Idiots guide to classic airgun strips (pt 1)

[Phil Russell]

Part 1: The strip

ORIGINAL / DIANA MODEL 50 Strip and rebuild
Much also applies to the Model 35 break barrel

These notes are designed to help you strip and rebuild the Original Model 50 underlever rifle that has the feared ball bearing trigger. Much of the notes also apply to the Original Model 35 that has the same trigger assembly.

Strip:
Remove fore and rear sights.
Remove action from stock. There is a simple bolt in the trigger guard. The front of the stock is held to the action by a nut that fastens to the underlever catch. This is a round nut with cut outs in the rim. It is possible to carefully use a small screwdriver to turn this but I made a simple tool to fit over the underlever catch and turn the nut. The cross bolt through the action is also the underlever pivot bolt and holds the underlever in place. Action is now free, as are the underlever parts; underlever and cocking arm.
Remove the loading tap. Not absolutely necessary but makes life easier later as if left I found it interferes with my homemade spring compressor. Press down on the tap plate as you release the 2 screws as there is a spring laden ball underneath. Just release carefully and it will be OK. Do not lose the shims on the tap.
Remove the small barrel cover. This may be held by a small spring pin but I have seen rifles where the pin is missing.
Remove the action end cap.
FOR INFORMATION: Look at the end of the action. Note the inner circular sleeve about 15mm diameter inside the end of the action and the smaller (about 5mm) round object behind the sleeve and at the top of the action. The 15mm sleeve is the part that holds the 3 ball bearings (4.75mm ). It is about 5 cm long and locates against the spring guide. It is held in place by 2 cross pins through the action. Do not remove these yet! The 5mm round object is the end of a spring laden prod.

I now find it best to put action in a spring compressor, barrel to the left and trigger up.

The trigger needs to be removed. I find it best to drift out the trigger pin with a drift then, while holding the trigger in position, carefully remove the drift, so releasing the trigger and its spring.

You now need a socket or other implement that can be used to hold the 15mm sleeve firm while you drift out the 2 cross pins that retain the outer and inner sleeves in the action. The pin towards the barrel is smaller in diameter and acts as a guide, the other pin is larger.
Now carefully release pressure on the spring and let the sleeves be pushed out. As the inner sleeve comes out it will bring the smaller 5mm ‘prod’ out (that you saw above) complete with spring. Also coming out will be another sleeve (the outer sleeve) that fits inside the main cylinder. Try to keep these bits in their original orientation ... I place my left hand underneath them as they come out under the preload pressure, which is not great, about 5cm. Note that the 15mm sleeve is formed from rolled sheet and has the join uppermost i.e. in line with the trigger slot. The uppermost part of the outer sleeve is cut away towards the stock.
Remove these bits. The 3 ball bearings are found in holes in the 15mm sleeve at the left end.
The prod will fall free ... a prod and a spring about 4cm long.

The mainspring, spring guide and piston can now slide out.

Service as appropriate. The ball bearings are standard cycle size. I have seen triggers work with only 2 bearings in place but do not recommend this.

Part 2, the rebuild, in the next thread.

Cheers, Phil

[Phil Russell]

Part 2, the rebuild:

ORIGINAL MODEL 50 REBUILD.

Rebuild:
Nothing to fear really, but a bit fiddly at times.
Put action in the compressor, barrel left, trigger slot uppermost.
Replace piston, mainspring and spring guide. Make sure the piston is positioned with the underlever cocking arm slot uppermost.

Insert the large sleeve into the cylinder about 2cm, the cut out uppermost and pointing towards the stock end of the action.
Assemble the sleeve and 3 bearings ... a dab of grease in the bearing holes keeps them in place. Bearings fit in the holes from the outside. Insert this sleeve into the action, with the ‘join’ uppermost. Locate it against the piston sleeve. The spring and prod needs to be fitted but I found it easier to do this later.

With the socket against the 15mm sleeve, compress the sleeve into the action. This does not automatically move the outer sleeve in so I found it best to carefully move the outer sleeve in by hand (it is not under pressure).
Push the small sleeve in until to cross pin holes are aligned.
It is now time to fit the prod and spring.
I used a short length of cycle spoke to help ... put it through the left cross pin hole and release tension on the compressor. I expect the spoke will bend a bit at this point.
Now turn the action upside down so that the trigger slot points down.
Take the prod and spring and insert the spring over the top edge of the inner sleeve. You may need to lever the sleeve down a bit (hence the freedom to do this give by the spoke) to get it started. Feed spring and prod in as far as they will go. The raised lip of the prod now needs locating behind the rim of the inner sleeve. Push inner sleeve down while pushing the prod in. It will click into place.

Tension the main spring again using the socket. I now insert a drift, or if possible, the correct cross pin through the first hole before removing the spoke. If it is not possible to fit the first cross pin because of slight misalignment, use a suitable drift and then remove spoke and add another drift. It should now be possible to jiggle the alignment Ok by adjusting tension on the mainspring. Fit front cross pin, and then the second pin. You can release tension on the socket.
Turn action again so that the trigger slot is uppermost.
Fit the trigger by replacing its pin but without the spring.
The spring now needs to be fitted. A bit fiddly as it is quite strong.
With trigger fitted, use a blunt screwdriver to push the ‘outer sleeve’ down the side of the trigger so that the trigger engages. This gives a little more room to add the spring.
Locate spring on the nib on the action and compress spring so that it fits over the nib on the trigger blade. This is fiddly. I find it best to use a flat blade screwdriver, using the flat of the blade to push on the spring while I then nudge the spring into the trigger housing. Take care and all will be well.

That’s it .. hard part over.

All that remains is to replace the loading tap ... remember the little ball that sits on the spring in the tap. Replace the barrel cover bit and then locate the underlever into the action before feeding the stock over the lever. Refit the round nut over the underlever catch and refit the through bolt on the stock, making sure it passes through the underlever. Refit the rigger guard bolt. Refit sights.

Job done.
As I hope you will see, the ball bearing trigger is not too difficult. It is possible to fit it as a complete unit with the prod and spring assembled but it is more fiddly. If you want to do this, assemble the outer sleeve, inner sleeve and the spring and prod as a unit before insering into the cylinder. You then need to hold the prod and spring firmly in place as you wind the sleeve unit into the cylinder. It is possible with care.

When I first stripped a model 50, I had access to ‘Air Rifle and air piston maintenance and repair’ by Q Cobham ISBN-10 0-9553131-0-4 which gave me confidence to proceed. I supplemented my actions with more notes, upon which this account is based.

Cheers, Phil

[ggggr]

This is a slavia made break barrel pistol with a plastic body,a reasight adjustable for windage and a pivotting foresight adjustable for elevation. On the model I have, there is a knurled thing in the rear of the cylinder end cap, which unscrews and is actually a screwdriver for adjusting the trigger screw. remove this and keep it safe. The action is held in the body by a screw on either side of the body and a nut at the bottom of the pistol grip that may require a forked screwdriver to remove. Remove the two screws and nut and lift action from body( with luck the trigger spring should remain in the body) To remove barrel, undo lockscrew and barrel pivot screw. When you have done that you will need to knock out the front pin in the trigger housing otherwise you will not be able to remove barrel and cocking arm. With barrel out, you can remove pin holding barrel plunger in breech block and clean and lube and replace. There is no real need to remove trigger and sear although I think they would respond to a little polishing if you do. Before you attempt to unscrew cylinder end cap, remove the small pin on the underside of the cylinder that locates it (I used fingers but you may need a small screwdriver or long nose pliers) GO TO PART TWO

[ggggr]

You should now be able to unscew the end cap, using a large screwdriver at first and then your hand (remember to keep pressure on). When it unscrews, you can remove the guide, mainspring and piston. The piston head is a parachute washer which just seems to locate on a spiggot. The piston has slots on both sides but only one notch for the sear so make sure you put it back the right way round or the gun wont cock! The cocking arm slot would benefit from a bit of light,filing and polishing. Clean and lube. Replace piston (right way up), mainspring and guide and screw on endcap. I used a rigger glove to push down on the cap. Tighen the cap up but use a small screwdriver or pin to feel for the hole that the little pin locates in and then replace this when its lined up. Replace cocking arm in its slot and then replace the barrel and locate pivot screw and lock screw. Replace the pin at front of the trigger housing that keeps the cocking arm pushed down. Replace action in pistol body, making sure trigger spring does not come out and locates in the recess in sear. Replace two screws and the nut in the pistol grip.

[Garvin]

Paratrooper exploded view

Trigger detail

[Phil Russell]

Again maybe not quite a collectable but it is an old favourite and I note some forum members asking for advice at times. So here are some notes on the strip:

This guide gives instructions on how to strip the HW77 / 97 standard and Karbine versions. It does not contain information on tuning nor of stripping the Rekord trigger unit.

Tools required: 3mm punches (2), light hammer for punches, blade gunsmith screwdrivers to fit stock screws and trigger guard screws (no cross head screws), small adjustable spanner or spanner to fit the action retaining bolt..

Stripping:
Remove any telescopic sight and any rear sight.
Remove action from stock (2 x 5mm screws at the forend plus their retaining washers and 2 screws in the trigger guard). Remove trigger guard.
Lift action from stock.

Place action in a padded vice, barrel to the left and trigger uppermost.

Note the large threaded nut to the left of the trigger block. Undo and remove using the small adjustable spanner, taking care not to lose any spacing washers if they are loose. The anti-bear trap / safety slide is now free but held by the underlever.

Tap out the two pins that hold the trigger unit in place. I tap from front to back. The pins are of different lengths, a shorter top one near the end of the trigger block and a longer bottom one nearer the breech. Remove the trigger housing by tilting the trigger housing up and to the right. As you do this, keep a hand over the safety catch to prevent it pinging out. When the trigger unit is free, remove the safety slide plus its spring.

Remove the pin that holds the underlever in place on the breech and remove the underlever, raising it to disengage the end that goes into the compression cylinder slot. If you take care you need not knock the pin all the way out.
NOTE: if you are only replacing the spring and do not want to get at the compression cylinder and piston, you do not need to remove the underlever.

You now need to remove the end block that housed the trigger unit. The preload from the spring is not great but I advise wearing goggles and a glove on the hand you unscrew the block with.

Unscrew the block. It may be stiff to start, so you can place a lever in the trigger housing slot to start the movement. I use a piece of timber about 6” long. Take care as you unscrew the block, keeping watch on the screw threads. The block will suddenly lose the threads, so be prepared to support it with the gloved hand. Place the block on one side. The spring and spring guide can now be pulled out. If you removed the underlever, you can also now pull out the compression cylinder and piston assembly.

You can now service any parts you wish but at the least I recommend a clean of all parts and reassembly with fresh lubricant. I also fit a piston sleeve as a matter of course.
Next post: the rebuild
Cheers, Phil

[Phil Russell]

HW77 / 97 rebuild
Re-assembly:
This is basically a reversal of the above.
Begin by assembling the piston in the compression tube (remember suitable lubrication), making sure that the underlever slot in the piston lines up with the square hole in the compression tube. Fit this assembly into the action with the piston slot uppermost, in line with the underlever slot in the main action.

Refit the spring and spring guide, correctly lubricated, into the piston.

Now you need to refit the end block. With the block in your gloved hand, push against the end of the spring guide to bring the block up to the main cylinder. Turn the block to engage the threads. This is easiest done by pushing with the gloved hand and turning the block with the other. Screw the block into the action, taking care to look at the square hole in the cylinder and the slot in the piston to make sure they are not going out of alignment with the slot in the action. They can easily do so, but to stop or correct any movement I find it easy to hold a screwdriver in the slots to prevent the piston cylinder and piston tube from rotating. When you have screwed the end block in as far as you can by hand you may well need to apply some leverage to get it up tight. You can check this position by noting that the sides of the trigger housing slot line up with the action and the threaded bolt can be screwed into the block.

I now prefer to refit the underlever. Place the safety slide / antibear trap slide mechanism on top of the action and refit the underlever cocking arm end into the square hole and piston slot. Refit the underlever into the pivot at the end of the action and tap the pin home.

You can now secure the safety slide to the end of the action with the threaded bolt. Ensure the spacing washer is still in place. You need to push the safety slide a little against its spring pressure but it is easily done; refit the threaded bolt. Once fitted, just release the underlever and make sure the safety slide moves freely.

Now to refit the trigger. Refit the safety catch, remembering to put the spring on the catch before you push it through its locating hole in the end of the action. Hold the trigger unit with the left side slightly up and feed the trigger unit into the trigger housing, all the time keeping the safety catch pushed in against its spring. As you feed the trigger unit home, bottom right corner first, rotate the left edge down a little and it will fall easily into place. When the unit is seated, take two punches and place them through the holes in the action from the front to back, all the time holding the safety catch in. Then take the shorter pin and replace it through the action and trigger unit from the back towards the front. This will drive the punch out; the pin should go in quite easily. If it jams or refuses to go, do not force it; you will have the holes slightly out of alignment. Jiggle the punch to bring the holes into alignment.
Fit the long pin.

Make sure the captive nut at the top right of the trigger unit is in place ... a trigger guard screw fastens into this.

Refit action into the stock. Refit trigger guard. Job done. Refit sights and test rifle.
Cheers, Phil