National AR-15 Bolt Maintenance Day!

One of the more critical bits of information to percolate out from the massively parallel carbine training efforts in this country is that the bolt in the Stoner pattern rifle has a limited lifespan.  Typically, the failure mode is to crack around the cam pin hole.  The rifle will continue to operate with a cracked bolt, until the bolt fractures completely in two.  Bolts seem to last around 35k rounds in a semi-only 20″ gun, about 20k rounds in a semi-only 16″ gun, to as little as 10k rounds in a 14.5″ M4 that sees a lot of full-auto fire.

If you own an AR, regularly shoot it, and consider it a ‘go-to’ gun in your self-defense battery, I’d like you to take fifteen minutes out of your day today and check your bolt for cracks.  Check to see that your rifle is empty, then go ahead and check it again.  Push out the rear takedown pin and remove the bolt carrier group.  Since you cleaned it right after the last time you shot it (right? Right?), you should be able to easily check it.  Under a bright light, visually check the circumference of the bolt around the cam pin hole, then feel with your thumbnail by dragging it fore and aft down the bolt surface.  Don’t forget to look in the cam pin hole too.  If you have a can of starter fluid or some rubbing alcohol handy, spray that on the bolt.  It will quickly evaporate from the surface, but linger in any cracks.

Go ahead and also check your spare bolt for cracks.  What, you don’t have a spare bolt?  What else do you think goes in the hollow of the pistol grip? Tsk tsk!

While we’re at it, push out the extractor pin and check your extractor spring to make sure it’s not broken, and it has the correct black rubber nub insert installed.  If you run a SBR or even a 16″ gun with an M4 length gas tube, a D-Fender d-ring is a cheap piece of insurance.

Now would also be a good time to check your screws holding the gas key on the bolt carrier.  These should be staked, but many AR factories do not, or do a poor job.  You will need an Allen wrench.  If your screws are not staked, find someone with a MOACKS and slip them a tenner to turn the screws for you.  Brownells now sells a cheaper version that only runs $70.  Don’t bother with locktite on these screws, and for Stoner’s sake, don’t let anyone bang on your carrier with a cold chisel.

If everything checks out, reapply your lube of choice and reassemble your black blaster!  Don’t you feel better?  I know I do!  Please remember to add this little chore to your regular post-practice cleanup and you’ll be very smug indeed when the zombies attack.


  1. AK bolts break too. Also, that stupid stranded spring wire can get trapped under things where it’s not supposed to be and fark things up.

    Guns break, all of them. You gotta learn to deal.

  2. While you have the bolt out, check the lugs for cracks as well. As far as failures go, sheared lugs are right up there on the list.

  3. A timely reminder to check my AR when I get home. Thanks.
    Of course I’ll look at the ’03 Springfield and wonder how much ’06 ammo I could get for my AR.

  4. FALs and AKs and HKs don’t break or malf on the internets because on the internets people are talking instead of shooting.

    FALs and AKs and HKs that get shot a lot at gun skule break a lot just like every other gun at gun skule.

    If you actually use your rifle, you will eventually wear it out. Paw-paw’s Winchester lasted forever because it only shot twenty or a hundred rounds a year, usually right before deer season.

  5. I originally posted that as a joke… Kinda like in the “caliber wars” post a month back.

    It takes a lot to wear any rifle out. and all designs have pros and cons…

    God bless America! We’ve got the freedom to own more than one in almost any system we choose!

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