Field Stripping can be done with what everyone should have out in the field, a bullet. Might not be the best tool, but in a pinch it will do everything you need to do. First thing you need to do is to remove the magazine, clear the weapon, ensure the bolt carrier group is forward and the safety is on. Set the firearm so the barrel is pointer to the right. Push the rear take down pin towards you, it will not come all the way out and you should feel the upper and lower separate when it is pushed far enough. Now do the same for the front take down pin. You can now separate the upper from the lower receiver.
To disassemble the upper receiver pull the charging handle back and remove the bolt carrier group. The charging handle will drop down as you continue to pull and can be removed from the receiver. On the left rear side of the bolt carrier, you’ll see what looks like a cotter pin, this is the firing-pin retaining pin. Pull the pin straight out and the firing pin will drop out of the bolt. Turn and remove the cam pin the bolt will now slide out. Make sure the gas ring gaps are not lined up and are in good shape. Next remove the extractor pin, the extractor will then come out. Inspect the extractor assembly spring and rubber piece to ensure good working order. Clean everything up with a small cleaning brush and solvent then wipe down with CLP. Re-assemble the bolt by putting the extractor and spring assembly back in the bolt and inserting the extractor pin, return the bolt to the carrier and insert the cam pin and rotate, insert the firing pin and the retaining pin. Run a couple swabs with solvent followed by CLP down the barrel. Insert the bolt group and charging handle to the upper receiver.
The lower assemble contains the trigger group, buffer system and the stock. To remove the buffer and spring, push in on the buffer and depress the retainer pin. The buffer and spring will come out. Clean the buffer assembly, spring, and tube with a swab dampened with CLP. The trigger assembly will require some grease at the pivot points. Inspect the stock for cracks and other damage.
The AR-15-style firearm is a versatile, modular, and easy to maintain rifle that with a little maintenance will last you a very long time.
U.S. Army TM 9-1005-319-10