BSA Mercury Rebuild

I think the BSA Mercury is a beautiful looking air rifle with the way the trigger block curves down from the back of the piston cylinder to meet the wooden stock, The chequering on the pistol grip, The short cocking linkage slot in the fore stock, and the slightly raised cheek piece. That's why i thought it would be a good idea to get her back to her former glory, so with a Titan XS main spring, piston washer seal, and a breech seal from J Knibbs i was on my way. 

This air rifle was given to me with a severe bend in the barrel at the breech block where it had obviously been fired with the barrel left open though this was an easy fix with a vice and a metal tube, and the forks that held the breech were very loose which again was fixed with the use of the vice. Also some one had put a spring from an SMK B2 in it and the breech seal was worn, which is what shall be adressed in this blog

BSA Mercury ready for working upon.

I removed the stock by removing the two cross head screws on the fore stock then the long flat head bolt at the bottom of the pistol grip, this is recessed into the grip and runs diagonally through the grip and screws into the trigger block.

Stock removed, note the long bolt that that goes through pistol grip.

To remove the trigger block i held the compression tube tight in a vice using leather to stop the vice scratching and gouging the cylinder, then there is a hole above and in front of the trigger guard in the block which an iron bar is inserted to give leverage in unscrewing the whole unit. As it came to the end of the thread i pressed a large block of wood behind it to stop the preload on the spring sending the trigger block flying,as it happens there was only two inches of preload which felt quite loose and the trigger block was  caught safely.

The hole in the trigger unit above and in front of the trigger guard is for using an iron bar for leverage

Then the cylinder, breech, and barrel were taped into the spring compressor to have the cocking linkage, spring, spring guide, and piston removed in a tidier enviroment than the work shed, basically the dining table in the kitchen

The spongy two inches of preload of the old spring.

The spring guide slipped out with two washers at it's base, one for supporting the spring and the other goes between the back of the spring guide and the front of the trigger unit. these keep the guide straight as the piston rod needs to pass through the guide and into the trigger unit, there it connects with the sear in the trigger unit which i had wrapped tape around to stop any pins falling out. Then the old spring came out, which seemed okay but the whole of the compression cylinder was in need of cleaning and lubrication.

The cocking arm linkage is articulated and once the cocking linkage guide and screw pin that connects it to the breech were removed, could now be removed and the piston could be slipped out the compression cylinder. The guide is held on to the cylinder by two cross head screws and holds a plate in place against the cylinder for the cocking linkage to slide against, it also has two tabs that fork out either side at 90 degrees for the fore stock screws. Where it connects to the breech there is a spacer washer that keeps the two walls of the linkage firm and tight, this is an easy one to loose if your not careful so i kept a watchful eye and it fell into my hand as i removed this end.

Old crumbling washer on the piston.

The piston head is held on to the piston body with a pin and a washer keeps the whole assembly firmly in place, but in this case the washer was well squashed and crumbled apart when the piston was removed. So i removed the the O ring piston seal and  cleaned all the parts with wet and dry and white spirits, then OOOO wire wool and white spirits , then with some kitchen towel i dried it out and removed any crud, and finished off with a final polish using Autosol on any parts that make contact with the compression cylinder.

Piston head and body cleaned and polished showing the holes for the pin

Luckily i had some tap washers that would fit the piston if i drilled the middle out to 10mm, however one was not thick enough and two was to thick.

Making the replacement washer

So i drilled out one and slipped it in place the after drilling another i managed to grind and file it to the correct thickness, so in the end one and 1/3  was just the right thickness to replace the washer. Some people have gone without the washer and drilled a new hole at 90 degrees to original hole further back,you have to grind down the end so the piston head fits but this does give you a tad more swept volume.

The new shiny smooth O ring seal below with the old tired one above.

The replacement O ring seal slipped into place on the piston head easily, comparing the old and new one showed me the original was worn and had streached with time and use.

I removed the compression cylinder and filed away any sharp edges, then went through the same cleaning and polishing routine i used on the piston.  Though this time all the materials  were clipped on to a slit in the end of some 6mm aluminium tube and wrapped around the end so i could get right down to the transfer port, looking at this made me think it quite a small diameter for a .22. The whole of the inside of the cylinder was shining bright when i had finished as i spent much more time and effort doing this part, it was then taped back in place on the spring compressor with some blocks at the breech support to bring the end of the cylinder over the end of the compression tube bed.

The preload of the Titan XS  spring, all 34 coils of it. In the fore ground is the old SMK spring.

The new Titan XS spring has 34 coils where as the the old SMK spring has 31 coils and was compressed a fair bit, this presented me with over four/five inches of preload which would surely test my DIY spring compressor. Also the curved shape of the trigger block meant that the end was off center for the threaded bar on the compressor, this was sorted by building a housing from two pieces of wood and some metal sheet. With the trigger block in this jig i could compress the spring while presenting the trigger block to the cylinder at the correct place and angle, once presented half a turn once the threads started to bite would hold the trigger block to the compression cylinder. Giving me time to remove it from the spring compressor and screw it into place with the use of the iron bar, though the last bit would need for it to go back in the vice and finish off screwing it together.

Trigger block in it's jig and compression tube just hanging over it's bed. I had to compress the spring by hand a bit so it would fit in the spring compressor.

Applied Abbey SM50 to the O ring seal and some Abbey LT2 grease to the last inch of the piston,then this was slid into the compression cylinder. Followed by the spring with both the ends polished, i had dabbed LT 2 grease over the front half of the spring then taking a cloth i spread it thin and evenly by wiping down and around the whole length of the coils, then LT2 grease was applied to the ends or the spring and the outside of the spring guide and both washers. The jig supporting the trigger block was lined up and placed  behind the rear washer with the threaded screw bar of the compressor directly on the back of the metal sheet at the back of the jig, this would allow me to turn the trigger unit 180 degrees when the spring was compressed enough so the threads would bite.

It took a couple off attempts to get it right in the end, and the spring compressor held together with the force of all the preload though i could see the poor thing staining. Once it was together the articulated cocking linkage was greased at the hinge, at the breech block on the screw pin and spacer washer, and on the tabs that go into the cocking slot and moves the piston so it cocks. The metal plate was slipped under the cocking linkage and the guide screwed back onto the cylinder, and then the stock was screwed back on leaving only the breech seal to be replaced.

When i cocked the gun i could straight away feel the extra effort needed for the new Titan spring but it was still easy effort, linkage and internals moved smoothly and made no noise. Putting a Wasp No 2 pellet into the breech i locked it back an took a shot, there was no twist or kick to speak of as the piston slammed home which was a definate improvement. I will have to knock up a slip washer and top hat in the fonley lathe when i get some delrin bar, but for now its just a matter of prising out the old breech seal and pressing the new one home.

I did have a lot more pictures for this blog but before i had chance to move  them over the computer stopped working, so it had to be re booted and anything put on since it was last saved two weeks before was lost. But some were moved over to the blog before this happened so it wasn't a total loss, any way i'm sure i'll be coming back to the Mercury some time in the future so i'll get some better pictures then.

TTFN

Wing Commander Sir Nigel Tetlington-Smythe. 

   

  

Sharp Innova Breech Repair

Now the Innova is shooting fine and holding air i should at least get get her looking good, and that chip off the back of the breech is not only a spoiler but doesn't allow the bolt catch spring to stay in place. I decided at first to shape a  piece of  8 mm flat bar aluminium and screw it into the back of the chipped section, but first i would need a flat surface to attach it to. For this i used a small circular grinding stone in my Dremel, which is actually made by Draper but i refer to it as a Dremel anyway.The surface was now flat and flush with the back off the bolt catch.

Aluminium plate that held the spring for the bolt catch , after grinding a flat surface.

However i discovered that the bolt i used to attach the piece of shaped aluminium bar was to long and it would press against the sear, so after a shot it would stay in place and let the firing pin move when i gave the rifle a pump. So i cut the bolt shorter and added a drop off abbey SM50 to the sear, now it dropped back down to the firing position and the valve held air again. i used a cut off piece off spring from a clipper lighter to hold tension on the bolt catch, then screwed the shaped aluminium to the flat surface.

The breech is made from a plastic and seeing as i make dread beads and stuff out of Fimo modelling plastic clay, maybe i could shape some Fimo while pressed against the space left by the missing chip then bake it. 

Cardboard in place to stop the Fimo from hindering the bolt catch movement.

 I would glue this with Locktite and drill a hole so the bolt would hold it more securely as well, i cut a piece off thin card board to place over the aluminium and around the bolt so i could not press the fimo to far and impead the bolt catch.I placed the aluminium bar under this then pressed the Fimo into place and shaped it  a little over sized, as i could  grind the Fimo after baking and fitting it so it would be flush with the rest of the breech.

Molding Fimo onto the back off the breech.

Pulling the soft fimo off the back of the breech i cut a notch for the the bolt pin on removal then popped it in the oven and baked it, i left the aluminium in the Fimo so i could drill a matching hole for the bolt.

ready to be drilled after coming out of the oven.

Fimo takes 20 minutes to bake hard at 100 degrees C  and has a little flexibility while still warm, so I quickly drilled a hole and a larger one to countersink the bolt screw on the outside surface. Dabbing a few spots of locktite on all the surfaces that needed joining, i removed the card board and pressed it firmly into place and held it there. Once the loctite had set i put a spot of it on the bolt screw and quickly screwed it into the countersunk hole and breech.

Fimo baked , glued, and screwed in place prior to grinding flush with the breech.

 After leaving the whole thing for 20 minutes or so to harden properly, the fimo was ready to be ground so grinde away i did,so now i'm left with a breech that looks the right shape.

Finished article with breech repair after grinding.

So now i have a complete Sharp Innova short of the rear sights, which i was given but i'm buggered if i can remember where i put them. Besides i dialed in a solid generic 4x32 scope at 12 and 25 yards on 5 pumps and it is so accurate that this one is going to be a keeper, besides i wouldn't get top money if i sold it because of it's original state and my repairs.But they are solid and good enough for me, i would recommend that if someone wanted a multi-pump that they should get one of these. I mean , Sharpsman on airgunforum has loads of Sharp Innova's and he swears by them, if your really lucky he might sell you one, but i doubt it.

These multi-pump air rifles are solid, accurate and a wicked design, it's a shame that no air gun company has taken this 1970's design any further.Webley now do the Rebel which is pretty much the same air rifle. But so far it has only come in .177 and has about 3 sets of ft/lb limits. So you better make sure which one you order or buy, and though some parts actually have Sharp printed on them i'm not too sure if parts are interchangable or if the valve is of the same design.Yeah Man , get a Sharp Innova, it could do with a raised cheek piece on the stock so your head is comftable with a scope. Mine is .22 and i can get pellet on pellet at 40 yards,these air rifles are the dog's bollocks to be sure.

I'm waiting now for some parts from J Knibbs so i can finish off working on other air rifles that i have already start writing the blog for, so it won't be long before some new blogs on some lovely springers will be on there way. 

During the repair of this air rifle i was mostly listening to Heavy Horses by Jethro Tull, Thank Christ For The Bomb by the Groundhogs , and Safe as Milk by Captain Beefheart.

TTFN

Wing Commander Sir Nigel Tetlington-Smythe   

Sharp Innova Dissassembly and Reassembly, Saved From The Dustbin

For a more detailed look at the Sharp Innova check out my more recent blogs '.22 Sharp Innova a restoration project' HERE  HERE,  HERE , HERE, or HERE

In my last order from J Knibbs  i decided to see if i could resurrect the Innova and got the complete seal and washer set, and a replacement pump head seal. With the back corner of the breech block chipped off exposing the bolt catch and unable to keep the spring in place, I wondered if it was beyond repair at all. But when I pushed the catch up and it held the bolt I thought why not, besides, I could always attach a small plate to hold the catch spring in place or something. But first sort out the valve as it would only hold under one pump of pressure which would slowly leak out, it sounded like the inlet valve was broken but it had to be taken apart to see. I had heard good reports about how good these Japanese Multi-pumps were, dispite all the plastic used to make them.

Step one was to open the pump arm all the way open so no air was compressed in the compression tube, this makes it a lot easier to remove the pump rod unit. You can remove the pump cylinder and exhaust valve without taking the front end apart, but i decided to dissassemble it so i could clean and polish as much as i could.

front hollow pin, though the photo was taken when i reassembled

I tapped out the front hollow pin which holds the front unit to the compression tube, i then removed the hinge pin next to it. This is held in place with a circlip and holds the pump arm and the front unit inside the compression tube, it is made of solid plastic and could now be slipped off the tube, inner barrel, and plastic outer barrel.

Pin holding the underlever to the piston rod unit coming out through the hole for the pump arm pin

With the pump arm removed i could pull the piston rod unit back and disconnect the underlever, tapping the connecting pin through the pump arm hole. The pin does not line up perfectly with the cylinder holes, with one side lined up 3/4 of the pin was visible on the opposite side and needed a smaller pin to tap it out. The piston rod unit could now come out easily, not only did i need to replace the pump head seal but the rod was in need of straightening out a little. There was adjustment at both ends of the rod, so after clamping the rod in a vice for half a day to remove some of the warp i made some adjustments to lengthen the pump rod unit.

 The brass hinge end was given two complete turns after releasing the locking nut and then locked back again, and the seal end was given three complete turns again with the locking nut to secure it.So now to get to the exhaust valve in the compression chamber inside the breech, I thought removing the stock would be a good idea for a start.

Brass collar in front of the trigger with the grub screw square nut set in the breech housing in front of that

By removing the front crosshead screw on the trigger guard the stock was removed revealing a brass collar, which i unscrewed to reveal a screw thread sticking out of the breech unit, this has a slot for a flat head screw driver and secures the valve in the correct place in the compression tube. In front was a grub screw which goes through a square bolt in the receiver body to press against a metal spacer which forces the compression tube upwards in it's hole in the receiver, which has a tad larger diameter. This seals the tube and valve to the barrel, but unfortunately no spacer  slipped out when the screws were removed as it was missing. Anyway the compression tube came out easily with the breech seal O ring in place, the O ring was put aside and the new one from the seal kit was sized and made ready for when it was reassembled.

Transfer port O ring seal sitting between the compression cylinder and breech unit, no spacer though.

Getting the exhaust valve assembly out was pretty simple with no pump arm still attached to accidently close and send parts flying out while dismantling, i made this mistake a while back much to my regret. The exhaust valve back guide was just under finger tight and unscrewed easily but only the exhaust valve spring and the spacer sleeve came out, there was no bumper or bumper plate but luckily these items came with the seal kit. Pushing a piece of dowel down the front of the compression tube the valve unit slipped out the back, if the pump arm was still connected you could slowly close this to push the valve out.

Valve air chamber and guide with firing pin, spacer, exhaust valve spring, and exhaust valve back guide

The valve unit consists of the brass front end air chamber screwed to the brass valve guide block with an O ring to seal them, when unscrewing them its best to be careful of the valve spring that holds the inlet valve ball from flying out. Stone me! They were hard to get apart, in the end i had to use two sets of mole grips and twist them because they were joined so tight. The mole grips left marks on both parts, but i sanded them down with some wet and dry till the were smooth. Now i could unscrew with my fingers and carefully caught the spring and ball in my palm and put them aside, i teased the old O ring out with small flat head screwdriver after sliding the firing pin out. I removed the small brass collar and the firing pin O ring seal from inside the guide, cleaned the brass parts with white spirit, put in the new O ring seal with a spot of Molicote and brass collar, then put on the new valve O ring, and put that aside ready to screw back onto the air chamber.

The air chamber itself Has a delrin seat for the inlet valve that is held in place with a screw in collar  and is a guide for the valve spring, it has two slots opposite each other at the top so a flat blade  would unscrew it. Shining a torch down the chamber i could see small nicks on the delrin seat explaining why it would not hold air, there was no replacement delrin seat but i then i noticed an unaccounted fat do-nut O ring in the seal kit that would fit perfectly in the hole for the collar to sit on. So i unscrewed the collar and teased the seat out with a pin from the outside of the air inlet hole, removed the outer seal, and cleaned all the brass up with white spirit. Putting it back together was a case of popping in the new do-nut ring, screwing in the collar to seat it comfortably, cleaning the ball and dropping it in place with the spring on top, then screwing the guide back into the air chamber so they joined but were not over tight. Problem sorted hopefully.

I then cleaned the compression cylinder with OOO wire wool and white spirit on the end of a piece of dowel, then polished the chamber with autosol as i don't have any GN paste. I slid the bumper on the longest side of the firing pin and pushed it against the collar in the middle, the other shorter side was smeared with molicote and inserted into valve guide. Making sure the transfer port and screw hole were lined up correctly i put a smear of molicote on the O ring and inserted the valve into the compression chamber until the holes were aligned, in went the exhaust valve spring followed by the spacer with the new bumper plate snuggley fitting inside the rear,and finally the exhaust valve back guide was screwed back in less than finger tight into the rear of the compression cylinder so it was flush with the firing pin.

I smeared a touch of molicote to one side of the transfer port seal and put it in place, then with the trigger pulled back i inserted the cylinder into the hole in the breech leaving space between that and the barrel to keep the seal seated. The hole for the theaded screw was lined up when the exhaust valve back plate rested against the sear and then it was a matter of screwing in the thread and the brass collar over that, then placing the square bolt in it's space in the breech i screwed the grub screw pushing the compression cylinder nice and tight against the under side of the barrel and sealing the transfer port. Now with the cylinder in place i reattached the stock with the crosshead screw in through the front of the trigger guard and into the brass collar on the breech, i was left with four small O rings which were two bolt seals each in .177 and .22.

 Taking the pump rod unit i removed the pump head seal by working it side to side and pulling, it was a black delrin type material with a flat face slightly raised around the outside with a pin size hole in the center and pretty worn all round. The replacment was of the same material but was orange, it had a flat face with a parachute design around the outside which i imagine would leave a little more compressed air before the inlet valve. It was hard to press it into the pump rod unit by hand, so i placed it face down on a clean flat surface  and tapped the pump rod unit with a rubber mallet till it fitted in place. I smeared three or four drops of Abbey SM50 arond the pump head seal and pushed the unit up the compression cylinder, and put every thing back together by reversing all i did to when i took it apart making sure to oil the hinges and grease the pins as i did it

Sharp Innova restored to working order

I gave the innova four even pumps which became increasingly harder, but were still little effort by the forth pump locking and unlocking smoothly at the end of each stroke. I loaded a .22 RWS Superdome into the breech, which for its size and with a 4x32 scope mounted on medium Hawke mounts is surprisingly easy to do and squeezed the trigger. Luckily the pressure of the bolt sping pressing the bolt  against the bolt catch kept the catch in place, but this is not at all reliable and needs sorting. The rifle fired with a low to medium crack and the pellet hit the target board from 27 meters with a hard and loud whack, much louder than one from my .22 HW35 or .22 BSA Mercury sounds at the same distance.

 I can confidently say that this rifle certainly has the minerals, it just needs the missing parts replacing, and some thing done about the chipped off piece at the back of the reciever. I'm sure i can make these parts myself or at least the bits i've mentioned so far, because it also appears all the parts for the trigger adjustment are missing and i have no idea what they look like. Anyway these are things to do next and will without doubt become future blogs, and i'll be sure to take more photo's in future so it'll be easier to understand.

TTFN

Wing Commander Sir Nigel Tetlington-Smythe