Idiots guide to classic airgun strips (pt 1)

[Phil Russell]

THE MIDLAND GUN COMPANY DEMON DELUXE (AND DEMON)

This rifle, serial No. 878, is a .22 Demon Deluxe and would date from the mid 1920s, I think. Overall it is in good condition although close inspection shows that it has had some refurbishment as there are signs of minor pitting to the action and the stock seems to have been re-varnished at some point. The engraving on the action; a feature that distinguishes the Deluxe from the standard Demon is in good condition and extends to all screws. The top of the barrel flat is stamped ‘The Midland Gun Co, Birmingham Made in England. A test fire showed a very smooth action but output was thought to be on the low side. The rifle dieseled badly with every shot including some smoke from the breech area. It was time to investigate further.
If you have ever stripped similar rifles e.g. pre-war Diana 27 then the format of the rifle will present no problems but there are a couple of things to note. I began by removing the barrel and cocking slide as a unit by removing the barrel pivot keeper screw and then the barrel pivot screw. The breech block was a bit loose in the cylinder jaws. It was possible to tighten this up by tightening the pivot screw but the keeper screw would not then fit. A shim washer under the pivot screw solved this … there was one washer there already. It would have been OK if I had just removed this single shim washer but I thought it best to keep a shim there.
The butt plate was next, two screws. Look for the stock retaining nut visible in the hole in the end of the stock. Just loosen it; mine took an 18mm af box spanner. Then back off the trigger adjusting screw a couple of turns and remove the two front trigger guard screws. Note that the rear guard screw passes through the action to screw into a small angular steel plate on top of the stock. Remove the screw and the guard. Now undo the stock retaining nut and remove the stock. I expected to find that the steel rod holding the stock had a hole drilled through it where it screws into the trigger block but mine only had a ‘half a hole’ as if the rod had snapped in half at this point sometime. I could have drilled another hole further back but left it ‘as is’.
Now remove the trigger. Remove pivot screw and remove the screw while holding the trigger blade. When the blade is free from the action, pivot it on the trigger spring and lift clear.
Turn attention to the cylinder. Clamp trigger block in a padded vice and unscrew cylinder. Preload is not excessive at about 35mm but present so take care. When unscrewed, remove spring and piston. It was clear why the action was so smooth … the inside was liberally coated in enough grease to service a London bus. And it looked like standard wheel bearing grease. The piston washer was, as expected, leather and was in excellent condition. There was some light scuffing on the piston rear which was removed. Everything was cleaned of the old grease. The spring looked OK, nice and straight and fitted the piston and guide well so it was not changed. It measured 34 coils, 239mm long, 3.03mm wire, 12.8mmid, 19mmod. I later found a picture of the parts on the Vintage Airgun Forum and the spring shown was a bit different at 38 coils. The Demon here had come to me with a spring marked 'Demon': 38 coils,2.73 wire, 18.6od.
The leaky breech seal was replaced with a new made leather one .. ½” od with a 5/16” inner hole x approx. 2mm thick.
Note that if you only want to access the spring and piston there is no need for a full strip. Simply remove the two front screws from the trigger guard and unscrew the trigger block, trigger and stock as a unit from the cylinder. To access the piston you will need to remove the barrel and cocking link or just the cocking link as well.
Reassembly is the reverse of the above. I used moly CV grease on the spring and piston. A light lubrication of the leather washer followed. I added a slip washer to the base of the piston and clamped the cylinder in a padded vice and offered up the trigger block in order to get them back together. I tried the reverse but found it difficult as the piston rod is a good fit in the spring guide and getting it aligned perfectly against the preload spring pressure was difficult. Somehow, clamping the cylinder made it easier. When doing this make sure the cocking slot in the piston lines up with the slot in the cylinder.
With the trigger block in place, replace trigger. Hold trigger and its spring together and add the end of the spring into the recess in the block. Swivel the trigger and feed it down against spring pressure until you can add a drift through the pivot hole to hold it all in place. Now feed the pivot screw through to replace the drift and secure the trigger. Make sure the trigger moves back and forth against spring pressure. Return the adjuster screw to its original position.
Add barrel and cocking link, ensuring any shims are present on the pivot screw and that it is possible to add the locking screw to lock the pivot.
Make sure that the stock securing rod is positioned correctly to allow the rear trigger guard screw to pass through it. Add the stock and its securing nut but do not tighten fully. Add trigger guard and the rear screw, making sure it passes through to locate in the angular plate on top of the stock. Just nip tight. Add the front guard screws. Tighten the stock securing nut then tighten the rear guard screw.
While doing this service I noted that all parts were stamped with the serial number 878, including the inside of the butt plate.
Add butt plate. Job done.
On testing I found that AAF were a loose fit and seated maybe 3mm into the breech. 5.6mm Marksman and 5.6mm Wasps (new version) seated higher. There was still some dieseling which I have put down to the leather piston washer being impregnated with oil etc. The action was a little noisier which I put down to the amount of grease I scooped out.
Performance came in at around 6 - 6.5 ft lbs excluding higher readings from obvious diesels.
However, the extra noise bothered me so I stripped the rifle again and replaced the mainspring with the 'spare' that had come with the rifle. There was maybe an extra 25mm preload which made fitting the spring more of an effort as the piston rod was a good fit in the spring guide and both had to be perfectly lined up against the preload pressure. But on completion, a test showed the previous noise had gone. Performance was the same but the rifle was much nicer to shoot. I shall leave it alone now.
Maybe these figures are still influenced by dieseling but I am happy. And now quite fond of the old girl.
Cheers, Phil

[ggggr]

I've copied this from what I put up elsewhere in reply to a Senior not cocking, but the basic idea works with all the Webley over lever pistols.

"Ok. Here is what to do.
You have removed the mainspring? Put the guide back in and leave the barrel and linkage off the gun. Slide the piston back with a screwdriver or similar. Hopeully the piston should engage.
If it doesnt, then remove the guide and slide the piston a bit further back and see if it engages. If it now engages, check to see if you have the right piston in it. A Senior one should have a bronze ring as a seal. Mk 1's have a leather seal and Premiers and later guns usually have a Ptfe seal. All the pistons will go in but they will not work.
IF a new sear has been fitted at some point they sometimes need bit of the holding face grinding away to allow the piston to engage.

Assuming that the piston engages while you have the guide in, then try to push it forward a bit against the sear and the sear should hold.

If the sear does not hold the piston then either your sear is worn or the holding ring face on the piston-- Or both.

If with the guide in the piston does engage then that would suggest worn linkages/ cocking shoe, or the fulcrum on the cylinder being worn.

Usually bent pins are not the cause of a gun not cocking, but rather a symptom of people using excessive force to try to get the gun to cock.

More often that not, the problems start with a worn cocking shoe."

[ggggr]

This is a very basic strip of a pre war Diana model 19. There are some versions with safety catches and some badged as Ansonia.
The came to me for checking out and repair and was hammered with Car type Moly grease.
When it came here, the barrel and cocking arm were already off ( for easy packaging), but it is just one bolt to undo on the barrel pivot and the cocking arm has a rivet through it. The cocking arm slides in a housing on the cylinder.
I didnt even remove the barrel catch on this , which is a thumb catch on the LHS, as the pin was peened over and the catch looked good.

On this version, there is a bolt through the trigger housing and trigger guard. Once you undo that and the trigger guard to stock screw , you can either unscrew the trigger housing, pulling the trigger, or remove the trigger first. The trigger pivots on a pin through the housing and has a spring on a pip at the back , and sits in the stock. Im not sure if it should locate on a pin in the stock or have a guide pin, but it functions as it is.

As you unscrew the trigger block , keeping tension on it, it should come out and you should be able to get to the mainspring and piston. The guide is a part or the block.
I didnt try undoing the stock bolt on this gun as the stock had split and been repaired at some time.

The mainspring on this one is probably original as it was a fairly thin flat section one.
The piston washer on this was just a flap of leather, so I had to make a cup washer for it.
The piston washer is held on by a small screw (4mm).

Clean and lube your bits and go to part 2


Ps --link to pics on Dannys site. https://forum.vintageairgunsgallery....ble-prototype/

[ggggr]

Put your piston and mainspring back in and screw on the trigger block.
Replace the trigger in the block. Locate the trigger spring on the trigger and into the stock and then replace the trigger guard, then screw into the stock and the bolt through the front of the trigger housing and trigger guard.
Locate the cocking arm in its slot and line up the breach block in the breach jaws and replace the pivot bolt.

I found this gun a little uncomfortable to shoot with it being so small. Also on this one, the foresight post has been broken and needs building up by welding or soldering, so the gun shoots high.
I was surprisingly accurate even though the trigger was a little heavy due to the spring I fitted to the trigger.
It was a bit punchier than I was expecting with the mainspring being thin and a bit kinked. I wouldnt try a harsher mainspring as there is very little "meat" in front of the holding face of the trigger.

I think something like this would be ideal for teaching a youngster to shoot, due to its size, weight, build quality , basic sights and lack of a safety. It also has the "FUN FACTOR" that something more modern might lack for plinking.


https://forum.vintageairgunsgallery....ble-prototype/
For a bit of garden fun, learning to shoot and plinking, Id say its pretty good.


Just a small update. I took the butt plate off today and there is 24 stamped on the stock and it appears to be a 7 above it.

[Phil Russell]

DIANA 26 underlever

!933-1940. Note that this model, sometimes referred to as the 26U is not related to other model 26, break barrel rifles.
This model, .177, stamped 2 38 on the serrated butt (February 1938) is in overall very good condition although most screw heads show signs of removal due to some screw head slots being a bit mangled. Cocking was very smooth and quite easy. A chrono test with JSB Exact 8.4, Superdome 8.3 and Marksman all gave performance hovering on 400fps for around 3 ft lb. I believe this is about on spec for this ‘youth’ rifle and is on a par with other junior rifles. A tap test using damp tissue showed the tap to be good.
I did wonder if performance could be improved a little though so embarked on a strip to see what the mechanics were like. If you plan a strip of this rifle I recommend a spring compressor … see later.
Stock removal is 2 screws on the forend and the front trigger guard screw. There is no need to remove the trigger guard rear screw as it only fastens the guard to the stock.
Unscrew the end cap and look at the trigger. Note the trigger pivot pin also holds the trigger cage into the cylinder and with it, the mainspring. The mainspring etc cannot be removed until this pin is pushed out and the trigger removed. With action in a compressor, use a suitable drift to take up spring pressure on the cage to relieve pressure on the cross pin. I used a suitable ½” square drive socket. Push out the pin. The trigger is now free to remove complete with the trigger return spring. With trigger removed, release tension on the trigger cage and let the mainspring push the cage out of the cylinder. There was very little preload on this rifle. With spring tension gone, remove the cage, mainspring and spring guide.
Spring spec: 30 coils, 2.65mm wire, 18.45 od. Spring guide was a good fit.
Tap inspection: The tap is held in position by 3 screws on the lever side. The central screw needs to be removed before the 2 outer screws as it acts as a lock screw. As you remove the side screws, keep pressure on the cover plate as it is lightly sprung loaded. Remove carefully as there is a small ball bearing under it which sits on top of a small spring in a hole in the tap body. The tap can be removed for cleaning but note there may be shim(s) under it. My tap had a single, home made looking, shim fitted. With all cleaned, I applied moly grease to the tap and surfaces before reassembling. I tested tap alignment by firing a pellet into a rag and examined the head and skirt. I could see no deformation meaning that the tap alignment was OK.
To remove the piston, the cocking lever needs removing: remove the pivot pin lock screw and then the pivot pin. It helps to have the lever released from its locked position. Remove cocking lever. Piston can be removed. The leather piston head looked fair but inspection showed it was rotten with the sides separated from the central disc. It is held in place by a screw; this was tight so application of releasing fluid and light taps on the end were needed. Remove screw and the dished steel washer followed by a leather spacer washer, the remnants of the piston seal and a further backing washer. The piston seal is 25mm diameter. I made a new seal from 3mm thick leather.
Rebuild: All sharp edges on the piston body were removed and the piston cleaned. With the new, supple leather piston seal in place on the piston I compressed the seal slightly using a jubilee clip such that it would enter the cylinder easily. A smear of moly grease was put on the piston and it was pushed into the cylinder; pre-compressing the seal made this easy but do not waste time as the seal can quickly expand a bit to make fitting more difficult.
To see if performance could be improved I decided to fit a new mainspring. I did not have an exact replacement of 2.65mm wire x 30 coils so decided to try an alternative of 3mm wire for which the id was a good fit on the spring guide and the od was fine for the piston. I calculated that 26 coils would suffice to prevent the spring being coil-bound. After fitting this I noted, unsurprisingly, that cocking effort was higher but performance was hardly improved even after allowing for the new piston washer to form itself. Given this lack of improvement I removed the new mainspring and refitted the old one to give the easy cocking cycle.
Rebuild continued: Refit the cocking lever. With action in a compressor, add spring and spring guide, suitably lubed with moly, and the cage. With the drift in place, compress the spring until the holes in the cage and cylinder line up such that the cross pin can be replaced … but not yet as the trigger needs to be added. On some rifles that use this arrangement it is possible to add the trigger and return spring at the same time but I found this difficult: the spring is quite strong and the trigger is difficult to hold in place while the cross pin is inserted. So I installed the trigger first. The 3 sear parts on the trigger make it a bit fiddly but I used a thin punch to capture the sears as I inserted the trigger. Holding this in place I inserted a punch about the same diameter as the cross pin to get the sears aligned before pushing the cross pin through as it pushed the punch out. The trigger spring can now be replaced. This is best done with the action still in the spring compressor as you get more stability. I found it easiest to locate the spring on the dimple in the trigger blade before using a flat blade screwdriver to push the other end of the spring up and over the tang in the cage. Take care not to let the spring ping away. Remove action from the compressor and replace the end cap.
Replace stock and test. I had not increased performance from the initial test but at least I knew the piston washer was now OK.
Cheers, Phil