Welcome to my pictorial guide for the Tokyo Marui M3 Super 90 tri-shot shotgun. The instructions in GREEN are necessary for a take down (to gain access to the internals), the stages in RED are not necessary for access to the internals but can be performed for a complete take down into every individual part of an M3.  
Tools:                                                                                                   Optional:
-small phillips head screw driver (~3mm head)                                       -grease for reassembly
-large phillips head screw driver (~6mm head)                                        -small torch
-large flat head screw driver (~5mm head)                                             -barrel cleaning rod
-1mm allen key                                                                                    -needle nose pliers
-T7 torx type screw driver
                      Tokyo Marui M3 Super 90
This is what you should start with, the entire gun, unloaded, tools at the ready. Ideally on a flat, clear surface. I like to use a quilt to stop unnecessary damage to parts by working on a metal or stone surface. Wood is okay but I still use a quilt because pieces such as screws can't roll off and get lost. Equally speaking, don't use a surface like a carpet that is TOO fluffy, because fiddly bits will get lost in it. Ideally your surface should be white too (so everything is very visible). Obviously, if its white, make sure its something you don't mind getting grease stains on.


The Stock
Start with the rubber butt pad.
Peel it off starting at the bottom for best purchase, although some can be quite loose, as is mine.
Now use a large phillips screw driver for the main stock bolt.
Once unscrewed, slide the long bolt out of the rear. Take care of the small washer on it.
Now pull out the plastic inner plate.
Pull out the metal stock weight. It should be wrapped in some kind of foam to stop it rattling.
Push through the rear sling mount from one side.
Pull out from the other side once it is exposed.
It should look like this, put it to one side.
Now pull the stock away from the receiver.
It should slide right off the rear end.
To release the rubberised grip from the stock, locate the bolt shown here, inside the stock shell. Use a large phillips head
screw driver to undo it and be careful once again of the washer that should be on this bolt.
Then slide it down away from the stock.

Front End
Use a large flat head screwdriver to loosen the barrel clamp.
Then slide along the barrel to remove it.
Now remove the plastic mag tube end cap.
Pull it out and twist it either way to lock it 'out' like this.
 Use a small screwdriver or other implement to depress the nub located under neath the mag
tube - this will aid removal of a tight mag tube cap.
With the nub depressed, wriggle the cap out of the tube.
 Now unscrew the sling plate nut, no tools required, just your thumbs. Once loose, slide it off the end of the mag tube.
 Now the sling plate itself will be free to come off.
Remove it too and set these parts to a safe/orderly place - as always.
Now find the two short screws underneath the pump grip.
 Use a large phillips head screw driver to undo these two.
 Then find the gap at the rear of the right hand (gun facing forward) half of the foregrip.
Use a long thin flathead screwdriver to push inside this gap. 
For brand new and/or stiffer foregrip sets (that are harder to pry apart) you should also use a knife for extra purchase,
by slipping it in the seam between the two foregrip halves.
Lever away the right hand foregrip using the action of both the knife and the screwdriver.  
 Once loose pull it away and set it aside. 
 To free the left hand foregrip, remove the screw shown in the bottom of this picture below. 
Like so...
With the screw removed the left hand foregrip should almost fall off under its own weight, just slip it off and set it aside.
Remove the two screws at the top of this pic. Then flip the gun over and repeat for the other side.

Be careful not to lose the small washers which should accompany these four screws.

Now remove this screw on the plastic pump guide.

Then remove the opposite screw on the other side.

The plastic pump guide is now free to be slid forward (away from the receiver).

Slide it all the way out to reveal two screws on either side of the gun.
Remove all four of these.

 The entire front end will now be free to slide off the receiver of the gun.
With the front end removed you should be left with this. Note the black plastic cap on the silver inner
 barrels, this can fall off when you slide off the front end so if its not there, tip up your front set and shake until
 it falls out so you can keep track of it.
Slide the plastic pump guide rearwards along the mag tube.

You will meet resistance before it slides off the end of the mag tube, once you do, pull it downwards away from the barrel.

Now separate the barrel and mag tube. This requires the use of two actions simultaneously.


Firstly by sliding the mag tube rearwards (note the threads for sling plate nut have moved rearwards in this pic).


This is combined with the action of swinging the mag tube downwards also, shown here.

Then you will have the mag tube and outer barrel separate, slide the metal pump grip guide off the mag tube.

Like this...

Locate this pin on the threaded part of the mag tube.

Using a small screwdriver or other implement tap the pin out from the countersunk (recessed side).

With the pin removed, slide the threaded part off mag tube.

With the pin removed, the shell tube spring (which ejects shells stored in the mag tube) will fall out of the mag tube.

At the rear of the outer barrel on its underside you will find this mounting bracket, remove the two screws on it.

This will leave you with these parts, the bracket itself, the two screws and the silver coloured
 internal mount (note that during reassembly this internal mount should have the
 rounded end facing forwards - as orientated in the pic).
To remove the rear sight find this small screw on the inside of the outer barrel.
This rear sight assembly can be further disassembled. Use a 1mm allen key to unscrew the grub screw shown here. Then slide the rear sight blade sideways out of the rear sight base.
Remove the screw shown here (underside of outer barrel) to loosen the mag tube bracket. To remove it you need to swing it out 90 degrees forwards then pull away.
Find this hole in the underside of the outer barrel (at the very front - below the front sight).
Use a small screw driver to poke through this hole and remove the small screw underneath the front sight.
Then remove the front sight, like this...

The Receiver
Now you are left with just the receiver with front and rear sections completely removed.
For the record, your receiver should look like this. My one has been battered quite and lost its cocking handle etc.
Use a thumb to begin prying the plastic receiver shell away from the internal frame, like this:
Carry on raising the receiver shell upwards from the rear end until the pump-lock is
 exposed (small silver metal piece).
Use a pair of pliers to remove the pump-lock and the accompanying spring before it can ping away
 of its own accord (which it almost always does).
Then pull the receiver shell the rest of the way off the internal frame.
At this point the two action bars (long black bits) will be free to fall away from the frame. Go ahead and remove them.
Next, move down towards the trigger guard area and remove the two long thin screws (adjacent to the yellow dots).
Then pull the trigger guard away from the frame.
To further disassemble the trigger guard area - remove this screw which holds on the shot-shell release lever.
Like so...
The push-button safety at the rear of the trigger guard can also be removed (pics pending).
 At the rear of the receiver is the butt-stock attachment stub, remove the two small screws from the end.

This pic illustrates the two stock-attachment-stub screws (blue), the two long thin screws
 which hold on the trigger guard (green) and the small phillips head screw from the top of the receiver frame.

Next move onto the 4 main receiver screws. It is at this point that many disassembly operations fail
 since you need a specific torx T7 driver - something which most guys don't have in their standard tool kits.
 Once you do have one though, removing them couldn't be simpler and that's the last hurdle to jump before
 gaining access to the internals.

Three of these torx screws are at the rear of the receiver frame.

And the last one is at the front near the mag tube attachment.


A pic showing the four main receiver torx screws.

The Internals
At this point the receiver frame can be pryed open - take care when doing so not to lose springs
 and/or damage any components.
With the receiver frame in two halves you will see all the different areas of the internals inside. The loading chamber...
...the trigger group...
...the main spring assembly...
...the shot-shell retention lever...