Unscrew the end cap on the stock fore-end. slide out the barrel. slide off the fore arm. punch out the two pins holding the trigger assembly. slide out the trigger assembly. remove the charging handle by pulling out as it is only held by a detent spring and ball. push in on the end of the tube opposite the stock end until the detent on the rails matches up to the small cutout on the tube. pull up on the rail and that releases the gas tube assembly and spring. press in on the spring plate that the bolt assembly runs into as your sliding it out of the receiver and the bolt and rail assembly will slide out. clean and reassemble. No lube in the gas tube area.
Take it to a gunsmith
The actual magazine tube that connects to the receiver is brazed in there, so it removing it isn't an optimum solution.
Unscrew the magazine tube cap, pull the barrel off to the front, remove the forestock. If in doubt, consult the owner's manual. A replacement owners manual is available through Remington's web page.
You can request a manual from Remington on their web site.
If you mean the magazine, there is a magazine release button on the left side of the gun. You press the button and the magazine comes out.
With the bolt open and locked, remove the magazine nut and slide the barrel and forend off the shotgun. Replace the nut on the magazine tube (you'll see why in a minute). If you look towards the end of the magazine tube (toward muzzle), you will see a round notch in it. Gently let the bolt move forward until the peg in the slide aligns with the round notch, and lift up carefully. When the slide releases from the piston, the piston will slide forward until it hits the magazine nut. You may now remove the magazine nut and slide the piston and magazine spring from the shotgun. Replace the piston and reassemble in reverse sequence.
Best left to a gunsmith
There is a small level protruding from the bottom at the side of the magazine. Push that level back (or forward, I forget which) and the magazine comes straght out the bottom.
Remove the cap from the end of the tube and be careful of the spring which is under pressure. The plug will come out with the cap.
Best left to a trained gunsmith
remove the magazine cap by unscrewing, then the forearm will slip off. then pull the barrel off.
If you are referring to the magazine tube plug. The answer would be No. It is put there for bird hunting regulations only.