAL 45

STOCK REMOVAL
2 screws front. Rear pin goes though the trigger. On our model it looks like a bolt with allen heads as the bushes the pin goes into are a bit mangled. But it is a pin that is drifted out.

SPRING AND PISTON REMOVAL
To gain access to the spring and piston, the trigger must be removed. This is best done with rifle secured and trigger pointing up.
With the barrel to your left:
Remove circlip holding the trigger unit to the end block (2nd circlip from left ... quite clear)
Release and remove spring on extreme left... simple
Lift trigger unit away

The spring preload is not excessive but I found it easier to use a spring compressor.
Use compressor to hold end block in place ... in effect this means holding against the safety block. I used a piece of wood to get a good contact on the straight edge.
Push out the two pins holding the block in position. This releases the safety leaf spring, but do not worry, it will not ping away but remain in the safety slide.
Release spring tension.
The end block with safety slide comes out, with the spring guide and spring. Remove the parts, noting which way round the end block goes in relation to the spring guide. The safety slide comes away from the spring guide. Do not lose the leaf 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 is held in place with a circlip but this was missing on our rifle. Remove cocking arm.
The piston can be slid out.
The piston has a sleeve. If you remove the sleeve, take care that you do not lose the cocking shoe (about 2cm long x 6mm wide) as it is held in place on the piston by the sleeve.

Service as you wish.

REASSEMBLY

This is basically a reverse of the above but these notes may help.

Refitting the cocking shoe: A bit fiddly. I found it best to insert the piston body into the cylinder (not fully!), hold rifle upside down above my head, then add the cocking shoe (right way round) and jiggle it so that it lay in position in the slot of the piston. Then, still with the rifle upside down, add the piston sleeve. With care it is possible to slide the sleeve into the piston so that it goes over the cocking shoe and hold it in place.

Refitting piston and end block: With piston shoe fixed, replace rifle in compressor, barrel to the left and trigger housing such that the trigger will point up, and add the spring. At this point I refitted the cocking arm. Add spring.
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. Add the safety slide, making sure the slide fits snugly in the guide and that the safety is the right way up (leaf spring slot pointing up) Compress spring to bring the two pin slots into alignment. Take care when doing this that the flat on the spring guide stays true to the end block. I used a punch to hold and align the left pin holes. Insert pin in the left hole.
Now you can add the leaf spring for the safety. I used a punch to hold the legs of the spring apart, then introduced the spring such that the legs went either side of the pin just fitted. The spring ‘crinkle’ should be pointing up. The spring is now held by just the ‘crinkle’ on its left.
Release the compressor tension. Carefully pull the safety slide out to allow the rest of the leaf spring to be pushed down into the safety slot. Push safety in. It is now possible to fit the second pin through the block, with the pin passing through the leaf spring. This can be a little fiddly. Do not hammer it through. I found it easier to use a torch to see how the pin was aligning with the holes and to use the spring compressor to just add or release a little tension such that the pin slides easily into place.
Release spring compressor and check that the safety slide moves easily in and out.

Refitting trigger: Not a problem but a bit fiddly to get the pin in place. Slide trigger unit into position in the end block and add the pin. I used a drift to first locate the pin holes then carefully pushed the pin into place. You may need to jiggle the position of the trigger unit to get the pin to locate.
Refit circlip. Refit the spring on the left of trigger unit.

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.

Job done.
Cheers, Phil

[Prewar]

Unscrew 2 trigger guard screws

http://i133.photobucket.com/albums/q...ff/BBS/012.jpg

Pull trigger back and turn stock anti clockwise from cylinder to unscrew

http://i133.photobucket.com/albums/q...ff/BBS/013.jpg

You can now access the mainspring

Unscrew bolt to remove cocking arm

http://i133.photobucket.com/albums/q...ff/BBS/014.jpg

remove cocking arm from cocking slot

http://i133.photobucket.com/albums/q...ff/BBS/015.jpg

You can now remove the piston assembly

[ggggr]

I dug the Merlin out of a box. I intended to strip, varnish and spray it with placticote when I move, but the Idiots guide got the better of me. I dont really know how to describe the strip and the Chambers page isnt much use but here goes.Take out loading tap and put in safe place!
Undo and remove front two stock screws and the one at the rear of the trigger guard (its like a woodscrew as it goes into plastic end cap). As you lift action out of stock, the sliding plate attached to the cocking lever will slide backwards until action can be lifted out. On mine the trigger guard came up and out with the gun, but it may well remain in place. The end cap slides out of the rear of cylinder with the trigger spring (note how the spring sits in recess in plastic). The trigger then slides out of cylinder. If you remove the cocking lever pivot pin (WATCH OUT FOR THE SPRING THAT SITS IN THE MIDDLE) then all the cocking lever stuff can be removed. THere is a pointy bit of thin steel that is the safety, which sits between the cocking lever, with the pointy bit facing forwards. There didnt seem any point in stripping that further so I just put a bit of GN paste and LT2 round it. To remove the mainspring and piston, you have to remove the funny spring clip at the rear of the cylinder that this gun has instead of a pin. GO TO NEXT POST.

[ggggr]

I assume there must be a special tool to do this and a big lump of round bar might help. A spare pair of helping hands would make it easier as well. I pushed down on the clip ans then flicked the bits that locate in the slots on the side of the cylinder out with a small screwdriver. Once out, release pressure and remove clip,gide,spring and piston. You will see a small serrated flatbar pin at the front of the piston. Tap this out with a punch and piston head will come off and you can change buffer and washer. (this piston head set up is a bit like the Mercury with flatbar instead of a round pin BUT the buffer material seems better than the later neoprene material). Clean and lube. Replace piston head and secure with pin. Replace piston, mainspring and guide and try to replace the spring clip. I tried to just close it slightly so it would enter cylinder and open up once in place. Replace cocking linkage and safety (remembering the spring in the middle). The safety is a bit of thin steel with a pointy end and a flat end. It sits with the pointy bit upwards and faces the front of the gun The spring seems to sit best with the open ends to the top and the closed end to the bottom. I am fairly sure you can leave the safety plate out and just use the spring (I'm sure I used mine like that before fitting the safety) .Replace trigger in cylinder and then put trigger spring into endcap and slide into cylinder ensuring spring locates behind trigger. I put the trigger guard into the stock and then slid the action in. Tighten the 3 scews and replace loading tap. This gun had a lot of paint in the cylinder and responded really well to a clean and lube. It is quite punchy for its size and a fun plinker.

UPDATE---I've seen 4 MK2 versions of these now and 3 different types of trigger spring. One of them has a double hook coil spring that hooks onto the safety sear spring and a hole at the front of the trigger. The other 2 have either a flat or round wire spring that goes behind the trigger. I've also seen both types of trigger guard on these.
Also I forgot to mention about the transporter (the tap thing) washer, base and spring (little bent washer). The base is a round metal thing with a spiggot on it that the washer sites on and they sit in the cylinder end along with the transporter spring. If you are replacing these, the transporter spring goes into the hole at the end of the cylinder with the point end facing outwards and then the metal side of the transporter base goes on top of that with the washer facing the transporter (tap).

[ggggr]

Ive seen 4 paratroopers and they are all a bit different in regards to screw sizes,screw positioning,etc. This guide should do for all bar the one with the Gamo type slot in trigger unit (think late Bsa Meteor, CF20 etc). It should also do for the repeater.
Remove rearsight and then all plastic panels and put somewhere safe. Undo the two small scews at the fore end underside of frame. Undo the small keeper screw (if it has one) that locates on big screw at rear of cylinder/frame. Remove large screw. Action should now lift out. If you want to play with the trigger,there is usually one posidrive screw at rear under side of frame and one visable through hole in trigger guard. If you undo these then the trigger unit should lift from frame. Ive not stripped one of these right down but there seems little to go wrong other than a sear wearing or its spring breaking. If this is the case then knock out the pin and replace the spring and locate it on the little tang on the LHS of the housing. I will assume you will just clean and lube it and place back in the frame. If you want to play with the adjuster screws (front and back of the 3 together behind trigger, middle one is the lock screw that needs loosening before adjustment as it pushes on a small spring clip against the other two screws) GO TO NEXT POST.

[ggggr]

If you have the reapeater version, you can take the brackets off the top of the cylinder now( two screws in each plastic bracket--Front one holds the loading plate). Cocking arm should come out of slot now. To remove barrel,undo lock nut on RHS (some models dont have this) and then tap out pivot screw----THESE ARE HARD TO UNDO so use a good screwdriver---barrel will come out with 2 plastic washers. If you want to get to barrel plunger and spring, you need to knock out the barrel pivot sleeve to do it---Do it, lube and replace. Hold cylinder with breech jaws down and push on end cap and remove cylinder end pin--release pressure and remove guide, mainspring and piston. Ive seen these with a screw on piston washer or a rivetted version. A meteor mainspring with 2-4 coils cut off will do the job if you cant get proper mainspring.Bear in mind the biggr the spring, the more pressure on the sear and these are getting hard to find now. Replace piston,mainspring and guide, push on end cap and replace cylinder end pin. Put breech in jaws and locate pivot pin (easier to do with barrel broken) and then tap it through and replace lock nut. I use a screwdriver with a gap groung into it for these jobs. GO TO NEXT POST

[ggggr]

Leave the barrel broken and dont locate cocking arm yet. If you have a repeater, there is a small "O" ring on the cylinder that seals that side of the loading plate---check its there and in good nick. I made one up out of leather and it seems to be working ok. Replace the repeaters brackets and the loading plate on the top of the cylinder. Once the front bracket and loading plate are in place, then you can close the barrel and locate the cocking arm. Replace action in frame, replace two front screws and the large rear one (and its lock screw if it has one--if the hole is there but no screw, I think its 3 0r 4mm---I got one from local hardware shop and cut it to length). Replace plastic and sight.
Id hate to have to order spares for these because there are so many little variations. If you have the repeater and the magazine and rear bracket are missing, you still need the front one because of the loading plate. The barrel is different to the normal rifle. AS I found out, DONT BUY A BOX OF BITS-- the mk1 and 2 frames and cylinders are diffreent as is the one with the Gamo type slot in trigger. Keep the power down and you will have a fun, accurate plinker to put a smile on your face for years to come.

[Citizen33]

I dug the Merlin out of a box. I intended to strip, varnish and spray it with placticote when I move, but the Idiots guide got the better of me. I dont really know how to describe the strip and the Chambers page isnt much use but here goes.Take out loading tap and put in safe place!
Undo and remove front two stock screws and the one at the rear of the trigger guard (its like a woodscrew as it goes into plastic end cap). As you lift action out of stock, the sliding plate attached to the cocking lever will slide backwards until action can be lifted out. On mine the trigger guard came up and out with the gun, but it may well remain in place. The end cap slides out of the rear of cylinder with the trigger spring (note how the spring sits in recess in plastic). The trigger then slides out of cylinder. If you remove the cocking lever pivot pin (WATCH OUT FOR THE SPRING THAT SITS IN THE MIDDLE) then all the cocking lever stuff can be removed. There didnt seem any point in stripping that further so I just put a bit of GN paste and LT2 round it. To remove the mainspring and piston, you have to remove the funny spring clip at the rear of the cylinder that this gun has instead of a pin. GO TO NEXT POST.

Thanks to Ggggr for his useful posts on the Merlin. Being more stupid than the average idiot, there were a couple of points that weren't clear to me and I thought more detail would help.

As you lift the action away from the stock one thing to be aware of is that the lever axis pin may be loose enough to drop out if you turn the assembly sideways, causing the safety sear and spring to fall out and leaving you unsure of their orientation (this is what happened with mine). The other thing is that once the end cap screw going through the trigger guard is removed, and you lift the action away from the stock the plastic end cap may pop out, letting the trigger spring fall out, and again leaving you in doubt about the relative positions. My advice would be to slowly lift the action a couple of inches from the stock and examine the positioning of these parts before you try to get the lever and sliding plate out.

The safety sear sits with the closed side towards the action and the long thin spur towards the barrel. The end of the spring with twin prongs sits inside the closed part of the sear and the end with a loop is tensioned against the trigger guard, which you will have to position carefully on top of the spring when you re-assemble. Putting a small hook through the looped end of the spring may make re-assembly easier.

The long end of the trigger spring sits behind the trigger (facing down and parallel), while the short end with bend is positioned in the square hole on the front of the plastic end cap.

I have made pdf diagrams of both assemblies, and also have a very helpful collection of photos from member Isobar (whose help was crucial in letting me fix my gun). I'm happy to forward these via pm, or if a moderator wants to add them to the thread will supply on request. I do not appear to have posting rights for images. As Grrrr noted, the diagram on Chambers' website isn't very helpful and doesn't show the safety sear.

[ggggr]

The ASI/Gamo Center pistol is an underlever cocking pistol with a plastic plate/loading tap that flips out of the side. It is a better version of the Gamo Falcon (which apparently came later at a cheaper price) but has no safety catch. The Falcon (if my memory is correct) had a crappy plastic lever located by a small spring and a bb.
The Falcon also had a plastic frame which made it seem very crappy, almost like an RO72
The Center has a fairly decent die cast frame. You can also adjust the angle of the grips by undoing the screw on the underside of the pistol grip and swiveling the grip into place before tightening the screw again. The trigger is adjustable via the smaller of the 2 screws at the back of the trigger guard, although you have to undo the larger one a little first as it bears on a piece of spring steel that locks the smaller screw into place.
The example of the gun I have had a crude homemade rearsight and someone had fitted a .22 barrel and drilled to loading tap to suit.
Ok--here we go. Remove the rearsight if you want. To make things easier, undo the screw on the underside of the pistol grip and then remove the upper of the grip screws. This will enable you to remove all the pistol grip (for ease). The frame is fastened to the cylinder by 3 screws, one at the back and 2 at the front. Undo these and remove the frame.
You can knock out the cocking arm pivot pin and remove that if you want. If you want to remove the loading tap, the is a screw at the front of the breech block, next to the barrel. If you are doing a fullish strip down you may want to do this to change the breech seals or the O ring on the transfer port insert (More later). Put pressure on the endcap and remove the cylinder end pin and release pressure to remove the endcap/guide, mainspring and then piston. The piston washer is a leather one, with a plastic buffer, held on by a crosshead screw. With the guide,spring and piston out, if you shine a torch down the cylinder you will see the transfer port insert. If you wish to remove this (it has a small O ring on it to seal it) then you will have to undo the grubscrew at the front underside of the cylinder. This locates in a groove on the insert. With the screwout, you should be able to use a small rod or something to push it into the cylinder. The O ring that seals the breech will probably remain in place. There is also a seal on the barrel side as well if you want to change that.
Clean and lube your bits and go to pt2.

[ggggr]

Assuming you have removed the transfer port insert for a look and maybe fitting a new O ring on it, you will want to get it back into position. I managed to drop it into the cylinder, get it into place and then push it with a dowel. I fitted the piston, mainspring and guide before refitting the loading tap, but I think doing the tap first is a better idea as it might be tight if you have fitted new breech seals. Locate the loading tap and locate and tighten its pivot screw. If the tap is tight, due to new seals, then you can wangle the transfer port insert a little. Once you are happy with it, replace its locating grub screw on the underside of the cylinder. Replace your piston, mainspring and guide/endcap. Put some pressure on the endcap and push the cylinder pin through to locate it. Replace the cocking lever and locate the cocking arm into the cylinder and then put the cylinder onto the diecast frame and replace the 3 screws that hold it. Replace your grips and replace the top grip screw. Swing the grips to the angle you want and then tighten the screw on the underside of the pistol grip. Replace your rearsight.

I have not had a chance to try the pistol since the strip and I guess it will not be too accurate with the crude rearsight. It does however seem a fairly well made pistol. I have not checked the spares situation and did not remove the trigger components, but did notice a little wear on the pins, where the cocking arm had rubbed.

[ggggr]

This one must be a fairly late one. It has the "saddle" rear sight, a cast foresight, 2 piece cocking arm and a trigger unit. The one I got was missing the spring guide, mainspring and cylinder end cap. The cocking arm was damaged at the front, which I guess was caused by brute force trying to get it out of the cylinder The pins and screws on the trigger unit had corrosion, so although I managed to get the pins out and lubricate the sear and trigger, I cannot adjust the screws
If you want to remove the foresight, you will have to take the protector off to get to the screw that holds the sight on. To remove the rearsight, knock out the split pin that secure the sight to the breech block, remove the elevation wheel and the sight will lift off. Watch out for the little spring underneath it.
Undo the 2 front stock screws and the front trigger guard screw and the action will lift out of the stock. The cocking arm will lift out of the cylinder. You can remove the pivot pin and lubricate the arm,pin and slot if you want. Knock out the barrel pivot pin. If you want to remove the barrel plunger and its spring, you need to push the plunger in and undo the little grub screw on the LHS of the block. Once you have lubricated it, replace it. (I usually use a small piece of wood to push the plunger instead of just my thumb).
Remove the cylinder end cap and the cylinder end pin and the trigger unit will come out. I would suggest getting some penetrating oil on all the trigger bits as they do seem to suffer from corrosion.
A steel ring that located the front of the trigger unit in the cylinder should also come out of the cylinder now. Using the forked bit of tube often mentioned on this thread, keep pressure on the Plug (for want of a better word) in the cylinder and undo the nut that locates it. Release pressure and the plug, guide and mainspring will come out. The piston can be removed now as well.
The piston washer is held by a forked nut. I didn't attempt to undo the nut as the piston washer was in good condition.
Clean up the bits, lubricate them and go to part 2.

[ggggr]

Unscrew 2 trigger guard screws

http://i133.photobucket.com/albums/q...ff/BBS/012.jpg

Pull trigger back and turn stock anti clockwise from cylinder to unscrew

http://i133.photobucket.com/albums/q...ff/BBS/013.jpg

You can now access the mainspring

Unscrew bolt to remove cocking arm

http://i133.photobucket.com/albums/q...ff/BBS/014.jpg

remove cocking arm from cocking slot

http://i133.photobucket.com/albums/q...ff/BBS/015.jpg

You can now remove the piston assembly

BSA Pre War Break Barrel Strip.

As the pics have gone from this and I have now bought one of these guns, I thought I would add a little to this post.
Unscrew the 2 trigger guard screws and remove the trigger guard. Unscrew the barrel pivot screw and lift the cocking arm out of the slot in the cylinder to free the barrel and breech block. You can unscrew and lube the cocking arm pivot screw now if you want. There is a little pin in the breech block, that retains the barrel plunger. You can drift this out and remove/clean and lube the barrel plunger and spring. Sometimes a little block of wood helps for pushing plungers back in far enough to relocate the pin.
Unscrew the trigger block, keeping tension to stop it flying as it clears the cylinder. The mainspring and piston should now come out. The mainspring on mine had a rough end so I heated it and flatted it. I think the piston washer should be a normal leather cup washer set up with a buffer and the dimpled steel washer, held by a screw. Unfortunately, the buffer washer was missing on mine and 5 small steel washers had been used instead. This meant that the piston had been slamming into the end of the cylinder and also damaged the head of the screw that holds the washer on. The piston rod should unscrew once you have undone the little lock screw, but as mine looked fine I just cleaned the piston up. I made up a buffer washer and found a dimpled steel washer to complete the piston washer set up. Before I put the gun back together, I undid the trigger pivot screw and removed the trigger and trigger spring for cleaning and lubing. I also cleaned out the trigger housing. I find this is worth doing on the old stuff as you might have grease that could be somewhere between 70 and 100 years old!. The trigger spring is located in a hole in the trigger housing and the trigger slid back in and lined up and the pivot screw replaced.
Refit your piston and mainspring and screw the trigger block back on. When It is located, replace the trigger guard and the 2 screws. Before you replace the barrel, it is worth checking the breech seal washer as these are often old/worn and are often the cause of low power.
Locate the cocking arm in the cylinder and locate the breech block in and barrel in the breech jaws. replace the pivot pin.

This was very low in power and I suspected the breech seal, which I had left in for now just to see how much difference it would make. Once the new seal was made up and put in, the gun shot quite well. I would say it is quite a well made little plinker.

[ggggr]

I have just found this on Chambers Website, which might help.https://www.gunspares.co.uk/products/24464/G71/ . I bought this recently to have a look at one. Unfortunately, the safety catch is missing although the gubbins are there on the inside. This came with a missing medallion, none original stock screws and the stock had broken at the fore end at some point and been repaired. This is more or less a G 78/79 with a different trigger and a barrel sleeve. The sleeve on mine will turn (I am guessing it shouldn't) so it either needs the foresight sliding back to hold it tighter or a washer/shim behind the sight. The sleeve slides over the barrel and is held in place by the foresight and there is a threaded piece at the end of the barrel that screws onto the barrel.

Undo the front stock screws and the rear one at the front of the trigger guard. The action should lift out of the stock, and leave behind a small cranked bit of metal that holds the trigger adjusting screw. It is located by the front trigger guard screw so if you have fully removed the screw there is a chance it could fall out of the stock. Lift the cocking arm out of the cylinder and undo the barrel pivot screw and remove the barrel/breech block. If you want you can undo the tiny screw on the LHS of the breech block and remover the barrel plunger and spring for lubing. I usually push the plunger with a small block of wood when removing or replacing it. Once you have lubed it, replace the spring and plunger back in the block and tighten the screw.
I am not sure how the safety attaches to the gubbins, but assume it would just hook on. The safety is just a simply rocking bar that stops the trigger from moving. It is located on a bar in the cylinder sleeve and centralised by a spacer and a spring. It does not need removing for the strip.
Put some weight onto the sleeve and you can remove the trigger pin/cylinder pin. Once it is removed, slowly release pressure and remover the cylinder sleeve, guide, mainspring and piston.
The piston washer is leather, with a fibre spacer below it and is held in place by a screw, ( which I prefer), rather than a threaded nut, like some of the Milbros.
As the screw was tight and the washer in good condition, I did not remove it. The mainspring in mine was something that someone had fitted and left the end rough, so I flatted the last coil and cleaned it up.
Go to pt 2

[ggggr]

Replace the piston, mainspring and guide into the cylinder and then the cylinder sleeve. Compress the spring and locate the sleeve with the cylinder pin/trigger pin or a slave pin/punch.
The aluminium trigger is pretty much the same idea as the early triggers, with the 3 floating bit of sear. It is a bar steward to get the trigger pin through the all the bits. On older German Dianas, they had 2 pins, 1 to hold the sleeve and one for the trigger, which made it easier to fit. This is one reason I do not like working on the Milbro versions. If you are lucky, you may get the pin through first time or you may be unlucky and spend 30 minutes swearing at it. I made up a small aluminium slave pin to put through the trigger and sears first to give me a fighting chance of getting the pin through and it went in with a bit off jiggling.
Replace the barrel and locate the cocking arm in the cocking slot of the cylinder and replace the cylinder end cap and drop the action into the stock (remembering to replace the trigger adjust bit if you removed it from the stock earlier). Replace the stock screws.

This is like most Milbros in that it should be better. The addition of a 2nd pin for the cylinder sleeve/ trigger would help. I prefer the simple idea of the safety mechanism on this to the G25/27 etc set up, but guess the actual catch was very flimsy. The front stock screw holes do not seem to be deep enough for my liking, and maybe the original screws came loose and resulted in the stock breaking. I only fired 5 shots with it as it was getting dark, but it does seem accurate at short range. It was dieseling a little but this is normal when you have cleaned a gun out and used modern lubes as the old stuff take a while to burn off.

[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