The basic is field-stripping, where you take the rifle apart well enough to clean it. Cleaning is important. Have you seen the movie Major League? Charlie Sheen (who pitched in college, by the way) is a rocket launcher-armed pitcher who can’t hit the strike zone. He can’t see. He gets glasses, very ugly glasses. The coach remarks “It’s important to see.” One of the other players counters with “It ain’t that important.”
Stripping to clean is that important.
In order to safety-check and to clean or begin armorers work, you must be able to field-strip the AR. Place the safety on “SAFE.” If there is a magazine present, remove it. Pull the charging handle to the rear and lock the bolt open. The bolt hold-open is the lever on the left side of the upper receiver. Keep the charging handle pulled to the rear.
Either pull the wider, serrated paddle part of the bolt hold-open out from the receiver, or press the smaller, lower portion of the bolt hold-open into the receiver body. Ease the bolt forward. Once it stops, you can release pressure on the bolt hold-open. (If you did not pull the charging handle back far enough, the bolt may appear held open, but will snap forward with any slight vibration. Be careful until you have looked at the bolt.)
Press the charging handle forward until it locks in place. Look into the chamber. Use a light if you need to, as an oxidized brass case, or a steel case, may be so dark that you’ll overlook it except in bright light. If your finger fits, reach in and check the chamber. (The ejection port is small, and not many people have fingers small enough to reach. The only method most can use is to reach up from the magazine well.)
With the chamber verified empty, close the bolt. It is best to build correct habits even while doing administrative tasks on the rifle, so close the bolt by pressing or slapping the hold-open lever. The bolt will crash closed. Stop cringing, that is the way it operates when you fire it, so closing the bolt that way is not abuse.
Press the rear takedown pin from the left to the right. Pull it until it stops at its full movement. The upper will hinge away from the lower. (Be careful to control the upper so it doesn’t swing up and strike you in the face.)
Pull the charging handle halfway back. Then grasp the carrier and pull it back, down and out of the rifle. Place it on the table. Pull the charging handle back until it stops, then pull it down and out. Press the front pivot pin from the left to the right until it stops.
The upper and lower receivers can now be separated.
In the field, or in a range class, this is all you need to do to gain access to the working parts for a quick cleaning. From here, aerosol cleaners and lubricant can clean what needs to be cleaned, lubed and reassembled.
But, since you have it apart right now, let’s do a quick inspection and functions check. After all, if you own an AR, or plan to be doing any work on them, these are things you’ll be doing on a regular basis. Best to learn how right away.
An operational checklist is a process whereby you inspect a rifle for proper fit and mechanical function, without firing it. Any fault you covered in an operational check should be corrected before that rifle can be used in a match, practice or for defense. Right now I’m not going to cover the causes and corrections of the faults found, only the process.