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Thread: Idiots guide to classic airgun strips (pt 1)

  1. #166
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    Pre war Diana 25 strip (full stock) pt 2

    Put the piston,mainspring and guide into the cylinder and then the cylinder sleeve. Make sure it is the right way round. Compress the spring and use a slave peg to locate and hold the sleeve. Keeping pressure on, you should be able to locate the cylinder screw/trigger pivot screw and push it through the trigger. Once located, replace the lock nut. Replace the trigger spring, making sure one end is on the TANG of the cylinder sleeve and the other is on its PIP on the trigger. Screw on cylinder end cap.
    Locate breech block shims and place barrel in the jaws. Locate and screw home the pivot screw and the lock screw.
    Locate cocking arm and replace its pivot and keeper screw.
    Refit action in stock and replace the stock screws.

    I think this is a nice little rifle. I was surprised at how good the internals were on mine. The piston washer was in good condition and the piston head screw retaining peg had no witness marks round it. I had a quick plink and it is accurate enough. The trigger has a long pull but is pleasant to use.

    It is interesting to note that the German post war 25's had one pin to hold the sleeve and one to act as a trigger pivot. The British version just had one pin to do both jobs.
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    Webley Service MKII

    I just had a need to strip one of these to correct a couple of faults and was surprised we had not covered this classic yet. So here it is: really a very easy job but maybe daunting because the action looks complicated.
    WEBLEY SERVICE MKII

    This is a third series rifle, No. S9304 in .22 flavour. The strip was carried out in order to discover why the trigger was very light and to change the mainspring as power was a little down. The strip includes help on stripping the basic components to access the piston and mainspring,but does not deal with the front block with the barrel locking mechanism.

    To begin the strip, remove the barrel. Remove the butt plate and then the stock by undoing the large screw bolt inside the end of the stock . The action is now a very handy size. With the trigger uppermost. undo the large bolt retaining screw at the front of the trigger housing and place it safe as it is easily lost. There is a thin screw that passes through the rear of the trigger guard/housing. Remove it but try and keep the trigger housing against the action; not crucial though. Now release the large bolt at the front and lift away the trigger housing complete with trigger and a long sear. Note the small spring in the sear. Do not remove it if it is firm but make sure you do not lose it. There is no need to remove the trigger or sear unless they need replacing.

    Now to remove the cocking arm mechanism. It pivots on a pin, about 6mm diameter, at the front of the action. A small grub screw in the end of the action needs to be removed before you can drift this pin out. Put the grub screw safe and drift the pin out ... do not worry, it does not retain the mainspring. Remove the cocking linkage mechanism by unhooking it from the slot in the piston. There is no need to remove the interceptor sear (= anti-bear trap sear) on top of the action. This pops down to hold the piston back when the rifle is cocked and the barrel is ‘broken’. When the barrel is located against the action the barrel pushes the interceptor sear out of the way.

    The mainspring and piston are held in by the threaded end block. To remove this I mounted the cylinder in a padded vice and carefully unscrewed the end block; starting the movement by using the flat side of a spanner. I realised that a small home-made tool would work wonders here ... a simple piece of wood 15mm x 18mm x about 10cm allowed me to unscrew the block easily. But I still wore a leather glove as I had no idea what preload was present. In fact, preload was not much and the end block had a captive spring guide so controlling the spring release was easy. The spring and end block simply lift away. The piston can be slid out but you need to depress the interceptor sear to allow the piston to pass it.

    The spring was 32 coils at 3.1mm wire diameter. It was clear that the spring had seen better days as one end had severely compressed coils. A standard Airsporter spring was a perfect fit but on my spring was a coil too long so I trimmed it back to match the original.

    The rebuild was basically a reverse of the strip. I removed and cleaned the piston; the piston ring was fine. As recommended, I relubed the ring with a little motor oil before refitting. Make sure the piston passes the interceptor sear. I now added the trigger housing. I realised that my light trigger issue had been due to the trigger housing not being bolted tight against the action. In part this was due to the location of the small locking screw because in its original position it allowed a little play in the main bolt. So I fitted a thin washer under the bolt head and the bolt now tightened nicely with the retaining screw perfectly aligned. The action was now again mounted in the padded vice. I lightly greased the spring before adding the end block and spring guide. There was about 20mm more preload with the new spring. I used my wooden tool in the end of the end block and compressed the spring and turned the tool to engage the threads. Not too difficult at all but I still wore a thick leather glove just in case it slipped. Screw the end block all the way in until the slots and the holes for the pivot pin align. Add the cocking linkage and feed the barrel pivot into the end block slot. Replace the pivot pin and add the retaining grub screw.

    Replace stock and butt plate. Slide barrel back into its housing. Result: good trigger action again and increased performance at a little over 520fps. A couple of shots dieseled to begin with but the rifle soon settled down.

    Tip: If you think the barrel is not seating properly, a new breech seal can be easily made from a red fibre washer. The barrel lock bolt handle pulls the barrel firmly against the breech seal.

    Cheers, Phil

  3. #168
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    Quote Originally Posted by Prewar View Post
    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.
    Last edited by ggggr; 02-07-2015 at 12:44 PM.
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  4. #169
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    Theoben Fenman HE 1997 stripdown guide

    Just a bit of basic info for anyone who hasn't stripped one of these gas ram riles. Probably one of the easiest break barrel rifles to strip and work on as once the gas ram has been fully depressurised, there is nothing under tension.
    Mine is a 1997 model serial number TB11176. The rear face of the cylinder is flat ( no external O ring showing. It has a slotted plug covering the schrader and a grubscrew directly below ( unlike a HW90).
    Ensure you have the means to recharge the ram and have a chrono to check after reassembly.

    This is meant for info only and any work carried out is at the risk of the person carrying out the work. Other variants of this rifle may have different components inside

    1 ensure rifle is uncocked and unloaded.
    2 remove the 2 forend bolts and the forward bolt from the trigger guard and remove the stock.
    3 remove the slotted plug that covers the schrader valve ( this has an o ring on the threads to seal it)
    4 using a 3mm punch or similar and something not too heavy to tap it with, gently tap the schrader valve a number of times until all the air is expelled. When you think all the air is out , depress by hand with the punch to make sure.
    5 carefully break the barrel just to take the tension off the cocking linkage. The cocking link pin will be lightly narrower on one side of the breech. Drift the pin out with a suitable punch tapping the narrower end of the pin. when removed from the breech, there is a ptfe or similar washer between the arms of the cocking linkage. catch this and dont lose it. swing the cocking link away from the breech rotate the link 90 degrees and lift the cocking shoe from the slot o=in the cylinder.
    6 remove the grub screw from the rear face of the cylinder with an appropriate hex driver ( this retains the cross pin that goes through the rear of the dummy piston.
    7 gently tap the large pin through the rear of the clinder and keep safe.
    8 using a punch or similar push the piston down the cocking slot. it will meet solid resistance and at this point, the sear at the rear of thetrigger needs to be lifted to allow the piston to pass it and be removed. ( same applies on reassembly)
    9 remove dummy piston rod
    10 remove wire retaining clip
    withdraw ( by tapping the piston on some wood or similar) the seal unit. This may catch a little at the groove that the wire clip sits in but you should be able to get it out far enough to gently grip it with some pliers or similar.
    11 remove any other parts that may still be in the piston. in my case there was a black oil scraper/seal and the inertia weight. The inertia weight can be difficult to remove. a magnet may be handy.
    12 inspect the piston crown. any deformation or brown colouring may indicate this has been over pressured and is in need of replacement.
    13 clean, relube and renew all seals. be very careful as the seal unit also has some oil scraper rings fitted inside it.
    14 reassembly is the exact reverse of the strip.

    Just a few futher notes. If you find / suspect a new schrader valve itself is needed please be aware that depending on the age of your rifle, the dummy piston may need retapping to suit the threads of the new schrader valve. Luckily mine was ok.
    After conversations with the lads at impact it appears that these rifles were subject to constant research and development and many things were tried and the innards may differ between rifles. Seal units may have been of a different type of metal (mine was alloy) and the number and types of seals may be different. mine has square section seals inside the seal unit. fortunately these can be replaced by standard o rings.
    As parts varied / changed during the production of this range of rifles, please be aware you need your parts at hand to make sure you are ordering the correct spares.

    hope this helps

    I have been asked to include something about refilling the ram which I will below but firstly with a couple of caveats. The Theoben gas ram is a self contained unit that "should" need little if any maintenence, but the sealing inside the ram is via O rings and O rings do perish and fail. The schrader valves can fail too.
    If pressure loss / drop in power/velocity is detected the trick is to find why, not just to pump up the ram with more air. Any excess pressure added to the ram causes premature failure of the piston crown resulting in less power output.. add more air.. further destroy the piston crown etc etc. The sears can also give way under higher than normal pressure. Dont ask me how I know. It was 20 years ago and probably resulted in the first know gas ram to spring conversion ( landymick on here can vouch for this)

    as for filling there are 3 options
    1 the slim jim type pump. it works and may need 80 or so pumps give or take plus a few to charge the hose itself for an empty ram after rebuilding. the downside is you cannot measure the pressure in the ram and this pressure can be an indicator of how good your piston crown is. in any event check by chrono
    2 my personal preference - the stirrup pump. comparatively few strokes and for me, charge to about 600psi, then check with a chrono .because of the efficiency of a stirrup pump, when the rifle is in a near charged state, even half a stroke can have a dramatic effect on pressure. as said above once you know what your ram takes its a good indicator of the state of the piston crown. more pressure needed..... shafted or wearing piston crown.
    3 not a way I'd go but a bottle. for me not enough control over the amount of air going in and the volume inside the ram is tiny compared to a pcp bottle / tube.

    Please note. the adapter that fits the theoben ram is not the same as that for the HW90. An adapter can be purchased and some do have both the HW fitting and the Theo fitting and you unscrew one which exposes the other. A simple male/male 1/8 bsp adaptor can be had for a couple of quid that will connect the fill adapter to your pump whip/ fill hose.

    There are some good companies out there for anyone not competent or confident in taking this stripdown on. My vote would be Impact Airguns.
    Last edited by robs5230; 14-12-2015 at 10:08 PM.
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  5. #170
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    Hi ... excellent thread but could you add a guide to the pressure to pump the ram to, please? I realise you cannot be spot on, but it would help to get a guide pressure so that someone could then fine tune for a given output.
    A guide to equipt needed to pump up the ram may be useful as well.

    Cheers, Phil

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    stripdown

    Hi Phil.
    Charging info now included.
    Rob
    Last edited by robs5230; 14-12-2015 at 08:35 PM.
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    Thanks for this very detailed explanation Rob. It goes further than I expected but is all the better for it. I would be very surprised if any problems were caused by publishing a charge pressure ... I am sure it is available elsewhere on BBS threads ..... but I thought it would complete the picture of an excellent thread. I always find it interesting that the HW90 uses a lower pressure but have not really investigated why ... are cylinder sizes different?
    Overpressurising can be a real issue as I know from experience. Many years ago I bought a cosmetically perfect .177 HE at auction for a very good price. Full of anticipation when I got home, I chono'd it ... a measly 5ft lbs with a very hard cocking action. I had no experience of the Theoben gas ram so did not know the correct cocking effort but was surprised it was so hard. Similarly I had never serviced a ram so took it to Theoben. The diagnosis was over pressurising and a burnt out piston head. In this case I think it may have not been possible to pump it up over 12. My auction buy was still good value but it was a salutory experience.
    So ... thank you,
    Cheers, Phil

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    sizes

    Quote Originally Posted by Phil Russell View Post
    Thanks for this very detailed explanation Rob. It goes further than I expected but is all the better for it. I would be very surprised if any problems were caused by publishing a charge pressure ... I am sure it is available elsewhere on BBS threads ..... but I thought it would complete the picture of an excellent thread. I always find it interesting that the HW90 uses a lower pressure but have not really investigated why ... are cylinder sizes different?
    Overpressurising can be a real issue as I know from experience. Many years ago I bought a cosmetically perfect .177 HE at auction for a very good price. Full of anticipation when I got home, I chono'd it ... a measly 5ft lbs with a very hard cocking action. I had no experience of the Theoben gas ram so did not know the correct cocking effort but was surprised it was so hard. Similarly I had never serviced a ram so took it to Theoben. The diagnosis was over pressurising and a burnt out piston head. In this case I think it may have not been possible to pump it up over 12. My auction buy was still good value but it was a salutory experience.
    So ... thank you,
    Cheers, Phil
    I can only comment for the size of my piston crown which is approx 27mm dia. Other theobens may have had a 31mm dia one. The 90 i understand has a 30mm one.
    The 90 I have shot is a lot harsher than my fenman but as I stated above, a wide range of internal parts have been used over the years in theoben gas ram rifles which may have an effect on how they perform. Also drilled and undrilled inertia weights have been used. Mine is undrilled.
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    Well done Rob, some great info on here. Earlier this evening I rebuilt a .177 HE Evo and now that is back together the next job is overhaul of a .177 Sirocco with the lower pressure ram.
    Regards,
    Dave.

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    update

    Just to update on this rebuild, Thanks to the cracking lads at Impact Airguns this fenman is now back up and running and smooth as Silk. Impact have really pulled all the stops out to find me the bits I needed and I can't thanks them enough.
    Oh and this rifle with the 27mm piston is very smooth

    WORD TO THE WISE ..... If you do need Theoben gas ram parts they will surely be able to provide what you need, however you need to be very sure of sizes etc as there were definitely different parts used through the earlier years of production. So strip and measure the parts carefully before you order.
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  11. #176
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    Milbro G71 Strip (pt1)

    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
    Last edited by ggggr; 27-12-2015 at 10:10 AM.
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  12. #177
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    Milbro G71 strip (pt2)

    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.
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    Original 45 Revised

    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
    Last edited by Phil Russell; 13-03-2016 at 05:31 PM. Reason: typo

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    Fwb 124/127

    FWB 124/127
    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 ˝”. 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 ˝” 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.

    Cheers, Phil

  15. #180
    Join Date
    Feb 2010
    Location
    Swansea
    Posts
    6

    Some extra info on Merlin strip

    Quote Originally Posted by ggggr View Post
    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.

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