The BSA Scorpion is a monster of an airgun pistol; in the 70's and 80's it was the most powerful around.

You may consider this a niche Instructable.

I bought a secondhand one in a private sale online.

I had never seen one in real life but I was fascinated by what I had read; when it arrived I laughed out loud; it's massive.

The reviews praise it's power and accuracy. (for targets only, not for vermin control).

I could not find a pictorial strip down guide anywhere on the internet, so here is my own.

Any improvements corrections or tips are welcome.

The exploded diagram is from the Chamber air gun spares site.{ I have modified it a little).
They supply a good range of spares for vintage air guns.
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Step 1: Tools.

You will need:


A small flat head screwdriver.

A Posidrive screwdriver.

A 3mm Allen key.

A slotted tube         ( using a bicycle seat-post; this will be explained in the guide  )

An improvised spring compressor     ( using a sash-clamp; this will be explained in the guide  )

A wooden dowel.

Parallel punches ( you could get away with it without them)




A breach seal ( if needed )

A buffer washer ( if needed )

A piston seal ( if needed )

Step 2: Removing the grip.

Firstly unscrew the bolt holding on the safety catch and remove the catch.
There is catch on the heel of the grip

Very carefully push a small screwdriver into the opening.

Study the photos; the aim is not to lever open the catch but to release the little arm that holds the catch on.

Once removed you can see how unusually delicate this component is for such a hefty beast.
Inside you will see the head of an allen bolt. 

Undo this.

At the rear underside of the pistol is a silver posidrive screw; undo this.


Carefully pull the grip away. 

It is much lighter than I thought; not solid plastic.

i have a question , i wanted to rebuild my bsa scorpion , i change the piston for the new stainless one , and when i finalised the reassemble , they not cock .

So i probably make a mistake somewhere , when i install barrel's cocking system the piston and spring are like on your's step 5 second picture , piston is compressed in and i take the hinge or rod of the barrel and install it in the most forward possition as possible , and after that i install the trigger assemble . but nothing he not cock . do you have and ideal of what can wrong . thanks you

Thank you very much for this usefull guide .
I have a similar pistol , cal 22 and I can't refile the air stroke as it gets stuck after first step . Please advise how can I fix this.
Thanks alot for your time.
FriendOfHumanity (author)  mahmoudemad1 year ago
Dear Mahmoudemad,

I don't know how I missed it but I have only just just seen your question.

I'm not sure that I understand it; I am not familiar with the term: refile the air stroke.

If you mean that you cannot cock the pistol, then that may be due to the Buffer having disintegrated which causes the piston to seize. It has to be taken out, as far as I am aware, with brute force but by using softer than steel tools, eg that are made of wood, plastic or possibly copper.

If you tell me more I may be able to help but my airgun  knowledge is quite limited.

A site where you will get a comprehensive answer is ;
They have a section for general airgun inquiries as well as one for vintage airguns.

Good luck.