.22 BSA Meteor Mk IV Reassembly

In a far flung corner of the kitchen, south of the bread bin and east of the kettle, just past the pile of battery chargers and assorted bike lights, sat the dismantled BSA Meteor. It sat there for a week and every time i made a cup of tea or dinner, i thought, i really should put this back together and get some pictures. So one day while i had a korma simmering away, it , the tool kit, and all my other bits and bobs got moved to the kitchen table and work commensed.

 The serial number puts this as a late model MkIV.

Even though this air rifle is about four decades old, general wear a tear had not removed all the burrs and sharp edges, so attaching a small grinding head to the Draper mini drill i gave the rifle a once over. 

Removing burrs from where the cocking arm is fitted.

Removing the sharp edge to the piston and compression tube cocking slot by gently running the grinding head along, 

Old air rifles still have a sharp edge on the piston as a rule.

and the edges and corners where the cocking arm goes in as well as the inner edges of the holes for the main spring retaining pin. 

Main spring retaining pin holes tend to need deburring to protect the piston seal.

Then using the cleaning rod with some white spirit on some kitchen towel i cleaned the inside of the piston and compression tube, i didn't want any tiny bits of metal dust from the grinding buggering up the O ring seal.

Clean the metal dust out of the tube and piston before reassembly.

The piston with the old O ring would slide half way down the compression tube with my finger over the transfer port telling me the O ring seal was very worn, 

With the old piston seal this is where the piston rested with the transfer port blocked.

so the O ring seal came off and a new one was sized up from the big red box of O rings. 

A slightly undersized O ring makes a good fit as a general rule.

 The inner diameter of the compression tube is 26 mm but a 3 mm thick O ring that size  was a tad to big on the piston, so going the next size down had the O ring fitting the piston head pretty snug. It was also a snug fit in the compression tube and stayed were it was when i tried to push it down with my finger over the transfer port, and took very little pressure to move the piston when i removed my finger from the transfer port, perfect!

With new O ring the piston stays at the top with the transfer port blocked

Applying a little Abbey SM2 to the O ring seal and some Abbey LT50 below the piston head and on the skirt,

A touch of Abbey SM 2 for the O ring seal.

A dab of Abbey LT50 (moly grease) for the head and skirt of the piston body.

 the piston was fitted into the compression tube with both cocking slots aligned. I cleaned the mainspring and polished the ends with the mini drill as it saves time and blisters,

Just a few of the many useful attachments for the mini drill.

 and applying a liberal amount of LT 50 grease and a a bronze slip washer to the end i fitted it in the piston. 

Bronze slip washer, main spring, and not too much moly grease.

The washer that sits at the end of the spring guide and holds the main spring is a little chewed up, so another bronze slip washer was placed between it and the main spring. With a little LT 50 grease over all surfaces it was put in the end of the main spring, i left out the 4 mm delrin spacer i had in it from last time. I made sure the washer was a tight as possible to the spring guide, as it slips down the guide and rests against a slight lip.

Spring guide, spring support washer, and bronze slip washer before a light coating of moly grease.

Placing the compression tube assembly in the spring compressor with the fitting tool in place the two inches of pre load was pushed back in, it needed a light guiding hand to get it past the end of the tube. 

Min spring removal tool will need guiding by hand as it enters the compression tube.

The spring guide stayed where it was and had to be teased up with a screw driver so the retaining pin would fit, it also aligned the retaining pin holes with the cut out in the special tool. 

Screw driver will clear the path of the retaining pin.

The retaining pin slipped in the right way around and pressure was released from the spring compressor, there is a little chip out of the shaped side if the retaining pin but it's not on a pressure bearing side.

 The pressure bearing side of the pin is on the undamaged side as the spring compressor is released.

The barrel had a crap home made delrin breech seal which was removed and cleaned, and a spare breech seal i had sitting in the spares box put in it's place.

New BSA breech seal is fitted.

 Over the years the pivot pin in the breech had worn the breech hole a tad wider making the the barrel loose and move in the forks, and the only way to fix this without replacing the barrel is to shim the hole.

A very worn pivot pin hole on the breech.

 I originally used a piece of bar the same diameter as the pin to hold a shim cut from a tango can in place in the breech when fitting the pivot pin, i had lost that so i used a piece of 6 mm wooden dowel which had swollen slightly to the .25 inch which is the diameter of the pin..The dowel was cut so it was the same width as the breech and a strip of shim also cut to that size, the shim was wrapped around the dowel and where it creased where it met the start of the shim it was cut. 

Shim material is rolled around the dowel and cut to size.

Applying a little spot of LT 50 to the breech hole the dowel with the shim around it was pushed in sightly. The detent bar and spring were greased a replaced, 

Moly grease the detent bar and spring

and pushing it down on the back of a chair the dowel and shim where pushed all the way in so they were flush with the breech holding the detent bar in place.

Dowel and shim holding the detent bar in place.

The forks had been bent out because the stock screws had bit into the stock and push the tabs below outwards by pressing against the breech, i had bent them back in the vice making sure i had something between them so as not to damage them. 

Pressure from a vice staightens out the forks.

With this done the barrel breech was very tight between the forks, slipping the breech behind the pivot hole upside down and flipping around so the holes lined up. Making sure the lightly greased pivot pin was entering the right way around through the left hand fork it was gently tapped through the breech with a rubber mallet, the pin pushed the dowel out the other side leaving the shim behind. 

The barrel is uncocked at this point so the pivot pin can drive all the way home.

When the pin reached the other fork the barrel was cocked making it easier to guide it all the way home, as i didn't want to knock the forks out of alignment again.With the barrel fitted the cocking arm was ground for sharp edges, cleaned, greased both ends, then fitted into the compression chamber, then the breech.

Fitting the cocking arm with a dab of moly grease at each end.

Getting on to the trigger i had noticed that a small bit had broken off that held the spring,it held but needed cutting deeper to make it more secure.

The trigger with a bit broken off it seems to be made of cast metal.

So a deeper groove was cut using the cutting disk off the mini drill, this also has a benefit by creating less tension on the trigger.

Cutting a lip to hold the trigger spring securely.

Now the sear could be replaced, followed by the trigger, then the stop pin behind that.

The fitting of the pins in the trigger assembly is reletively easy.

Now the action and barrel were sorted the plastic end cap can go on the back, the stock was attached by the trigger guard screw a little, then the guard was slipped in and the screw tightened by finger then finished with a screw driver.

I sometimes have to waggle the trigger guard slightly to slip it into place.

Finally the front stock screws had to have enough washers to make sure the forks weren't pushed out when tightened, ideally some sort of brass cup would do the job here.

The forstock screws are pretty knackered, but hold tight with some washers to stop them pushing the forks apart.

Seeing as the rear sights were missing i decided to fit the Rangeright 4x32 scope for testing, i dont know what it is about me and old BSA's but they are always missing the rear sights when i get my hands on them.

Ready for a trip to the woods.

That's the Meteor sorted for now, all i need to do is sight it in and see how it does. If all goes well with that then i might clean and oil the stock and put some enamel paint on the metal work, mind you i quite like the bare metal finish when it's cleaned, polished and oiled.

TTFN

Wing Commander Sir Nigel Tetlington-Smythe

.22 BSA Meteor Mk IV dissasembly

A bit of history

The Mk III and all three models of the MkIV are identical air rifles, the difference being that the Mk IV's were contructed out of poorer quality metal. The bigger and altogether different Mk VII is the final model to be made and is rated at 12ft/lb full power, though Mk's I thru VI are pretty similar and all produced about 10.5 ft/lb on a good day with the wind behind you. They were very popular as a first air rifle for larger youths and is still large enough for adults to use very comfortably, first appearing in the late 50's they have sold millions over the decades but recently the desistion has been made to close production. This tit bit of information informs us that there is not a shortage of Meteor's out there lying hidden waiting to be found and refurbished, though finding an old one with the rear open sights sill attached is next to impossible.

The story so far...

I picked up this .22 BSA Meteor over a year ago for a tenner, and believe me it was in a right old state.

Meteor after a quick clean over a year ago.

So i cleaned the metal work and decided to strip the enameling and apply some oil to stop further rust, 

The scope rail on the Meteor are a little shallow compared to a lot of other air rifles.

Top of the barrel in front of the breech

i also gave the inside a quick clean and lube as the buffer washer had disintergrated. 

No rust after storing for well over a year.

The forks are bent out a little allowing side play, 

Length of the cocking stroke.

this is common with most early meteors as the fore stock screws attach to a tab below the forks and will force the forks out when tightened up to much as the screws press against the breech block.   

Chewed up stock screws chewing into the stock, and a bloody awkward rear sight fitting.

The breech moved back and forth also, on closer inspection the breech pin was fine so the problem lay in the hole through the breech wearing wider against the hardened breech pin. 

The old breech seal originally crumbled out so i experimented with turning one out of Delrin, it was crap and didn't seal properly.

God alone only knows what other problems there are hidden away with this rifle, and the only way to sort them is fix them as they appear.

 Dismantling.

To remove the stock, first the trigger guard has to be removed. 

Trigger guard and a nice wide set back trigger, very pleasant indeed.

The screw at the back is accessable though the slot in the guard, this also conncts the stock to the rear of the compression tube.

You really need the right screw driver for this screw, though you can loosen it outside the guard and finish off with your fingers.

When the screw is removed the the guard is tilted out and slid out, as a tab holds it against the stock.

Simple trigger guard design, i like it.

Secondly remove the two screws at the front of the stock, and all the washers that have been added -or haven't as the case maybe. 

Added washers used to stop the screw pressing against the breech block.

These are the buggers that can force the forks apart when they have started biting into the wood over many years, i would imagine these screws get over tightened is because of the long cocking slot on the stock.

The long cocking slot needs the side screws to fit firmly, or else.

Then the stock comes away and is put to one side so you now get to the trigger assembly, which has to come out so the piston can eventually be removed.

Trigger assembly looks like this, useful for putting it back together.

There are three pins, One larger that pivots the sear, One smaller one to pivot the trigger, and another small one to act as a trigger stop.

The pins can fall out but usually don't, the rear stop pin is the usual suspect in most cases.

The pins can some times fall out, so be careful. However the are certainly loose enough to drift out with slight pressure from a small screwdriver, and this leaves you with a sear, a trigger, and quite a strong spring between the two.

Sear contact adjustment hex grub screw on the trigger, it rests against the trigger stop pin.

This is where i discovered that a bit of the trigger has snapped off, the part that secures the spring in place though there is enough left to just hold it.

And this is how it all should go back together, another useful photo to have for reassembly.

The plastic end cap can come off the end of the compression tube now so you can access main spring which is held in place by a washer and shaped retaining pin, the washer has to be pushed forward either side of the retaining pin. So a special tool needs to made which is easily done, i used a piece of metal pipe and an angle grinder.

The useful homemade tool for removing the mainspring, it really is easy to make.

Secondly the cocking arm needs to be removed from the compression tube, and the barrel needs to be removed for this

Remove the pin where the cocking arm joins the breech, so the cocking arm can slide back to allow the tabs though the wider part of the slot.

I decided to see how much play i had between the cocking arm and the piston when at rest, as it's possible to shorten the piston. The calipers gave me 7 mm to play with safely without the piston slamming into the cocking arm tabs.

Green tape marked where the end of the cocking arm rested with the breech closed, then open the breech till the cocking arm rests against the piston and measure the difference.

 The pin that holds the cocking arm to the breech drifts out easily enough, and is shaped so a rubber washer in the folded steel of the cocking arm pinches it in place and stops it working loose.

Note the shape of the pin and the rubber washer at the front of the cocking arm.

The breech pin drifts out easier one way than the other, and by breaking the barrel the detente bar and spring don't add to the pressure.

I placed the end cap there in case the detente bar shot out, there was really no need in this case as it turned out.

There is play between the breech and pin and it's the breech block, 

The shim i made over a year ago sat on top of the breech block, also the detente bar spring is a little worn but still useable.

though i had shimmed it before with a strip of Tango can and that fixed the problem.

The diameter of the breech pin hole...

The diameter of the breech pin which is the same as the hole in the forks, so that should tell me something.

Placing the prongs of the pre made metal tubing either side of the main spring retaining pin, the compression tube was put in the spring compressor and the retaining pin removed.

The retaining pin is machined to support the spring guide and washer, i had to prod the guide with a screwdriver to free it from the retaining pin.

  Then the preload is let off till the main spring is relaxed, and can then be removed.

A couple of inches of preload.

There was a couple of inches of preload, some of it was added by a delrin slip washer and a copper slip washer i had fitted before.

This is the spring it came with, it is a BSA spring though it may be a replacement for the original at some time.

Then the piston is removed.

Piston with hand made buffer washer and a worn O ring.

Usually at this point people can have a lot of trouble removing the piston because the original buffer washer on the piston has crumbled to dust, i had this very same problem when i first had the rifle apart.

Piston head assembly fits into a key hole slot on top of the piston body.

So i have already cleaned and polished the inside of the compression tube and made a replacement buffer washer, the rifle is also lightly lubricated already. Originally when i first took the internals out i used very fine grade wet and dry dipped in white spirits and cleaned the inside of the compression tube and piston assembly, this was clamped to the end of a rod so i could get right down to the transfer port. I followed this with OOOO wire wool then Autosol metal polish to give a highly smooth mirror finish, luckily there were no score or wear marks inside the tube.

Ali tubing with a slit down the end to act as a clamp, wire wool and white spirit cleaning a very dirty compression tube by the look of it.

A effective way to test the piston seal is to drop the piston into the upright compression tube while sealing the transfer port with your finger, if all is good the piston should stay put then slide down the compression tube when the transfer port is unblocked. If the piston needs a little extra weight to do this it's still a nigh on perfect seal, but if if it's a tight fit and needs a fair bit of effort to move the piston with an unblocked transfer port then the seal is over sized. One remedy is to put the piston and seal in a lathe and lightly wet and dry the seal till the fit is perfect, another is to put the rifle back together and put a tin or two of pellets through it till the seal sizes it self.

 With the Meteor the O ring piston seal was well worn and would slide freely halfway down the compression tube with a blocked transfer port, so in this state the air would only start to compress well after the piston was released severely lowering power.

Piston O ring outer diameter looks to be 26 mm.

O ring has a diameter of 3.5 mm.

Using the calipers i measured the head diameter and O ring diameter, when fitted the O ring is 26 mm and 3 mm in diameter so it's a good job i have a big red box of different size rubber O rings to hand. But this is where i shall leave this blog for now as it's gone on a fair bit, when i get all the photos in of fixing the problems there will be the next part.

TTFN

Wing Commander Sir Nigel Tetlington-Smythe