Operator Level + Inspections For The M16 FOW

A while back another member asked me to follow up on my previous threads about inspection procedures for the M16/M4 family of weapons. This time the focus was supposed to be on "operator level" tasks. Let me also say this. When doing these inspections you need to have some level of understanding of the weapon and common sense. I cannot account for every scenario that you will encounter.

Now. I'll be the first to admit that the operators manual is a good first step, but not the best resource out there. I am going to attempt to capture that information as well as my own observations over the years. Bear in mind that if you have a Frankengun this information may help, or it may not.

First thing first. Whether you purchase a factory built AR, a custom built AR or something that you have assembled, you need to know what it is that you have.

For example; do you have a carbine, rifle or midlength? Was it put together correctly. Rifle upper/ barrel extension. M4 upper/ barrel extension. Things of that nature. For this post we are going to assume that all is correct.

Step 1. Once you have taken receipt of the weapon or upon completion of the build you should do a thorough inspection beginning at the muzzle and working towards the stock. Ensure that things like screws that should be tight are tight. If something should need Loc-tite, make sure that it does.

Step 2. If you don't see any issues then proceed to field strip the weapon. That means separate the upper and lower receiver, remove the charging handle and bolt carrier group (BCG), remove the firing pin retaining pin, firing pin, bolt cam, extractor pin and extractor. MAKE SURE THAT YOU HAVE THE CORRECT EXTRACTOR SPRING AND INSERT. Remove the buffer and buffer spring.

Step 3. With that done you should be checking the fine details. Look at your stakings on the carrier key. Is the key tight? Do the stakings provide sufficient grab on the screws? Check the key itself and see if the lip around the key is damaged. Look at your firing pin and retaining pin. Is anything bent or otherwise out of order?

This is also a good time to check your gas rings. With a clean BCG insert the bolt and cam pin into the carrier. Stand the carrier up on the bolt face. If the weight of the carrier collapses onto the bolt, then your rings are worn and they need to be replaced. NOTE: Some people have reported that their BCG failed this test and the weapon still runs. That is correct. But, at some point it will be a problem and most likely not when it is the best of times. Gas rings or bolt rings do not need to be staggered. This is an old wives' tale that continues to persist to this day. Ignore it.

You should also check the extractor. Make sure that you have the correct spring and insert. Another thing that I do is test the rim of the extractor lip. I do this by dragging it across my arm. You will normally see little white drag lines and it will feel somewhat sharp. That means you are generally good to go. You want to look at the spring and ensure it's in one piece. NOTE: If you have a rifle you do not need an O-ring. As a matter of fact many carbines do not need an O-ring. In some cases the use of one can result in too much tension on the extractor and it may not grab the rim and extract it. It's a good idea to test it first when you are shooting and make any adjustments.

At this point it is also a good idea to check the ejector spring. The ejector is located in the bolt face on the left side as you look down the weapon. My method is to use a small punch and just push on the ejector. If it feels mushy it should be replaced. I also recommend that you place a few drops of lube on the ejector and work it a few times.

Step 4. Once you have fully inspected the BCG move on to the upper itself. Look for anything out of place within the upper, this includes the handguards and or rail system. Look for cracks in the handguard and that it seats properly into the Delta ring assembly. Check your rail for canting, loose screws, etc... Check the gas tube and make sure it is tight and that the roll pin that secures it to the front sight base (FSB) is in place. This would be a great time to examine the feedramps or lack thereof as well as the FSB to check for any canting. It's also good to see if you have a "F" marked FSB.

Grab the barrel and hold it by the FSB. If you don't have an FSB, hold the end near the flash hider. Grab your upper with the opposite hand and attempt to twist it in opposite directions. If you feel movement (twisting) then there is a high probability your barrel is not seated and torqued properly and it needs to be fixed. You should be able to tell if it is the FSB or barrel moving.

Step 5. Assuming that the upper is good to go and everything is tight and correct, move on to the lower receiver assembly.

At this point you should be starting at the front and working your way back. Make sure that the pivot pin moves freely. Check your magazine and bolt releases. I will usually take a new magazine and insert it into the well and lock it into place and release it several times.

The critical part is now examining the fire control group (FCG). Ensure that everything is installed correctly. Make sure that the legs of the hammer spring are over the trigger pin. This is critical as they hold the trigger pin in place. Unless you disassemble the FCG you will not be able to check the "J" spring within the hammer. The best way to to do so without disassembly is to use a small punch and push against the hammer pin. You should meet resistance and it shouldn't easily move. Make sure that the disconnector moves freely. Cock the hammer and place the weapon on safe. See if the selector lever moves freely. Check the rear take down pin and make sure it is held captive when you pull it out.

Now check the buffer retaining pin. It should move up and down freely and the edge of the lower receiver extension (also known as buffer tube) is sitting on the edge and holds it in place.

At this point you will also want to grasp your buffer tube by the buttstock with one hand and the lower receiver and then attempt to twist in opposite directions. If you feel movement then the tube is not on properly and needs to be checked. Also check that the endplate is installed correctly with the nub facing into the rear of the lower receiver. Make sure that the castle nut is staked in at least two places. This would be a good time to see if you have a commercial or milspec tube. This can be done by looking at the rear of the tube a slanted rear is usually the sign of a commercial tube. You can also measuring the diameter. A commercial tube is 1.17 inches in diameter and milspec is 1.14 inches in diameter. Check your buttstock and see if it moves freely. If you have a rifle stock, then check to make sure that the screw in the rear is in place and tight. It should have a small amount of Loc-tite on it. Check the pistol grip screw and ensure it is tight if you have a hex head type screw, I suggest replacing it with a flat tip Colt screw, unless you have a proprietary grip that needs it.

The final part of the inspection is to measure your action spring (buffer spring) a carbine length spring should measure between 10 1/16 to 11 3/4 in length. A rifle spring should be 11 3/4 to 13 1/2. My rule of thumb for the carbine is I replace it at 10 1/4.
You also will want to check your buffer and determine what you have. A carbine buffer will be plain faced. From there it progresses to H, H2, H3. This is imprinted on the face. A rifle buffer is pretty obvious.

If everything checks out, then reassemble the weapon. NOTE: I find it a good idea to do a basic wipe down and cleaning at this point. I would inspect the barrel for obstructions as well and I would probably punch it a few times.

Step 1. Reassemble the BCG. Insert it into the upper receiver w/o the charging handle and slowly ride it forward. Once you get to the gas tube check for any binding. If it locks up and there is no binding then remove and reinstall with the charging handle.

Step 2. Place the buffer into the buffer spring and reinstall into the lower receiver extension.

Step 3. Place a small amount of lube on the take down pin and pivot pin.

Step 4. Place the upper onto the lower and push the pins in place. At this point you should conduct a basic functions check.

Step 5. Pull the charging handle to the rear to cock the hammer. Place the selector lever on SAFE. Attempt to pull the trigger. It SHOULD NOT fire.

Step 6. Place the selector lever on FIRE and pull the trigger. The weapon SHOULD fire. Continue to hold the trigger to the rear and then cock the weapon again. Slowly release the trigger and listen for the "click". If you don't then there is something wrong and you need to consult with an AR guru.

Step 7. Take an empty magazine and place it into the magazine well. Make sure that it seats and falls freely. Then lock the magazine into place and pull the charging handle to the rear. DO NOT USE THE BOLT LOCK. The follower should pop up, engaging the bolt lock, locking the bolt to the rear. Push the magazine release and drop the magazine. Magazine should fall freely.

That's pretty much it. In order to conduct any other inspections you will need to have the proper gages. Those gages and that process is explained elsewhere.

One more thing. When you go to test fire your weapon it is a very good idea to properly lubricate the weapon. I am not going to get into that process because everyone has their own thoughts on the type of lube and how it should be done. My personal method is to put a very light coat on the bolt and BCG while the weapon is at the house and being stored. Once I head to the range, I apply a fair amount to the BCG again and let it rock. That method has served me well. Additionally. If you use some crap ass ammunition and then wonder why your weapon won't function you probably needn't wonder. I wouldn't use reloads. I would use ammunition that is known to work and has a track record.

If there is something I left out or think I need to address please send me a clear and concise PM and I will make the changes as necessary.