Step 1: Clear your weapon and make sure it is unloaded before starting disassembly.
Step 2: Press out the rear takedown pin, located behind and to the right of the selector switch Press it out from left to the right. It is captivated, do not use force to pull it out, it is supposed to stay in the lower reciever
Step 3: Separate the upper from the lower by pressing the front pivot pin out from the left to right. It is captivated, do not use force to pull it out, it is supposed to stay in the lower reciever
On the rear takedown pin and front pivot pin, follow dwillHK's advice on depressing the buttons inside the pins.
Step 4: Pull charging handle to the rear and remove bolt. Align charging handle with cut-outs in the upper reciever and remove.
Step 5: Remove hand guard by loosening the two locking screws located on the right side. They are captivated in the hand guard, and not supposed to come out. When the screws are loose, pull out until they stop, then slide hand guard off towards the muzzle.
Step 6: Pull op-rod to the rear until it disconnects from piston, and pull towards muzzle to remove from upper reciever. Remove piston by pulling it towards the rear.
Step 7: Depress the buffer retaining pin, and pull out the buffer and action spring
Step 8: Disassembly of bolt carrier group. Pull out the firing pin retaining pin, from right to left. If captivated, leave it in the bolt carrier. Push up on firing pin safety, and remove firing pin and firing pin spring. Lift the cam pin out and remove the bolt.
To assemble, do it reverse order. Only thing to look out for is that you have to lift the firing pin safety up, press the firing pin and spring all the way in before you can lock the firing pin retaining pin in place.
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This is as far as I would take it to begin with. Before going to the range, make sure every part is properly lubed, except the inside of the barrel. Not dripping wet, but a nice coating of a good lube (I personally use CLP on all my guns, but it seems that product is shunned in the US)
If any of the part names are unclear, let me know and I'll post some pictures with references.