To disassemble/assemble the retractable butt stock see HERE.

To disassemble the butt stock of a G3 type rifle*, you need to remove the butt stock end cap first.

Then you unscrew the three screws (yellow colored) from the buffer and that is all there is to it.

 

 

How to remove the end cap.

Place the butt stock end cap in a vice and pull apart (It may help to wiggle the stock a little whilst pulling-click to see animation).

Put some cardboard or similar between the jaws of the vice and the butt stock end cap to avoid scratching the end cap, and do NOT over tighten the vice.

 

*Please note that there are some types of stock that disassembles in other ways than this, or not at all. Examples are the later type HK33/MP5 stock which doesn't disassemble, and MSG 90, PSG-1 and also other produces than HK or HK licensees, e.g. Cetme.

Note: You do this on your own risk, and if you somehow manages to break or otherwise ruin your stock, well that is your problem. If you are not 100% sure about how to do this, don't do it, or pay someone competent to do it for you.