Friday, 20 September 2013

.177 SMK B45-3 Multi Pump Air Rifle- changing the seals.

It's cheap, It's cranky, it's made in China, Yippy! It's SMK

Mmmmm different.

I know it's been ages since I last wrote a blog, and believe me when I tell you this one took ages to write when I finally got around to it. So sorry for that, and I hope you find this as useful as I did working on it.

SMK B54-2 multi-pump with 4x32 scope

Oh the joys of owning a multi-pump air rifle, after learning all the ins and outs of the wonderful .22 Sharp Innova I am totally hyped up over this now obsolete SMK. The only info I have found online is a couple of YouTube entries by 'Weapons Collector' and a couple of sales spread over the last 8 years. So now I can put in my 10 pennies worth to this cheaply made Chinese air rifle.

Two screws that connect the stock.

The action is held to the stock by 2 flathead screws, one on the front of the trigger guard and the other onto the support mount for the compression tube and barrel that holds the rear sight.

Incomplete but still working rear sight

 The stock is made from some awful wood and coated in thick lacquer, it feels as light as balsa wood but is obviously a little tougher.

Not the best woodwork really.

 The trigger and sear is all in one and the spring to support it is set into the stock , however as direct sears go on explosive valves it is not too heavy a pull. However the trigger is very thin and could do with being a fair bit wider.

Trigger with it's direct sear

The ball bearing between the barrel and the loading port will mangle the heads of the pellets if you don't twist the mag anticlockwise, and will end up blocking the barrel up, so you can get away with loading 10 safely into the mag and load the way suggested. 

Ball bearing would be below the loading port in this pic.

To remove the back of the action, first remove the long screw that holds the metal lug that supports the spring against the sear, then remove the two grub screws that hold the rear of the action to the compression tube, and then remove the bolt and pin.

Long screw that retains the lug at rear, and one of the two screws that hold the rear action to the compression tube just below the loading bolt.

 The retaining lug, spring, and sear now slide out of the compression tube.

Lug, spring, sear, magazine with ball bearing, and spring above that.
Ball bearing which can go flying!

It's important to hold the magazine back to the front action as you work the rear action off, as the spring holding the ball bearing for rotating the magazine will go flying.

Bugger! where's that thick washer gone?

Out comes a thick black nylon washer, then using small thin nose pliers I unscrewed the collar that holds the firing pin housing in place.

Washers replaced with O rings.

                                                                                                                Originally, rubber washers were used to seal the firing pin housing as all the threads and seatings were set into the compression tube. These were old and crumbling and were one of the reasons it didn't hold air.

Valve parts fit into here.

 Having recently purchased a large set of metric O rings, I decided to replace them with rubber O rings.

All the pieces from action, valve, and sear.

 The collar screw presses the O ring against the firing pin housing and a seal against a shelf, which then supports a spring that holds a thick rubber washer against the inlet valve for the pump.

the little silver screw on the bottom of the front action that holds the firing pin housing in line.

The firing pin housing is held in place with a screw through the bottom of the action so it lines up correctly with the transfer port. There is a corresponding screw hole on top of the barrel housing.

Firing pin housing with hole that lines up with transfer port, this runs straight through the housing.

 This gives access to the transfer port which needs no seal due to two seals either side of the firing pin housing.

washer removed to show O ring seal and firing pin.

 There is an O ring supported by a metal washer in the firing pin housing, sealing the pin. 

Metal disk with nipple holding broken seal.

With the firing pin housing now sealing the valve chamber, there is a spring that clips onto a metal disk, with a nipple on the other side that a rubber washer clips onto. This presses against a raised collar in the valve chamber and acts as an inlet valve.

Some inlet valve seals that didn't work.

The original rubber washer was utterly mashed up, so I made a new one which only lasted 30 shots before the raised collar cut through it. I tried again with something thicker and harder but again it got cut through. Most recently I've used harder rubber with an O ring glued in place so it seals on the outside of the raised collar. Fingers crossed this should hold!

 Now, down the pump end there is one butt ugly pump arm, and the components of pump mechanism are made of delrin or some such material, though the pump head itself is in pretty good condition. Adjustment was easy once I tapped a pin out of the pump head holder and screwed it out. A small retaining nut holds it in place to stop it from moving.

Rubber pump handle can be a bit of a finger pincher.

There is some side to side play in the pump arm itself but this is only minor, besides, you only need about 6 pumps to get 11 ft/lb.

There is a whole load of stuff I could do to this air rifle as it is pretty accurate with a scope on it, I was pretty impressed considering what I have experienced from old Chinese air rifles before. There's also a lot to play around with to improve it to my own tastes, so when I get around to some i'll let you know.


Best wishes, Wing Commander Sir Nigel Tetlington-Smythe 



  1. This is an Interesting air gun, Thanks for posting the pics.

  2. Thanks for the info , I have one of these on my knee as I type which didn't impress the wife but then again Ive had this rifle longer .

  3. Hope you found it helpful, they're wicked little rifles once the problem with the air inlet seal is sorted. It's a good job it's so quick and easy to strip, as i've lost count of the amount of times i've done it to date.

  4. Can you email me a detailed diagram of how to fully strip and rebuild one of these, preferably with some instructions,
    Also where can I get parts for one of these,
    My brother took my dad's gun apart and forgot how it went together,
    My email address is Thank you

  5. Hi Dave, if you hit the 'SMK B45-3' on the labels at the bottom of this entry, you will find every blog i have done this air rifle to date. there are picyures of exploded diagrams and detailed instructions between them, all the screws are flat head and a common metric size and you can buy a rubber O ring set for a fiver off Ebay that will cover all seals (including the breech seal, as the barrel can be removed to replace it, but i will be doing a blog on that shortly) apart from the rubber inlet washer seal (which you can make yourself with a thick rubber inner tube and a sharp knife or sissors). If you enter 'SMK B45-3 images' into Google you will get a better quality picture of the exploded diagram, as i just took a photo off the computer screen for my blog entry. I will try to Email you but i am snowed under with family and work at the moment. atb

  6. Hello
    I'm after a bit of help/advice on a b45-3
    It seems you are the only person who knows anything about them.
    I have acquired a delux model, which doesn't seem to had much use.
    But it won't work.
    Having taken it apart, all parts are present.
    I am new to pump ups, and this is my first one.
    Should the firing pin slide easily inside its housing ?
    And what primes the trigger?
    It seems to hold air, but won't release it, and there is nothing at the trigger.
    If you can answer these questions , I would very grateful

  7. this rifle has an exhaust valve very similar to that of a sharp innova, the sear is circulaar and held back by the one piece trigger. When the trigger is released the sear shoots back and the firing pin follows it, this then allows compressed air out of the chamber, up the transfer port and merrily behind the pellet through the barrel.

    If you are ever near Cirencester i would be more than happy to look at it for yor you, but this blog entry is only one of five on this air rifle, so i hope the others might help you along your way of being the proud owner of this lovely SMK multi pump (i love this rifle, if truth be told). I hope hope i have made it clear in my blog entrys that this rifle is a labour of love. Failing that, e mail me.

  8. ill keep this short as i can.
    drill the ballbearing hole out to 8.5mm and replace original ballbearing(7.5mm) with a larger 8.5mm ballbearing. does less damage to tips of pellets and makes turning the pellet holder easier. everything is .22 untill the barrel. simply swapping the .177 barrel for a 12mm od .22 air rifle barrel and drilling the new transfer hole.