Idiots guide to classic airgun strips (pt 1)

[Phil Russell]

Part 2: Now the fun starts.
The rebuild:
Valve assembly: Clean the valve body and replace components in order, making sure the seals etc lie flat and locate properly. To refit the circlip, assemble the circlip on the circlip pliers and compress it; holding the clip in the pliers push down on part 30I (check this is going to seal against the O ring, it goes with the wide seal side, narrow brass side, into the valve) to compress the spring and release the circlip when it is in position. Check it has located in the groove.
If you removed it, replace the black cap, transfer port and spring. Note the cap has 2 small lugs that need to be in the correct position on the lower side of the valve body in order to locate in the trigger housing. Refit the capsule components and tighten the locking nut.
Check the trigger safety link part 33: This is a bent rod in a sort of horseshoe shape with one arm longer than the other. One arm locates through holes in the flat bar that connects the trigger to the hammer. When the trigger is pulled, this rod moves up to cover the firing pin of the valve. The hammer then strikes the rod which pushes the valve pin in to release gas via the transfer port. Our rod was fitted with the longer arm located through the trigger bar holes, indeed the exploded diagram seems to show it this way. When I failed to get our pistol to fire after checking everything else, I reversed the position of this rod, placing the short arm through the holes in the trigger bar. The result was remarkable ... instant power. I wonder if the pistol had been assembled incorrectly from new.
When happy that all is well with the valve and safety link, make sure the trigger spring is located in its recess and replace the lh plate. You can now check trigger action. It should be smooth and if you look inside the hammer as you pull the trigger you should see the safety link rise to be struck by the hammer.

The time has now come to rebuild the pistol into the main body.

Trigger housing and shroud release catch: Take the trigger housing and place the shroud release lever on its locating peg on the lh side, the long arm to the left. Now look inside the main body and note that when you push down on the components at the muzzle end, they move up and down under spring pressure. Note there is a small lever on the rh side of these bits that comes up as the lh side bits go down. When reassembling the trigger block into the main body, you need to locate the shroud release arm under this small lever such that when the shroud release ‘thumb release’ is pushed down, the small lever moves up, pushing the shroud release mechanism down ... this releases the shroud and it springs forward under the action of the spring(s) over the barrel and guide rod. This can easily be checked when you think you have the trigger block in place .. just push the release lever down and see if the release mechanism moves down. While doing all of this, note that at the forward end of the centre of the trigger housing (just below the black cap) there is a groove (approx 1.5mm wide) facing inwards on each side. The shroud assembly will locate into this groove soon.... With the trigger housing assembled into the main body and the shroud release catch working, turn your attention to the slide and shroud assembly.

Shroud assembly: If the shroud assembly came free from the slide, you need to refit it. The barrel goes through the top hole and a guide rod goes through the lower hole. The barrel has a spring and retaining C clip. The spring needs to fit into a recess in the slide with the C clip next to a ‘guide plate’ in the inside of the slide such that the spring is pushing the barrel into the shroud. At the same time, the spring on the locating rod needs to be in place over the rod. It will be located properly later ... While this is going on, the barrel and locating rod both need to go through their respective holes in the end of the slide.
I found the critical part was getting the barrel spring and circlip to locate properly. I solved it by: With the barrel/shroud off the slide, slide the barrel spring over the barrel and add the C clip (if you have not removed the C clip, it will be in this state). Now take about 15cm of thin garden wire ... mine was green covered and maybe less than 1mm total diameter. Thread one end through the barrel spring. Compress the spring completely and use the wire to hold the spring compressed. Now, with the other spring over the guide rod, pass the barrel and the locating rod through the holes in the slide, making sure the C clip is on the inside of the locating plate in the slide housing with the end of the spring away from the C clip against the shroud body ( such that when you release the spring it will push the shroud back away from the muzzle). Remove the thin wire. You should now have a slide with the shroud assembly attached by the barrel spring and with a locating/guide rod with a spring spinning freely on it.
Look at the shroud assembly and note a guide bar on the lh side at about guide rod height. It is about12mm long. On the rh side is a much smaller guide, about 3mm long. These will locate in the grooves in the trigger housing.
During the many strips I did on my pistol I managed to damage the small guide (soft plastic!) but replaced it with a small steel peg (actually part of a steel rod from a needle roller bearing) superglued into the shroud assembly.

Now for some fun: you now need to mate the shroud assembly / slide unit into the main frame while: 1. Keeping the shroud release lever operational 2. Locating the guides on the shroud assembly into the grooves on the trigger housing and 3. (most difficult) locating the spring on the guide rod into its correct position in the main frame as the slide and main frame come together. This is how I (eventually) did it. There may be other ways but this worked for me even though it took many attempts to get it right:
Hold the main frame in left hand with trigger housing upwards. Hold it so that the trigger housing is slightly angled up at the rh end; it will not move much anyway but all movement helps. Keep the lh end in the mainframe or the shroud release lever can become detached.
Offer up the slide assembly. You need to keep this almost parallel to the main body and in the correct position such that the guides on the sides will slip into the grooves on the trigger housing. At the same time, the lh end of the spring on the guide rod needs to be caught against the rh face of the plastic plate that sits a couple of cm away from the rh end of the main frame. As you push the slide and shroud to the left, this spring compresses. If you get this wrong and the spring is not compressed against the plate in the body (by the plate being positioned somewhere along the spring) then the shroud release will not work. As you succeed in locating the spring and the guides / grooves, the slide will begin to engage again onto first the trigger housing and then the body at the muzzle end. The parts should snap together.
Check the action: Does the slide release and shroud work? Does the safety work? If not, then you must remove the slide / shroud assembly again and start again.

If all is well, replace the lh pin 15, replace the CO2 lever unit with the rh pin 15 and check pistol function.

If it all works, congratulate yourself on a job well done. While correcting our pistol I must have removed the top slide about 8 times while trying various methods to get it all back together. The method described here worked, many others, including assembling the trigger housing and shroud into the slide first (quite easy to do) failed because I could not then locate the shroud release lever into its correct position while fitting the slide unit back into the main body. Maybe perseverance would have seen me find a way.

Cheers, Phil

[ggggr]

Here we have the RO72. Undo the screw on the foresight and the two on the rearsight (you will have to remove elevation wheel to get at the rear one and dont lose the little post it pushes against) and remove sights and put somewhere safe. To remove the grips there are two screws on either side parallel to the cylinder and a larger and smaller one in the pistol grips (one locates in the other).Lift the action out and remove the endcap. You can remove the cocking arm pivot pins at either end of the cocking arm and remove the cocking arm.( the 2nd pin goes through a slot in the trigger housing and connects to a slider which has a ball bearing on it).Undo the nut on the RHS of the breech jaws with a forked screwdriver or similar and undo the barrel pivot and remove. If you want to change the breech seal do it now. If you want to grease the barrel plunger and spring, you will have to remove the small pin in the block that holds them. I would do it now and replace in the block. There are 2 pins near the middle of the trigger housing----if you knock these out you can remove the trigger. Slide out the cocking slider.The remaining pin at the rear of the housing holds the sear. Watch out for the hairpin spring that goes on the sear and locates on the out side of the housing, when you remove the sear. Go to pt2

[ggggr]

Use a bit of forked tube smaller than normal (see first few posts in thread) to compress mainspring and remove cylinder pin. Ease pressure and remove guide,mainspring and piston. The piston washer on this was rubber (see end of this post). Clean and lude and replace piston,mainspring and guide. Compress mainspring and refit cylinder pin. Replace barrel and locate the pivot pin and lockscrew and tighten. Replace the cocking slider in the trigger housing and then replace the cocking arm and the 2 pins (one at the breech block and the one that goes through the slot in the trigger housing and joins it to slider). Locate the trigger and replace its 2 pins. Locate the sear and make sure it,s spring is located on it, with the other end hooked on the outside of the trigger housing. Fit the endcap with flange pointing into grips and repalce the grips and the 4 small screws and the larger and smaller one in the pistol grip. Replace sights. This is not a bad plinking pistol although crappily made. You could replace the piston washer with leather or get someone to turn a bit of ptfe or alloy and fit an O ring. The trigger is adjustable via the large screw visable through the underside of the grips but does not do much. It is possible to move it too much so the gun will not cock. At least you can strip this pistol because it has pins instead of Rivetts but I would guess spares are hard to get. Not a bad "Tin can gun" though.

[Gareth W-B]

Sterling work Guy, sterling.

[MattyBoy]

Here is a guide to accessing the 2 parts of the Sharp Innova which usually give problems; the exhaust valve and the air cylinder.

So to access these you leave the muzzle end of the gun well alone.

Open the pump arm - this removes any positive or negative pressure on the guts of the gun - the bit we want to get to.

Take off the stock by undoing the single large phillips screw in the trigger guard.

Put the stock to one side.

Remove the brass threaded collar into which the stock screw went.

Take out the threaded long grub screw which goes through the breech block into the compression tube/ air cylinder using a normal screwdriver

Carefully jiggle out the compression tube from the breach block catching the shim as you do it. Do not lose the breach seal O-ring in the process!

Unscrew the cover at the bottom of the compresison tube with a pair of thin nosed pliers and the exhaust valve assembly will fall out.

Keep the bits in the correct order!!!

Once the exhaust valve assembly is out you can close the pump arm which will create positive pressure and force the air cylinder out of the compression tube.

You can now degrease the valve assembly and if required unscrew the air cylinder to degrease that too. Don't lose the spring and ball bearing.

It's advisable to replace all O-rings when you do a back-end strip of an Innova. Most parts are available from Chambers.

Contd...

[MattyBoy]

Putting the back end back together is a reversal of the above procedure but I'll add a couple of hints:

Having opened the pump arm again, push the air cylinder carefully back up the compression tube after putting a smear of silicone grease on the large O-ring. Line up the hole for the long grub screw in the air cylinder with the hole in the compression tube, this can be tricky, (it's the smaller of the 2 holes in the compression tube), and screw in the grub screw. This will now enable you to replace the exhaust valve assembly without pushing the air cylinder up the compression tube.

Screw the exhaust cover back in "less than finger tight" if you know what I mean. This is to ensure that the long grub screw threads are not binding with the hole in the compression tube - otherwise you'll have a nightmare getting it out and back in later

Once you have the rear parts back in and the air cylinder is correctly positioned so that the long grub screw is freely removable, remove the long grub screw

Now you can replace the compression tube back into the breech block.

Make sure the breech seal O ring is correctly seated in the larger of the 2 holes in the compression tube, helped with a smear of silicone grease, and that it is not displaced as you slide the compression tube back into the breech block.

Once the compression tube is fully home and you have screwed the long grub screw in 2 turns, the shim can be slid carefully into place.

Once the shim is in you can fully tighten the long grub screw and then replace the brass threaded sleeve and re-attach the stock.

Simples

Matty

[Phil Russell]

gggr (Guy) has already posted about the RO72. Today I had reason to strip a RO71 ... basically the same pistol ... but did not need to completely dismantle it to correct the fact that although it would cock it would not fire. Here are a few notes:

Supplement for RO71: if all you want to do is service the piston, it is possible to do so without disturbing the main components of the trigger:
Remove grips as above. Undo and remove the barrel pivot pin as above but keep barrel and cocking arm roughly in position. Place pistol on a flat sheet, barrel to the left. Remove the 3 screws that secure the lh side plate of the pistol. Carefully lift the plate away ... the trigger assembly will stay assembled on the rh plate.
Lift the rear sight brass studs away from the top of the action. Lift barrel and cocking arm away to the left. Piston assembly will now lift out.
Take assembly apart as above ... there is little preload but take care.
On our pistol the trigger would cock but the piston was sticking and pistol would not fire. Examination of the piston assembly soon showed why: I guess someone had had the pistol apart before and had caught the leading edge of the plastic piston seal on the cocking slot during assembly. This had shaved a fine sliver of seal away from the leading edge of the seal which was jamming the piston. The unit was also lacking any lubrication. I cleaned up the piston seal and applied a smear of SM50 to the seal, a smear of moly grease to the spring and piston outer surface and re-assembled. All works perfectly now.

Cheers, Phil

[ggggr]

I did one of these the other day. The strip down is the same as the Diana 22/23 near enough. On the one I did, there was an extra bobbin between the guide and the sleeve that holds the mainspring in and the piston rod seems odd (problem mentioned in my post of 4/11/2010). You cannot be sure with some of the later Milbro stuff. They did seem to go very British Lelandy in the 70,s and I would say that unless you are a collector, you are better off with an earlier 22/23 or Webley Jaguar/Junior/Ranger. Sorry this is not detailed but its easier for me if you look up the 22 strip than me typing out a full strip down.

[Phil Russell]

I really thought these models had been covered, but apparently not. Here are some notes I made a while ago:

IMPROVED MODEL D, STANDARD, LADIES MODEL ETC

The following can be regarded as a generic instruction even though differences will be noticed in certain parts of the trigger block, loading tap, stock design and sighting system. For a good account of the rifles see: Hillers Guide to Air Rifles, edition three or four.

On all these models, the half stock is held to the trigger block by a bolt through the stock. The stock is removed from the action by removing the buttplate or wooden plug (take care it does not split in two) and unscrewing the stockbolt that goes through the stock into the triggerblock. Stripping the rifle is easiest if the stock is removed: remove trigger guard; two front screw bolts (possibly 2BA) and a rear screw or maybe just the front bolts with the rear being inset into the trigger block. Remove stock bolt and pull stock away from the trigger block. Note locating pin from the block.

If this bolt is seized and its absolutely 100% necessary to remove it, remove the action from the trigger block, take out the trigger mechanism, soak the back of the stockbolt in the triggerblock with a little penetrating oil (don't soak the stock wood), leave it a few days, then put a piece of suitably sized flat steel bar into the trigger recess, place it on a flat non damaging surface and then try to turn the stock bolt using a large screwdriver or socket set - I do this at the bottom of the stairs and kneel on the block, with the wood over the edge - though you could probably put the steel bar into a bench vice and do it that way.
Proceed very gently though as the stocks can be delicate 100 years on. If you do it by this method properly, there should be no pressure on the stock wood.
It may help just to give it a 1/8turn in the tightening direction - sometimes works to help it break free.
If the stockbolt is mashed - according to the experts you can use a Lee Enfield one off the bayofee which are sometimes cheaper than the parts suppliers.

The securing bolt may be a long one or a short one with a screwdriver slot or a hexagonal bolt head. The hexagonal bolt head version, especially if the bolt is a short one set deep into the stock, will need accessing by use of a box spanner or two or you may be lucky and find enough clearance for a socket. Normally a 17mm head size fits.

Trigger block unscrews from the cylinder but you may find it easier to remove trigger and trigger spring first. But this does not have to be done in all cases ... just examine the layout and judge whether or not the block will unscrew free of interference from the trigger as the block unscrews. Very often, keeping the trigger in the ‘pulled’ position will allow the block to rotate freely until the end of the cylinder clears the trigger. There can be some preload so be prepared. I prefer to mount the cylinder in a padded vice as the block is unscrewed; wearing a padded glove. When the block is free, it is possible to withdraw the spring.

It is possible to remove the stock and trigger block as a unit. To do this, just remove the two trigger guard screws that secure the guard to the action. Pull the trigger and unscrew trigger block and stock from the action.

To remove the piston, release the underlever pivot bolt and slide the lever and cocking link free. The piston can now be removed for inspection. The piston washer is secured by what appears to be a 2BA screw. These often break and if yours has, it will be necessary to remove the stub and either replace the screw with a new one or retap the hole. BSA are known to have used odd thread sizes (also used on early bicycles) so it may not be exactly 2BA .. but it fits. A new leather piston washer is easily made. Clean the inside of the cylinder.
If the spring is worn or broken, an AirSporter spring will fit. Early models had twin springs, wound in opposite directions. From experience there can be quite a lot of pre-load to them which can make refitting the trigger block a bit of a job.

Tap designs vary and if you wish to remove it proceed carefully when removing screws etc as there may be a spring or ball or both beneath any housing. Just be careful and it should be obvious how the parts go back together.

Re-assembly is a reversal of the above. When refitting the action to the trigger block I find it best to secure the trigger block in a rubber padded vice and offer up the cylinder/action to the block. It can help to have a small piece of wood, maybe 2” x 2” x 1” thick with a recess drilled in the centre and to place the barrel in this recess. Then you can push against the barrel to locate the cylinder on the trigger block thread while turning the action with your other hand. Once secure, refit trigger parts if necessary, refit underlever parts and refit the stock.

There a few differences in models, usually associated with the tap arrangements and underlever catch, but these do not really affect a routine strip and rebuild.

Cheers, Phil
With contributions from silva and gggr

[ggggr]

It,s up to you if you want to remove the sights. Remove 2 front stock screws and the rear one which is at the back of the trigger guard.Take action out of stock and remove the cocking lever pivot, (1 screw and a lock screw on the other side) and remove cocking lever and cocking arm. It looks like there should be shims in there but mine did not have any. If you look down the block the lever came out of you will see two cap head screws. Undo these and you can remove the block along with the barrel and the tube that holds the loading bolt. Watch out for the small O ring that sits on top of the cylinder (think crosman). If you want to get to the loading bolt, unscrew the endcap on its cylinder and then undo the small grub screw that you should be able to see once the cap is off. You can now undo the little bolt that screws into the main loading bolt and remove it. The bolt and it,s spring should now come out.(look out for where the small transfer hole is so you get it back in the right place) You will see a small O ring on the bolt and you can change this if you want. Clean and lube the bits and replace them, spring, bolt, small bolt, grubscrew and endcap. You can put this to one side while you strip the trigger and cylinder. Go to pt 2