Photo courtesy Armalite
This photo shows properly staked gas-key cap screws holding the gas key onto the bolt carrier. Photos Jeff Chudwin
This photo shows the crushed metal staking around the cam pinhole that prevents the cam pin from being inserted the wrong direction.Photos Jeff Chudwin
This bolt broke around the cam pinhole.Photos Jeff Chudwin
Here the retaining pin is correctly located behind the firing-pin flange.Photos Jeff Chudwin
And here the retaining pin is incorrectly located in front of the firing-pin flange. Note: the parts are shown outside of the bolt carrier for illustration purposes. Photos Jeff Chudwin
FEATURED IN TACTICS AND WEAPONS
The patrol rifle has become a standard piece of equipment in many police agencies nationwide, and the AR-15/M-16 type rifle is the dominant weapon system. In use since the 1960s, the AR system has received much praise, but also significant complaint.
To obtain reliable, consistent function with one of these weapons, you must maintain it. The following suggestions are based on the decades of combined experience our training cadre has working with this weapon system in training courses, in competition and on the street. Certainly not all-inclusive, these suggestions provide simple and inexpensive solutions to problems that have, at times, plagued officers using these firearms.
Failure to Cycle
Check for a loose gas key on the bolt carrier. (This is the round tubular piece located on top of the bolt carrier.) Recently I ve seen far too many rifles come from factories with loose keys that cause the weapon to short cycle. We ve had a number of AR-type carbines fail to function due to the gas key on the bolt carrier coming loose. When this occurs, the bolt carrier does not get sufficient gas into it to move fully to the rear to extract, eject, cock and feed a live round. You will see an empty case jammed at the top of the feedway with a live round partially fed underneath. When I say fed, I mean the bolt lugs have dug into the live cartridge at the top of the magazine and dragged it forward toward the feed ramp. The bolt is on top of the round, not feeding from the rear.
A simple check: Every time you field-strip your weapon, simply grasp the bolt carrier and twist the carrier key by hand. If loose, it will move, and any movement indicates the gas seal is broken. The repair is simple (have a trained armorer do this): Unscrew the carrier key by removing the two cap screws. After removing the bolt assembly, clean all surfaces with a non-petroleum based degreaser, apply Locktight 640-green color to sleeve and bearing (or red color 272), and reassemble. Tighten down hand-tight with an Allen wrench and let cure overnight for best results. You can then restake the area above the cap screws. In classes, we ve put them back on the line after an hour and it worked fine.
Michiguns Ltd. (www.m-guns.com/tool.php) has developed a new tool designed to take the effort out of staking AR gas keys called MOACKS. I highly recommend this multipurpose tool to all armorers and serious AR users.
Make sure the three stainless-steel gas rings located on the bolt are unbroken and unbent. Some claim all three gas-ring gaps must be in line to prevent gas blow-through and short cycling. In practice, however, I ve never seen this occur.
Other than wear, most damage to gas rings occurs due to improper cleaning. Using stainless-steel brushes around the gas-ring area can bend or tear out gas rings. One SWAT officer came to a nearby department s weapon inspection with only one gas ring attached to the bolt. This was a sure failure on his part to know and understand his weapon, but also a disaster in waiting. Had he deployed the rifle, it would have fired once and then failed to operate.
Check gas rings for wear by removing the bolt carrier group from the rifle and standing the bolt on its face with the carrier vertically above it. If the weight of the bolt carrier causes the bolt to collapse inward, replace the gas rings. Replace all three at the same time. Gas rings cost very little; buy several extra sets and keep them in your roll-out gear bag.
Again, do not use a metal cleaning brush on or near the gas rings it can bend or remove them.
Failure to Extract/Eject
Make sure the extractor spring is locked in the extractor spring seat, with the newest series black-colored elastomer bushing in place inside the extractor spring. I highly recommend the addition of MGI Inc. s D-Fender. This small horseshoe-shaped polymer piece goes over the extractor spring and adds four times more extractor tension. Good for many thousands of rounds, the D-Fender has all but eliminated our extraction-ejection failures, which were far too common in the AR-15/M-16 system. Of all the after-market parts, I consider this the most significant. None of our rifles goes out on the street without a D-Fender. We have yet to wear one out.
Make sure the ejector has a forward beveled edge. If not, remove and bevel it, or replace it. A sharp edge on the ejector cuts brass from the base of the cartridge case as the bolt turns into and out of lock up. These brass shavings move into the ejector tunnel and can cause the ejector to freeze into a compressed position. The weapon cannot eject and fails to operate.
Check the extractor for brass and fouling build-up under the extractor lip. The extractor on the AR system is small and the lip shallow. Keep it clean and inspect for any damage.
Make sure the bolt-cam pinhole is staked (crushed metal) on the extractor side to prevent inserting the bolt into the bolt carrier 180-degrees opposite the correct reassembly, which would cause the weapon to attempt to eject out the left side of the upper receiver where there is no ejection port.
Bolts can crack and break in two pieces. Check for cracking around the cam pinhole. Some producers recommend replacing bolts after 7,000 10,000 rounds. We have competition guns built in the 1970s that have many tens of thousands of rounds fired and have never experienced a broken bolt. Still, if your life depends on a working rifle, replace the bolt as recommended.
Check the barrel-to-upper-receiver fit. Make sure it s not loose. We have seen a number of new weapons from the factory come with barrels not properly screwed down. A loose barrel allows the front sight to move side-to-side relative to the rear sight very bad for accuracy.
Check for barrel center. The rear sight should be centered after sight in, or close to center. Weapons have come from the factory with the front-sight assembly off center. These rifles could not be sighted in.
For pre sight-in, check that the base of the front sight is even in height with the sight base tunnel, and that on the A-2/3 rear-sight with the drum elevation the sight assembly is bottomed out at the 3/8 or 3/6 markings. Adjust according to your sight-in procedure. Failure to check this setting has caused significant delay in classes when officers, not knowing about this issue, attempt to sight in a rifle with the elevation set far out of adjustment.
Reassembly After Cleaning
Critical: On reassembly, make sure the firing-pin retaining pin is reassembled behind the firing-pin flange. If an officer mistakenly places the firing-pin retaining pin in front of the firing pin, the firing pin will be locked in place, rendering the weapon useless. To check this, turn the bolt-carrier assembly on end and slap the unit into your palm. If the firing pin retaining pin is properly positioned, the firing pin will hold in place; if not, the firing pin will fall out into your palm.
Too often an officer or agency purchases a rifle and tests it on the range with a magazine or two of ammunition. But as I ve seen numerous times, a true test of the weapon prior to putting it out on the street where lives depend on proper function requires hundreds of rounds. From live-fire use comes proof of reliability, not assumption.
Students taking our basic patrol-rifle class fire a minimum of 750 rounds, and every AR-15 rifle/carbine manufacturer represented in our classes has had issues with parts and function at some time.
This review of parts and maintenance can prevent catastrophic failure of the AR-15/M-16 weapon system. Failure on the range is an inconvenience. Failure on the street can mean the difference between life and death. The adage know your gear, protect your life remains the bottom line.