AR-15 Maintenance and Repair- Five Tips from Armorer’s School

Written by Greg Ellifritz

Topics: Articles

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Written by Greg Ellifritz



Last week I attended Colt’s AR-15/M-16/M-4 Armorer’s school.  It wasn’t the first time I’ve been through it.  The certification is only good for three years and needs to be periodically updated in order to purchase Colt weapons parts direct from the factory.



I had previously attended the same class and also have a different company’s AR-15 armorer’s certification.  I have to admit that nothing has really changed in the design of either the course or the rifle, but it is still good to review some of the basics.



I wrote down a few bits of information that I had either forgotten from past classes or had never heard.  I think they may be of interest to anyone who shoots an AR-15 or has the opportunity to work on one.  Read up if you fit that description.  These tips may save you some time, money and hassle:



1) Almost all functioning problems in the AR-15 rifle can be traced back to poor lubrication, bad magazines, or a bad extractor spring assembly.  The instructor commented that whenever he gets a rifle that is malfunctioning, he immediately replaces the extractor spring assembly.  For those unfamiliar with the term, the extractor spring assembly is in the bolt and is located under the extractor.  The assembly consists of a spring and a plastic post that is inserted in the center of the spring.



These parts wear out over time and need to be replaced regularly.  Colt has no set replacement schedule in terms of round count, but the instructor noted that he would replace them annually in a gun that is fired extensively.  The most current extractor springs from Colt have a copper colored-wash on them.  They’re cheap.  Get a few and swap them out in your older weapons.  I get mine from Brownells.


Colt extractor spring assembly (courtesy of



2) Another very common problem with AR-15 rifles is that the bolt carrier key loosens and causes gas to leak from the system.  I’ve personally seen this happen quite a bit in my classes.  It seems to happen more on Bushmaster and DPMS guns than any other brand.  With that said, I’ve even seen some high dollar guns (like a Wilson Combat) with loose or improperly staked carrier keys.


The carrier key is the detached part. If the screws are loosened or become unstaked, you will likely see failures to extract. The carrier key should be tight and should not have any play or movement.


I see the problem so often, that I bought a staking tool to re-stake the carrier key screws to prevent loosening.  If you don’t have the skills to hand stake the screws and don’t want to purchase the machine, the instructor suggested using loctite as an alternative.  Run a thin bead of red LocTite all around the underside of the carrier key before tightening the screws.  The instructor stated that his results doing that were just as good as he had seen restaking the screws.



I still think I’ll use my staking tool, but it’s a good fact to know if I am ever in a situation where I don’t have my tools.



3) Colt rifles are more expensive than most production quality AR-15s.  One of the reasons is that Colt does more magnetic particle testing on its component parts.  A common trick when selling used guns is to swap out an original Colt bolt carrier group with a lower budget alternative.  Colt marks all of its bolts and bolt carriers with the letter “C”, or the letters “CMP”.  If your bolt doesn’t have those letters stamped into it, you aren’t buying a Colt.



4) People are getting better about putting adequate lubrication on the bolt.  Inadequate lubrication is the cause of many AR-15 rifle malfunctions.  The instructor noted that the pendulum may have swung too far, with shooters applying TOO MUCH oil to the bolt.  If too much oil is applied, it can fill the firing pin hole, reducing the striking power of the firing pin.  If you are getting light strikes on your priimers, make sure you aren’t over lubricating.



5) People often talk about “Sub-MOA” (shooting less than 1″ groups at 100 yards) AR-15 rifles.  I’ve seen some rifles and shooters capable of such accuracy, but it isn’t nearly as common as the gun forums might lead you to believe.  Do you know what the military standard is for accuracy testing in the M-4?



You might be surprised to find that the military specifications require a 10-shot group fired from a rest at 100 yards to be under FIVE inches!  Colt rifles average two and a half to three inches.  Don’t feel bad if those sub-MOA groups have been eluding you.  Your rifle may not be capable of that level of accuracy!



It pays to have a basic understanding of how your rifle works.  I’d encourage everyone who owns an AR-15 to take some type of armorer’s course.  It’s a skill that is definitely worth acquiring.



If you have any AR-15 specific questions, post them in the comments below and I’ll answer them if I can.




12 Comments For This Post I'd Love to Hear Yours!

  1. john says:

    Curious as to what your thoughts are on the rubber rings that are coming on some of the rifles now a days. When i bought my first daniel defense the extractor spring did not come with this, my newer one did. I have had no different between either rifle through TDI rifle 1 and Tactical response fighting rifle. Both are still using their original springs and equipment.

    • Greg Ellifritz says:

      I use them in all of my rifles and have found them to greatly reduce malfunctions. I asked the armorer instructor about them and he said that Colt placed them around the springs for awhile, but didn’t find any significant benefit. Colt discontinued the practice of using them and now just advocates regularly replacing the extractor spring.

      I will continue to run them in my rifles.

  2. John J says:

    The rubber O-rings really shine when you are shooting steel case ammo vs. brass. Just remember that the O-ring is subjected to same high heat and should be replaced right along with your spring and insert.

    What ammo are you using to try to shoot MOA? M855 isn’t known for it’s accuracy and the military accepts lots that will shoot 2+ MOA. Try some precision ammo with a bullet weight for your twist rate and you may be surprised.

    I recently removed my optic, rails, and replaced my barrel. Re-assembled the rifle using the specified torque and only had to move the POA 2 clicks up and one click right on an Aimpoint H-1. Buy quality gear and you won’t have impact shifts just beacuse you cleaned your gun!

    Even new quality GI Mag with MAGPUL followers aren’t as reliable as the new generation of polymer mags!

    SLIP 2000 EWL is my favorite lube, and I may be guilty of overusing the stuff!

    Thanks Greg!

  3. Dann in Ohio says:

    I seem to be having good results lately with Frog Lube… any thoughts on a preferred lubricant for the AR?

    Dann in Ohio

  4. Marty says:

    Greg, Thank You for the great articles. I point a lot of ppl to them to help answer their questions. I have been using a silicone based lube such as Remington dry lube onon my CCW piece with good results, I even did a 800 round Combat Focus Shooting course. It seems to collect less residue then Rem-oil. Have you done any research on this type of lube? If so, Do you feel this is ok for Semi-auto pistols? Ar rifles? Thanks again Marty.

    • Greg Ellifritz says:

      I don’t have any significant experience with that kind of lubrication. There’s a lot of stuff out there that works well. If your gun stays running, I’d say it’s just fine!

  5. Bob Aydelotte says:


    When I charge my AR-15 bolt my buffer retainer pin and spring come out.

    It happened right after I purchased it new at a gun show last year. Re-assembled it and it worked great for about 10 rounds. Then replaced buffer retainer spring due to damage. And, it comes out as soon as I charge bolt.

    Any ideas?

    • Greg Ellifritz says:

      That pin and spring are held in place by the buffer tube itself. When you replace the pin, compress it as you screw in the buffer tube. Keep screwing in the tube until it reaches the vertical extension on the pin. The pin will stay in place.

  6. Elie Spinks says:

    I have an ASA ar15, and when a live round is in the chamber,I cannot eject it manually without using a screwdriver to force the bolt open. The gun is kept clean and well oiled.

  7. Don Stanton says:

    I have noticed on one of my AR 15’s the handguard cap is loose. This leads to shifting in the guards when pressure is applied. Is there a way to correct this? The AR in question has a pinned FSB and it is my understanding that the only thing that keeps the cap in place is pressure between the rear of the FSB and the barrel shoulder behind the cap. I am of the opinion that the only way to correct this is to unpin the FSB and install a new cap. The cap in question is the round carbine type. How do the manufacturers do it? Your assistance is appreciated.

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