Cpm4 is pretty much of a new map, but already beloved by most for it's original tactics. There are no maps like it. Main difference from the other maps is that there is no Railgun at cpm4. But there are two Rocket Launchers instead. Main things on this map is Red Armor control and good Quad timing. You sould hold the control over the Red Armor and go for Quad in about 25 seconds before it spawns. The main weapon is Rocket Launcher and Lighting Gun. You should time those weapons and never let the enemy get it. If you've got two shafters defending the Red Armor you'll be ok. Rocket Launcher is the best for defending norrow paths, etc. But you got to do a great teamwork. Now let's speak about RA defence positions:
One with RL should cover the path from the lower Shotgun near the portal. Another covers the higher Shotgun, and the rest of team take RL, LG and RA.
One of the teammates (desireble the one with a lot of armour) goes for Quad in 20-25 seconds before it spawns. Try to use the pass behind the Red Armor.
When the first one gets to the path opposite to the teleport he should tell it to the one who covers lower Shotgun pass and he should jump to a Quad teleport.
At the same time the one who covers higher Shotgun moves to a Quad area as well.
The last team member is left to defend the Red Armor. The most effective thing to do is to cover an armour bridge.
You can as well help yor teammates if they've got problems at Quad. All you have to do is simply jump of the Red Armor and run to the Quad area through the closest pass.
If you succeed and got the Quad one of the players should fall back to the Red Armor area and the Quader goes to the Plasma Gun and only then goes back to RA. And One of the players should try to take the control over the higher Rocket Launcher. If he'll do it you'll have the total control over the map.
If the tactics above was used against you try to drop down the game speed, hide and don't let them frag you. Concentrate on the next Quad. Well, of course, if the enemy is so impudent to run all over the map there is no point in hiding. Instead of it try to attack the Red Armor. Two of you should attack from the jump pad, third one from the higher Shotgun and the last one will cover the second floor. But never attack if the enemy plays defendevly. Try to hold the passes to the armour, that'll make a kind of frontline with Red Armor on one side and Quad Damage on another. Now let's speak about the in-game points.
One covers Quad and higher Shotgun path.
Another covers Plasma Gun and lower Shotgun path. Together they will try to force enemy to fall back.
The rest of the team should pay attention to a Quad portal. One of them simply stand behind the teleport with the Rocket Launcher and another should wait for Quad Damage. If someone gets killed he should tell it immediately and those who still alive should look to the empty path. If you've got Quad next thing to do is to attack the Red Armor. Attack from the higher and lower Shotguns and the second floor at once. Try to rocket jump to get RA.
Quader attacks last. The best way to do is to use a pass from Lighting Gun.
When you took over the RA control don't miss the next Quad and frag 'em all.
One with RL should cover the path from the lower Shotgun near the portal. Another covers the higher Shotgun, and the rest of team take RL, LG and RA.
One of the teammates (desireble the one with a lot of armour) goes for Quad in 20-25 seconds before it spawns. Try to use the pass behind the Red Armor.
When the first one gets to the path opposite to the teleport he should tell it to the one who covers lower Shotgun pass and he should jump to a Quad teleport.
At the same time the one who covers higher Shotgun moves to a Quad area as well.
The last team member is left to defend the Red Armor. The most effective thing to do is to cover an armour bridge.
You can as well help yor teammates if they've got problems at Quad. All you have to do is simply jump of the Red Armor and run to the Quad area through the closest pass. 
If you succeed and got the Quad one of the players should fall back to the Red Armor area and the Quader goes to the Plasma Gun and only then goes back to RA. And One of the players should try to take the control over the higher Rocket Launcher. If he'll do it you'll have the total control over the map.
Quader attacks last. The best way to do is to use a pass from Lighting Gun.
