About 6 percent of the Army’s rifles and carbines are going bang when they shouldn’t, but the fix is easy. (Photo: Patrick A. Albright/Army)
The U.S. Army recently tested a sample of 50,000 rifles and carbines and found that they have a problem. A small but significant percentage of these rifles fire, under the right condition, when put on “semi” or “auto” fire, without pulling the trigger.
The problem happens if the safety is placed between the two modes of fire and the trigger is pulled. The rifles won’t discharge then, but they will when the safety is switched over.
The Tank-automotive and Armaments Command, or TACOM, found the problem earlier this year when they reported that 3,000 of the 50,000 tested rifles failed in testing.
“After receiving a significant number of reports from the field and an average failure rate of about 6 percent of the weapons inspected, we ended the inspections and have determined that the cause of the problem is a tolerance stack of the internal firing components,” said TACOM’s R. Slade Walters to Military.com.
“The problem is fixed by modifying the selector to remove the tolerance issue and the fault,” said Walters. “TACOM is working on an Army-wide directive to repair weapons with the issue that will be released when it is approved at the appropriate levels.”
“Each individual part conforms to the tolerance requirements, but when the multiple parts get stuck together in 6 to 9 percent of the weapons,” explained Walters, “those tolerances create that condition.”
Fortunately the fix is pretty easy. The problem only happens with oversize fire control parts, so armorers can re-shape existing parts without having to replace them entirely.
“When they do that, it fixes the problem,” he said. “When they have done it and repeated it, they have been able to correct the problem in weapons showing the issue.”
While the carbines failed inspections at 6 percent on average, the M4A1 stood out as the most commonly affected. Interestingly, none of the M16A4s failed during testing.
Specifically, converted Product Improvement Plan, or M4A1 PIP carbines suffered the most, with a 9 percent failure rate, or 2,070 failures out of 23,000 tested. Original M4A1 carbines failed at the average rate of 6 percent, while 1 percent of M16A2s showed problems in testing.
See Also: Ruger Precision Rifle Recall – Uncommon but Crucial
The Marine Corps also issues M4 carbines and is aware of the potential problem, although the Marines have not published details about failure rates, only that they are addressing it.
The Army will be conducting dry-fire drills and have soldiers test their rifles to see if they exhibit failures. The drill is simple. First cock the rifle or carbine, put the bolt into battery, put the selector on safe and pull the trigger. If the hammer drops, it needs work.
Repeat it with the selector in the halfway position between semi and auto or burst and pull the trigger. Then move the selector into either fire position and if the hammer drops, it needs work. Otherwise it passes the test.
Given the potential risk associated with this type of problem, the Army is moving fast to address the issue.
The first rule of gun safety is to ALWAYS keep it pointed in a safe direction, loaded, empty no matter what. In 35 years of being a gunsmith I have had accidental discharges but never an accident resulting from one because of rule number one. No armorer or gunsmith I know lets a gun out of their hands until it passes the safety test, this should have been caught early. As always, I do hope no one got hurt finding out.
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Which is why the first rule of gun safety is so important. ALWAYS TREAT EVERY GUN AS BEING LOADED! Any time a cartridge is loaded, anything touched or moved, a cartridge is ejected, a broken extractor, etc, or a gun dropped–IT MAY FIRE! There are no guarantees everything will work properly.
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And some troops are too stupid to ever be trusted with a loaded gun. During my 1964 Army Basic Training after completing the rifle range shooting–the Sergeant ordered us to clear the rifles. Remove the magazine, pull the bolt back, and inspect the chamber / magazine well to make sure there was no round still in the rifle. And then to point it downrange, pull the trigger, and push the M-14 safety to the rear.
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Occasionally–BOOM! And one time during the march back to the barracks–BOOM!! When the rifles were supposed to be empty, the safeties on, and the rifles on the slings on our shoulders. Fortunately–the bullet didn’t hit anybody or anything important.
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Not to mention the USEFUL IDIOT! mistakes on the Grenade Range and during the total darkness WW1 style No Man’s Land mud / barbwire / CS gas / simulated artillery explosion crawl under live machine fire!
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John Bibb
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Wow, they are just finding this out now ? When i was in the US Army in the early 1980s, 2 of us got kicked off a range for this exact problem ! I told the armorer what the issue was and he told me that i was full of crap, then, I showed the armorer by making it happen without live ammo! It is a wear issue on the mating surface between the hammer and trigger. It took them 34 years to figure out what i knew in 1984 ? WOW
Just as a matter of enlightened self interest, has anyone done any testing to determine if this problem exists to any degree with, or has any application to, the operation of semi-automatic, non-select fire, AR-15s, say, for example, if the safety is left anywhere between Fire and Safe?
I think teaching trigger discipline would go a long way to eliminating this in the future. To be pulling the trigger while operating the safety seems like a really bad habit and a good way to wear parts prematurely.
GM allowed deviations of productions specs that by themselves were not an issue but combined with approved deviations in the mating parts allowed the two halves of power brake boosters to separate leaving the auto with no brakes whatsoever. No one envisioned that could ever happen. Big production runs with everything go, go, go, is when this stuff happens. Find them. Fix them. Go on.
You don’t mention who made these rifles. Just wondering.
When you put any device in the hands of a teenager they will find every flaw no mater how improbable.
Can’t just blame teenagers. I’ve seen many “adults” create unsafe situations with supposedly idiot-proof devices and procedures. Ultimately, one must realize NOTHING can be made idiot-proof; idiots are just too ingenious. Or, as Einstein noted, “The difference between stupidity and genius is that genius has its limits.”
I can’t believe somebody asked how a soldier figured out the weapon would discharge if placed between fire and safe or full and semi ( whatever it is now !) That’s a soldiers job – know that weapon inside and out – that’s his life and the life of his teammates depending on that weapon.
Dr Motown,
Try re-reading the article.
The part is not defective.
This is a case of ‘tolerance-stacking.
You can use Google as a research tool to figure out what that means.
You don’t know that. When trigger, hammer,safety parts get sloppy. It could be under diameter safety bar or flat.
(defective) It could be safety or hammer, trigger pin hole location. Or over diameter holes. If Multiple parts are too loose to work
Something is out of spec (defective) Or unserviceable
it is tolerance stacking as stated in the article. The parts are not undersize, they are at max dimension. As the article explained, this can be corrected in the field by fitting the parts, e.g. reducing their size. The failure and fix was described in the article.
As described in the article, it is a tolerance stackup problem, AKA an engineering problem. It is the engineer’s job to verify that tolerance stacking does not result in malfunctions.
Cant they just point the rifle at a socialist while testing it fully loaded ?
Just one?
Why would any body put the selector switch in between positions and pull the trigger? How do you even come to discover something like this, when you should not be doing it? Strange.
Will the ATF be filing charges for the failures? Tolerance stacking can potentially cause unintended full or burst fire in many guns. I only ask because there are documented cases of people having been convicted of “possession of a machine gun” when it was just worn parts.
Pretty high rate of failure! Are the defective parts coming from one supplier?