The Swedish Submachine gun CG m/1945 and the Sten are field striped in a similar way.
For this reason the field striping is shown here on the same page.

Remove the magazine and pull the operating handle to the rear to clear the weapon of any ammunition.

Pull the trigger and click the gun to let the bolt go forward on an empty chamber.

Depress the middle bottom of the receiver cap (buffer). 
Turn the buffer slightly counter clockwise and cap will come off.

See the drawing.

Remove barrel jacket and barrel

To reassemble, carry out in reverse the steps outlined above.

Depress the circular-shaped end of the reurn spring housing from engagement with the front plate of the butt, at the same time slide the butt downward from engagement.

With the thumb & forfinger, press the return spring cap about 1/4 inch and partiallyrotate it anti-clockwise, whereupon the two small lugs on the cap will disengage from their respective grooves in the casing. Remove the returnspring housing, cap and return spring. Pull the breech block rearward and remove the cocking handle when oposite the safety slot. Insert the cocking handle in front of the breech block and pull the breech block rearward until clear of the casing.

To Remove the barrel:

Disengage the barrel nut catch, which is located in front of the magazine housing, rotate the magazine housing anti-clockwise (downward), unscrew the cylindrical shaped barrel nut, and remove with barrel.

Unscrew and remove  the barrel by pulling the lock with a flat top beside the magazine support.

Carbine Machine Sten 9 mm. Mk.II, - General instructions, Feb. 1942  (Instruction manual from UK.)