Heanel Mod 1 DRP, Fixing and reassembly

Heanel Mod I DRP

Even though this air rifle was 75 years old there were still a lot of sharp edges on it, so I needed to get the draper mini drill out and deburr the compression tube. 

I thought it wise to clean the inside first as I didn't want to clean it with bits of deburred metal everywhere. It would also be nice to see if any damage had been caused by the nail that was embedded in the leather piston seal.

Hole left by the rivet in the piston face.

I used medium guage wire wool clamped onto and wrapped around the cleaning rod, it was dipped in white spirits and the inside of the compression tube was given a good all round scrub, and this was followed with a fine grade wire wool and then kitchen towel. 

Coarsest grade of wire wool removed most of the crud.

The inside of the compression tube was mirror smooth and shiny along the whole length, however some of the leather piston seal had stuck to the end of the tube, so I carefully chipped this off with the end of the cleaning rod. Now I could see that there were slight markings below the transfer port caused by the head of the nail, though these were nothing of concern. I did notice that the transfer port ran from the centre up to the barrel and by using the cleaning rod as a guide could see it was about 3 cm long.

White spirits stops most of the crud from collecting on the outside of the wire wool.

Using a craft blade I scraped the hard surface off the leather piston seal and shaved off any lumps and bumps off the face, 

A sharp blade brings life back to what appeared to be one knackered piston seal.

but not from around the hole left by the nail. Pouring some 3 in 1 oil into a milk bottle lid, I put the leather seal in to soak for a few hours.

Soaking in 3 in 1. A red plastic back plate give a flat surface for the leather seal to sit on.

When it came out, I placed it on a kitchen towel to soak up the excess, then pressed hard against a table surface. 

Remove as much excess oil as possible, it's going to smoke for a while as it is.

The seal appeared to have a new lease of life and a compression test proved there was new life in it now. Leather seals need a quick push to start to seal the compression tube unlike O ring and parachute seals which will seal straight off.

One restored leather piston seal.

I deburred the cocking slide and the pivot pin holes from the inside of the tube, 

Still has sharp edges after 75 years.

then screwed the grub screw for the barrel lock bar right in and deburred any metal created by the cocking linkage. 

That grub screw should come right out now.

White spirits and kitchen towel were used to remove any metal grindings from the inside of the compression tube, then I used 3 in 1 oil on some 0000 wire wool and cleaned every external surface of the rifle while it was dismantled.

0000 wire wool and oil removes rust but leaves whatever bluing is left on the action.

Now the leather piston seal was soft with no excess oil when pressed. It was screwed back on to the piston body, then the piston unit was replaced in the compression tube. 

A polish and light greasing.

The trigger housing has enough spring tension to hold the main spring in place with its preload.

With some Abby LT 2 grease liberally spread over the original main spring and spring guide, they followed on behind. I could always order a new spring later and this one was still a lot stiffer than the length of spring I ordered a while back.

The original main spring.

The trigger housing inner sleeve was still well and truly spring loaded and with it lined up, I carefully squeezed the forward end into the rear of the compression tube. I then gently tapped the rear of the rifle against the floor until the inner sleeve was back in place. 

This shows how much spring tension there is in the trigger housing.

The spring tension of the sleeve was enough to hold the main spring under preload and with the aid of a screwdriver the holes were lined up, 

All lined up.

the trigger was lined up and the pivot bolt fitted. With the safety in the off position and the trigger pushed forward, I replaced the end cap. With the end cap lined up, the retaining pin was fitted, it required the aid of a hammer to drive it home fully.

That pin takes some effort to fit as well as remove, so bear that in mind if you have to do this.

This was finger tight as there is a cut out in the stock for it to fit in.

The grub screw that holds the barrel locking detent bar unscrewed easily now that the end of the hole had been deburred.

A fair bit of wear and tear on this grub screw over the years, but it was easily fixed.

The bar and spring were removed, cleaned, greased with a little LT 2 and put back, with the head of the grub screw in a little deeper so that the cocking linkage wouldn't damage it again. 

Detent bar and spring all cleaned up.

 With a little grease on all the moving parts, the cocking linkage was slipped through the bridge and slotted into the compression tube, 

Guide for the articulated cocking linkage and threads for the fore stock screws.

the unlocking latch and breech were placed back in the forks and the pivot screw was replaced followed by the locking screw.

The pivot bolt goes in so much easier with the barrel broken.

It was a lot easier to tighten the breech pivot screw with the barrel unlocked as if it was ready to load, and this was without a breech seal in place.

The old leather breech seal was well beyond repair so I resorted to my trusty box of rubber O rings, 

Leather breach seal well beyond repair.

I did not have a three mm O ring of the right diameter so I cut one to the right size and super glued the ends together. 

New breech seal made from a section of rubber O ring.

It was made a tiny fraction larger so it would sit in the breech under its own pressure, the breech was closed to push the seal all the way home and a perfect seal appears to be produced.

New rubber breech seal fitted into place.

With the rifle lubed and put back together, I fitted it back into the stock, using a screw driver to hold the trigger tension spring back until the trigger was in place for the spring to fit over the tab.

Easing the tension spring back to fit on the back of the trigger.

Then it was a simple matter of fitting the stock screws. Each screw was fitted loosely at first allowing the action a little adjustability in the stock. This way all the screws attached correctly and then were tightened up fully. There is nothing more annoying than tightening one fore stock screw all the way home, only to find the other side won't fit.

Rifle back together, i gave the stock a rub down with wire wool to discover some lovely wood.

All I need to do now is build or bodge some sort of rear sight, the original sight is a simple affair so should be easy enough to make a rough copy. The safety still doesn't work, but I have an idea on how to remedy that, and the barrel lock could do with a new spring behind the detent bar. Anyway, the rifle fires with some authority now for it's size, but I will have to wait until I get a new chrony to find out what power it is producing.

TTFN

Wing Commander Sir Nigel Tetlington-Smythe.


   

Longsroking the .22 BSA Mercury

After fitting a brand new Titan XS spring to the Mercury, I discovered that the recoil was a little fierce, so I thought it would be a good idea to take it apart and nip a few coils off. I also thought I would have a go at increasing the swept volume, as this had been recommended on some of the airgun forums I have read. As it stood, there was far too much preload, and when I fired it I could not follow through as the scope view bounced all over the place.


So there came a day when I had the house to myself, what better time to set about tinkering with a rifle! Out came the screws that held the stock on and the action was placed in a vice protected by an old glove.

Don't want to scratch the bluing any more than it already is.

Then I set about unscrewing the trigger housing with the use of an old metal bar.

Any old bar will do the trick.

Remembering the preload, I jammed a large heavy piece of wood behind the trigger unit so it wouldn't go flying through the shed wall when it came loose as I undid the rest by hand.

Just got to be careful here.

There was still a far too much preload. I could see 2 or 3 coils coming off this one.

That came off with some force all the same.

Moving back to the kitchen table to remove the guide rod, spring and piston. I first removed the cocking linkage guide so the the linkage could be removed from the piston.

As the cocking linkage is articulated, you can remove the guide to slip it out of the compression chamber with out removing the barrel.

Once the piston was removed, I could straight away see one reason for some inaccuracy - the buffer washer I had made up out of rubber washers had flattened and was rubbing along the compression tube. Just as well, that was the piece to take out to shorten the piston and long stroke the compression chamber.

Pin is out, piston head removed.

With the piston head removed by tapping out the pin, the washer was removed. Now I had to see how much of the front of the piston cocking rod had to be removed in order for the head to sit on the piston body.

See how much needs to come off the end of the rod.

It was no more than 2 or 3 mm as there was extra space in the piston head for the rod end to sit in, so a quick grind down on the lathe soon removed the excess.

After the grinding of the rod, mmmm shiny.

Next I took out the Dremel, (well, actually a cheaper copy made by Draper), which had the bits and bobs I needed to carry on with the job.

The Draper, which is cheaper than a Dremel, and the piston body after the rod has been shortened.

Using the Draper and a cutting disk, I then set about extending the cocking slot in the piston body, because with the buffer washer removed, the piston would slam into the cocking linkage if this was not done.

Extending the cocking slot.

I removed about 4 mm and smoothed it off with a grinding stone, making sure it was even so that both bars of the cocking linkage would connect with the piston slot. I thought it best that if I was shortening the piston by 4-5 mm that I should only lengthen the cocking slot by no more than that, that's how thick the buffer washer was.


Now I had to drill a new hole for the pin that connects the piston head to the piston body, this is most likely strongest if done at 90 degrees to the original.

Lining up where to drill hole.

I lined the head up with the body and marked off where the pin would go through. First I used the Draper to grind a center for the drill, then with a battery powered hand drill I started to drill a 3.5mm hole.

Grinding new hole for the pin.

I found I was getting no where fast as the post was hardened metal, however I did find some sort of metal grinding tool in the Draper parts and that did the trick nicely.

Strange grinding head that beat the drill bits.

The hole now completed and not crossing paths with the original hole, I tested it all lined up with a darts head, which it did nicely allowing me to tap the pin in.

The finished article.

With the piston completed, I applied the appropriate greases to the seal (abbey SM50) and base on the piston (abbey LT2), then inserted it into the compression tube which I had cleaned and polished up. With the piston fully inserted I tested to see if there was space for the cocking linkage, which when pressed flat along the compression tube was about 2mm.

It's dark in there, but there is a gap.

There would be more than this as there is a steel spring plate that holds the cocking linkage against the linkage guide, also the spring stops the linkage interfering with the mainspring.

Steel spring plate that holds the linkage up.

I have a belief that the preload shouldn't exceed the swept volume. This is not proven by me but picked up from articles i have read by people who know their stuff. So with this in mind I decided to remove 3 coils, which i did along with shaping the last coil on the mainspring.

With some Abbey LT2 grease smeared liberally over the spring, spring guide, and washers, the rifle was placed in the spring compressor along with the trigger bock, in the jig I had previously designed for it.

Parts back in line and greased up.

Titan XS are really stiff springs and even with 3 coils removed there was a fair bit of preload, so when the spring compressor started creaking and broke, I wasn't really that surprised!

Bugger! Broke the spring compressor!

I remembered it straining last time I worked on the Mercury and should have strengthened the screw housing then, but by supporting the trigger block and jig with one hand it still managed to work and I was able to give the trigger block that 180 degree turn so it would catch. Quick as you like it was out of the compressor and tightened by hand until the final touch, that involved the vice and the bar so everything lined up nice and tight.


With the cocking linkage slotted in and the spring plate in place, I screwed the linkage guide in place, then the stock and scope were finally fitted and the gun was ready to be tested.

Start putting her back together.

The recoil is nowhere near as harsh as it used to be, in fact it's quite pleasant to shoot now. I am finding that with using .552 Air Arms Diabolo fields, I can usually get sub inch groups at 20 yards with the odd flyer, though I am refining my hold again as I have been using pnuematics a lot lately and my springer shooting tecnique has slipped a bit.

Yet again I didn't get around to putting a top hat and slip washer in the compression tube and piston, but it seems to be performing very well as it is. Apart from the odd flyer which as I said is down to my hold, it is a mighty fine air rifle indeed and i'm pretty chuffed with the results so far.

I believe that the spring was too fierce and was causing too much air to choke at the transfer port giving harsher recoil. I have also read that some other people also increase the diameter of the transfer port when long stroking, so i'll have to see if it's worth doing at some point in the future. For now i'm going to be finding the best pellets to use with this air rifle, as these older British ones do have a slightly larger bore of 5.6mm.

TTFN

Best wishes, Wing Commander Sir Nigel Tetlington-Smythe.