Idiots guide to classic airgun strips (pt 1)

[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

[ggggr]

If you remove the rear trigger pin then the trigger and it,s spring should come out. Watch out for the small sear spring that goes into a welded in block at the bottom of the trigger housing when you go to remove the sear. Take note of the sear position and remove it,s pivot pin and remove the sear and the small spring mentioned above. Put a bar through the hole in the cylinder end cap and (keeping tension on) unscrew it. Once the block is undone the mainspring and piston should come out. I actually used an allen key to loosen the piston washer bolt while it was still in the cylinder to try to minimise the risk of damaging it on the threads at the end of the cylinder. The bolt holds on the piston washer (ptfe on mine) and an alloy spacer. Clean up and lube the bits and reassemble the piston,washer and spacer and put them in the cylinder(I again left this loose until the washer had cleared the cylinder threads). Replace the mainspring and screw up the endcap. Replace sear spring into its housing,then the sear and pivot pin. Replace trigger spring and trigger and locate its pin. Locate the small O ring on top of the cylinder and replace the barrel, loading lever housing etc, watching you dont dislodge the O ring. Replace and tighten the two allen screws that hold the block to the cylinder. Replace Cocking lever and arm and the pivot screws. Replace action in stock and tighten up the stock screws, making sure the rear one lines up with the thread in the loading bolt cylinder. (think crosman again).

[Phil Russell]

I forgot I had written these notes: they may help. All is pretty straightforward except getting the trigger / safety back together which is a bit of a fiddle until you get the knack. All is explained here:

CROSMAN 766 STRIP

Taking apart.
Remove barrel band (2 halves, single small screw goes though band)

Remove barrel band ends: plastic, lifts away.

Knock out the pin holding the pump lever to the pump tube.

Remove pump lever with pump attached.

Remove barrel: hex key on top of action.

With the breech block on its side, screws uppermost, stock to the right, remove the 4 screws. Keep top plate in position while doing this.

Gently prise the top plate off the bottom plate. Take care the pump handle plastic grip holder, black plastic sprung laden bit on left, does not ping out as you release the top plate. Top plate may come away with the trigger and safety catch or may leave trigger and safety in the bottom plate. Either way the trigger safety spring may become detached from its location on the safety. Do not worry. Remove trigger, spring and trigger pin.

Note position of trigger sear components.

Lift sear away, taking care not to lose the large spring that acts on the sear bar. Lift off the long spring and plastic peg that acts as the BB follower from its channel.

The valve housing is held by a screw to the left of the valve housing. Before releasing this, note the brass component at the top of the valve body towards the left. This has a small spring over it. Release and remove the screw holding the valve housing but hold the housing in position. Now gently lift the housing away to the right, catching the small spring on the brass piece and also noting that the striker piece and a black plastic end body will be released under spring pressure on the right hand side. Just go slowly and this component will not be forcibly ejected. The brass valve body will slide out of the air cylinder. If it is an easy, loose slide then inspect the O ring as it will most likely be worn.

If needed, replace O ring.

Clean all parts, especially the air cylinder.

I have not dismantled the valve.

Rebuilding
Reversal of above but these tricks may help.

Assemble valve body and housing into place in the air cylinder. Have the brass component in place but do not fit spring yet. Take care that the striker and its spring and the black plastic end cap are located correctly. Replace the screw to hold the valve housing.

Carefully replace the small spring over the brass component. There is just enough room to wiggle this over the component; it stays in place against the bottom plate.

Refit trigger sears in place and slip the sear spring into place.

Refit the pump handle retaining spring and catch ... take care it has a habit of falling out.

Refit the trigger and its rod with the safety spring under the trigger and the hooked end pointing up. At this stage I found it best to hook a small bit of thin wire over the long arm of the spring and feed it towards the trigger such that when the top plate is replaced it protrudes out of the trigger guard.

Replace top plate: a bit fiddly to do this and keep pump handle spring in place but persevere.

When located, pull on the bit of wire to pull the safety spring long leg downwards ... look through the hole for the safety catch to see if it has cleared the hole. When it has, feed the safety catch back into place and release the spring. Pull the bit of wire out.

Replace 4 plate screws.

Refit barrel, and pump etc.

Job done.

Cheers, Phil

[ggggr]

I got this the other day and thought I would do a strip down. Remove rearsight if you want. Remove the front and rear stock screws ,the trigger guard screw and the trigger guard and lift the action from the stock. To be able to remove the barrel and cocking arm, you will have to drift out the small pin in the housing the cocking arm passes through. Undo the barrel pivot lock nut and undo the pivot bolt and remove the barrel. If the breech seal needs changing then do it now. Remove the endcap from the cylinder. Unhook the trigger spring off the tang on the cylinder/trigger sleeve. Knock out the trigger pivot pin (front one of the two pins) and remove the trigger. Using the bit of forked tube tool ( mentioned early on in the guides) or similar keep pressure on the sleeve and knock out the 2nd pin. (I managed to hold the pressure with just my bare hands but use the tool just in case). Release pressure and the tube should come out,followed by a washer and the spring guide. Remove the spring and the piston. Clean everything up and lube. The example I got had no piston seal. It think it should be a synthetic seal held on by a metric screw (3mm I think). I made up a leather one to replace it. Replace the piston,mainspring,guide,washer and sleeve and compress with the tool to enable you to get the rear pin through the cylinder. Go to pt 2

[ggggr]

Enter the trigger into the housing and line up the holes with a punch and replace the trigger pivot pin. Refit the trigger spring onto the pip at the rear of the trigger and the tang on the housing. Replace cylinder end cap. Slide cocking arm through its housing an locate it. I would screw the barel pivot home now to hold everything in place while you refit the pin in the cocking arm housing. Replace the barrel pivot bolt lock nut. Replace action in stock and refit the stock bolts and trigger guard. Replace your rear sight.
I was surprised that this gun is the same size as the Diana/Milbro 22/23/76 and Webley junior/jaguar/ranger. Apart from the sights being better than the other guns mentioned, I did not think it was much better made. The weak point on the other (non tinplate) guns is the piston can wear at the point the cocking arm pushes on. The Hw25 piston did not seem much better made. Obviously the hw has decent scope grooves but unless you are intent on paying £140 + for a new gun, I dont think the hw justifies the extra money as a starter gun over the other guns mentioned. It seems to plink ok but then so do the others. It,s a pity some of our engineers on here have not made up a better piston to fit the Diana/webley range of small rifles.

[ggggr]

If you want to take off the sights then the rear is held by the elevation wheel and a screw at the front of the spring steel plate. The front sight (early model I guess) is alloy. You will need to undo and remove the small screw on the side that nips it up and then tap it off the barrel. Remove the two front stock screw and the 2 rear ones on the trigger guard and lift the action out of the stock and remove the plastic end cap. The cocking arm can be lifted out of the slot in the cylinder but remain connected to the breech block. Undo the barrel pivot screw and remove the barrel. Watch out for the plastic washers on either side of the breech block. If you want to clean and lube the plunger and spring, do it now. You need to knock the small tube that passes through the breech block with a punch. As you withdraw the punch the plunger and spring should fly out. Clean and lube and replace them and refit the tube and the 2 plastic washers. You will need a 10mm spanner to undo the stock nut/trigger nut from the captive bolt that passes through from the inside of the cylinder. Look how the trigger spring goes (one leg behind the trigger and the other pushing against the inside of the cylinder. Undo the nut and remove the trigger set up and the captive bolt. Go to pt2

[ggggr]

Use your special tool bit of forked tube (read first few posts in the guide) and compress the mainspring and remove the cylinder pin and then ease the tension and remove the gude,mainspring and piston. The piston set up on the one done was a leather washer with a plastic buffer in the centre and also a spacer underneath. It was held on by a small screw. If the leather washer is damaged, you can make one up. if the rest is damaged then I would buy new. Clean and lube everything up and refit the washer set up to the piston. Fit the piston, followed by the mainspring and guide. Compress the spring and refit the cylinder pin. Put the captive bolt through from the inside of the piston and refit the trigger housing (making sure the trigger spring is in the right position, with one leg behind the trigger and the other in the cylinder) and nip up the stock nut/trigger nut. Refit the plastic end cap. Refit the breech block and the barrel pivot bolt.Locate the cocking arm in its slot in the cylinder. Put the action in the stock and refit the trigger guard and stock bolts. Refit the sights and dont forget to nip up the small screw on the side of the foresight.

[ggggr]

I would not attempt this until you have done a few guns. It is fairly simple in design but the trigger pins are a swine to get out and there are a few other things. I will say that if you make up a couple of long slave pins for for fitting the cylinder end pin and sear pin + a short one to hold the barrel plunger while you attempt to refit that, you will make things easier for yourself. A dremel might help to ease the trigger pins rather than trying to move them a bit and file them ( like I did). If you have taken notice of this we will begin.
You can remove the rearsight adjuster screw if you want and the little sprung pin and spring that locate it. Remove the 2 side stock screws, the long one through the pistol grip and the trigger guard screw. The trigger guard should lift off and the action should come out of the frame. The long middle sear does not need to come out but everything else does. The sear spring has a small piece that sits on it at one end and a tang on the cylinder at the other. You could try to compress it and get it off but I would do it like this. Knock out the front of the 2 pins in the cylinder (holds the sear) and as you withdraw the punch, keep pressure on the sear until the punch is out. Slowly release the pressure on the sear and it should come away from the spring and the small piece (be VERY careful as this could fly for miles, which is why I suggest doing it this way). When the sear is out you will see a small pin coming out of the end cap into the cylinder. Remove this with tweezers. It is the pin the trigger adjuster screw pushes against. Now knock out the rear of the 2 cylinder pins and keep pressure on the end cap as you remove the punch. The endcap,sleeve and mainspring guide and mainspring should now come out. Now remove the trigger pivot pin. Notice how the short leg of its spring sits in it and the long leg pushes against cocking arm retaining pin above it. Remove trigger and spring. Knock out the cocking arm retaining pin. Break the barrel and knock out its pivot pin. Watch out for the barrel plunger pin and spring flying. You should now be able to lift the cocking arm out of the cylinder and remove the barrel. There is a plunger and spring on the cylinder as well, held by a grub screw underneath. Undo the screw and remove the plunger and spring and clean,lube and replace now. The piston should come out of the cylinder . It has a leather washer with a fibre buffer, held by a small screw. Clean off and lube all the bits and get ready to put back together. Replace the piston in the cylinder and then locate the cocking arm. Replace the cocking arm retaining pin and then locate the barrel with it plunger and spring in the breech jaws. A short slave pin really would help! Replace barrel pivot pin. Go to Pt2