Clear magazine tube of cartridges then cycle action to clear chamber.
Remove inner magazine tube.
Leave rifle cocked and put on safe.
Unscrew action screw on left side of receiver and pull out, it can be turned to prevent it from sliding back into receiver.
Separate lower from upper by pulling apart.
Pump action to move bolt to rearmost position and lift rear of bolt to tilt front of bolt into clearance hole in top of receiver, then pull action forward to release bolt, pull bolt from action.
Action slide can be removed by unscrewing and removing the lock screws, then unscrewing and removing the forend retaining screws to free forend.
Action slide can be removed from rear of action by pulling assembly out from rear.
Forend will separate from action slide as the action slide is pulled free.
The little piece that falls out is the cartridge retainer, don't lose it, you'll need it later.
When replacing the cartridge retainer, the larger tab fits onto the barrel, the small tab fits in to the receiver, both tabs face up towards the barrel and receiver roof, the action slide is replaced and allowed to slide over the cartridge retainer and the magazine tube is pushed through the forend and barrel retainer ring(s).
Forend is then secured to action slide with the screws, leave action slide forward.
Replace bolt in receiver and move forward until front of bolt tilts into clearance hole.
Pull action slide rearward until it passes over front of bolt and allow bolt to then drop level.
Pull action slide forward, it should pick up bolt and move assembly into locked position.
Reassemble rest of rifle. HTH
