More Stuff on the SMK B45-3

SMK B45-3 after lots of messing about.

It's not the prettiest air rifle and i'm constantly replacing the air inlet valve seal, but for some reason I really like this cheap Chinese multi pump. It's simple to dismantle, which is just as well, because finding the right size and material for the air inlet valve seal has been an ongoing mission over the last year or so. Too thin and the sealing collar cuts right through it, too hard and it doesn't hold air. But with a lot of trial and error I have found something that holds a lot longer than the simple rubber flap washer I used originally. Now I use a thicker, harder rubbery plastic, found on a cheap head torch, which I cut to shape. It is holding up well so far.

A selection of different materials and sizes for the inlet valve in the centre of the picture.

The original stock and pump arm are butt ugly and so is the action if truth be told, but at least I can do something about the stock. I have made a new stock and pump arm which lends more weight and balance, and a raised comb making it a lot easier to shoot.

The trigger gets heavier the more you pump as it releases air from a dump valve/exhaust valve. It would be more accurate if the trigger was a lot lighter. And actually, the thing about this little rifle is that it IS accurate, that is why I have persevered with tinkering with it and will continue to do so. If I go down to the woods with an air rifle, this one always comes along. It is great fun for a plink on my permission woods.

Recently I had found that it was not as accurate as it used to be, so I had a look for the cause of this. On close inspection I discovered that the barrel was slipping out of the breech and that it was also moving slightly in the sight housing/support. 

The barrel loose in the breech block has shifted 2 mm.

The barrel has a thinner diameter where it fits into the breech and is held in tight with a screw from above, this screws into a hole that runs top to bottom which acts as transfer port, and a screw hole underneath for holding the firing pin housing in the right position. Some screws were missing when I got the rifle, and the screw that holds the barrel tight was one of them. I found a screw to replace this and turned it into a grub screw so it wouldn't clash with the scope mounts.

Brass grub screw that secures the barrel.

Once I had loosened the grub screw out, I found I needed to deepen the slot for the flat head screwdriver blade, then it was matter of tapping the barrel back to it's true position. 

Tapping the barrel into the breech while the front sight housing is attached.

The crown of the barrel is recessed so is hard to damage, so tapping it through the sight housing wasn't a problem. 

The barrel crown is not really the crown as the rifling stops 5mm into the barrel.

With the barrel back in place, I checked it was aligned by poking a small hex key up from underneath the breech with the firing pin removed; it was, so no adjustment was needed. Then the grub screw on top was tightened securely against the barrel, which, judging by how far it screwed in, was not secured before.

This was when I noticed that the barrel was not such a snug fit in the sight housing and would move around if I applied pressure from side to side. It was barely noticeable but it was movement all the same. As there is a barrel band, it is not supposed to be a free floating barrel, and a lot of force is placed around here through the use of the pump arm. 

Pump arm pivot pin and securing screws removed.

I removed the pump arm pivot pin and securing screws so the sight housing could be taken off, and replaced the plastic cone that fits over the barrel - i'd originally assumed this was there for an aesthetic purpose and had left it off. The barrel still had movement in it with the cone replaced, but it meant I could wedge a sliver of rubber between the underside of the cone and pump tube. 

Small piece of rubber stops the barrel moving about when using the pump arm.

This pushed the barrel upwards and stopped all movement.

The small cross-head screw that holds the pump arm pivot pin secure in the pump tube is not original, this replacement has the habit of working loose and letting the pivot pin move back so slightly, adjusting the length of the pump stroke. There was a marked difference in point of impact when pumped seven times with the pivot pin secure and seven times with the pin loose. So I decided to use Loctite thread glue to hold the screw in place, and this appears to have done the job.

This stuff really works.

I am happy to say that these small jobs have not only restored it's original accuracy, but have even improved upon it. If I could somehow make the trigger pull lighter the accuracy would be even better, as I have the tendency to pull some shots to the left with it as stiff as it is. But saying that, it wouldn't be too hard to build a replacement trigger for it, such is the simplicity of this rifle's design.

TTFN

Best wishes, Wing Commander Sir Nigel Tetlington-Smythe

.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