I have had possession of a relatively new (I'm 2nd owner) AR15 S&W and just had something occur the other day that is really rather disconcerting. After chambering a round (55 grain SP) I aimed the weapon downrange, and when nearly ready to fire, placed the safety from off, to 'fire." Without getting NEAR the trigger, the weapon discharged the round I had just chambered.
*** , eh? What causes this and how might I best fix THIS little problem that has caused me to shelf the darned thing until fixed...

Was the fire control group modified? If so and you are handy, replace with factory or mil-spec components. If not, contact S&W customer service or seek help from local professional gunsmith.

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Good call. You never know what a previous owner monkey'ed with! Check out this 3D animation. This should give you some idea on the operation of the trigger group.

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SIC SEMPER TYRANNIS

The ability of Bubba to screw up a perfect AR-15 is nearly unlimited. A PSD contractor in Baghdad last year had an AD in the Embassy Chancery lobby - too much diddling with the mechanism.

Did you try and recreate what happened the first time? Chamber a round and take the safety off to see if it would fire again? I believe I would call S&W and see what they have to say?

That sucks. Probably been messed with by an idiot. Should be an easy fix; new hammer and sear will probably do it. I bought an old Cobray M11/9 (semi clone of an ingram mac11) a while back, and the first time i let the charging handle go, it dumped 28 rounds full auto, no way to stop it. Some jackwagon had lengthened the firing pin tip by welding.

Is this the first time you've fired the rifle since you got it?

Once it unintentionally discharged, did it eject the fired cartridge, load another and go into battery again? (properly cycled?)

Did you try to fire the rifle again by pulling the trigger?


My guess would be, if the previous owner has messed with it, he honed the sear on the hammer, attempting to smooth the pull and decrease trigger travel. There's not enough "shelf" left on the sear to safely hold the hammer back, and all it takes is a tad of movement within the trigger group when the safety is released for the sear to break. Best bet is to install a completely new trigger and safety assembly.

Look at it as an opportunity to get a nice performance trigger group, that has been properly designed and tuned. Might cost you a few bucks, but will make your AR better. If all you plan to do is plink, stay with a single stage, but if you want to get serious with target shooting, go for a nice 2-stage. Geissele would be my choice. (and it was, when I built my AR)

I agree with Hair Trigger get a nice upgrade drop in trigger and you should be good to go.

Unless you are knowledgeable about such things you should contact S&W or a gunsmith. The fact that you posted this leads me to believe you should contact an expert.

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Foster Positivity.

As much as I truly appreciate all the great response to this particular issue I face with this firearm, I should have mentioned right up front that I KNOW the guy I bought this from. I bought it from him because of a bunch of social conditions, some of them involved marriage to a woman who doesn't like "black guns." To say the least, I know he knows NOTHING of modifying firearms and he had just purchased the gun with three boxes of Rem Ammo, got a 5 and 10 round mag with it and put a cheesy little .22 3X9 scope on it. I agreed to remove the scope for him so he could have it, but he fired 4 rounds through it before I got it. He purchased it brand spanking new here, in Idaho. I know this, because I have the receipt. When I inspected the weapon before purchase I noticed a slight bit of carbon leftovers from GSR in the chamber, bolt group, etc. It almost looked like what you would expect from those that test the weapon at the manufacturer, not the shooter. Certainly didn't explain WHY the round goes off when no finger on the trigger and the safety is moved to "fire". I have tried it twice. Both times resulted in detonation without trigger on finger. I believe it came from the factory like this, because the friend who sold it to me never even USED the safety, he just put a mag in it and fired it four times. So...my question to all you very experienced and good people out there, is has this happened before? I WILL consult Smith first thing tomorrow morning, but it would be interesting if I wasn't the only one this happened to. Thanks again for all your very giving and honest opinions and experiences.
Dave

OOPS!

Do you really recommend replicating an ND/defective firearm with a loaded chamber?

Asking for a friend.

Function/safety checking a firearm is done with an empty firearm first before attempting a live fire test! Any defects are repaired before loading.

Smiles,

S&W has excellent quality control from personal experience so I would be shocked if this M&P15 left the factory with this safety flaw. So still suspect somebody mucked with it after it left factory.

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Are you referring to a AR15 rifle in like 223 cal or a MP15 in .22 ?

If it is a MP15-22 then refer to :
M&P15-22 Consumer Safety Alert | Smith & Wesson

He chambered a 55 gr soft point.

I'd call Smith & Wesson customer service and let them deal with it. Shouldn't cost you anything, but you might want to ask your buddy if he registered the purchase with S&W. They usually aren't picky about the warranty if it involves a safety issue.

Just because someone "knows nothing about modifying firearms" doesn't prevent them from trying. If that's the case, you might have to pay some slight fee for repair but you'll know it's done right and the warranty will still apply.

Ans. to OP: To my very limited knowledge.... NOPE never saw it happen before.
J.

I’ve seen it happen with the Smith 22’s, no experience with Smith centerfire AR’s. As always the internet jumps in and blames Bubba for any and all problems, unless the firearm is a Glock or a Taurus. A few years ago there was great resistance to the thought that the 22’s were slam firing. Until Smith admitted that it could happen.

What Hair-Triger said! The previous owner probably thought he/she would do a "home trigger job" at the dinning room table while watching youtube and removed some metal from the sear/hammer. There are a lot of master youtube gunsmiths out there.

Service rifle shooters probably have had more "slamfires" than anyone else. Here's more than you might want to know.

Fulton Armory FAQ: Slam Fires, Mags & SLEDs; Clint speaks out!

Ive shot the weapon for 43 years Auto and Semi Civilian ...NEVER Heard of such a thing...but as always safety first Muzzle pointed down.

Probably wasn't a slamfire from OP's description of the event. There was a passage of time from the round chambering to the discharge, only after he had aimed downrange and flipped the safety off. A slamfire would have been instantaneous when the bolt closed into battery. He didn't mention loading from a magazine, but single loading an AR is not really easy; if all you want is a single shot, it's much easier to load one round into a magazine and load the gun from there.

I shoot a M1A quite a bit, and they have somewhat of a reputation for being slamfire prone if single loaded, or if primers aren't fully seated in the case. Although I've heard tales from some shooters, I've never experienced one myself, even though I have single loaded many times. I just never drop the bolt from the locked open position.

I’ve been shooting ARs for quite a few decades and I’ve never encountered an occurrence like that.

Smith&Wesson has a “lifetime service policy”, and I urge you to contact the company.

Kudos for keeping the muzzle in the right direction.

Many perfectly safe AR 15's have been "improved" by owners to become unsafe. A new standard weight trigger spring might fix it. A little too much stone work on the sear begets occasional doubles. One fix mentioned is to contact S&W and mention "safety problem". Another fix is simply to replace the fire control group with one of the drop in cartridge style units. You won't be without your banger that way.

Maybe nobody else has heard of, or, see of that happening before, but I have....on a couple of occasions. And, each time it has been from someone messing with the stock FCG. Both times it was caused from stoning/'polishing' the angle on the trigger bar where is contacts the 'notch' on the hammer. Other 'issues' I've seen were from stoning/'polishing' the rear lug on the hammer where it contacts the disconnector. You mess with that angle on a MilSpec trigger and/or mess with the hammer, you're just asking for problems. From multiple unintended shots, to the hammer dropping when the selector switch is moved from 'Safe' to 'Fire", to full 'run-away' until the mag empties. I suppose that it is possible that it could happen with a factory, unmodified, MilSpec FCG, but, not very likely, or very often. Unless you know what you're doing, don't mess with FCG's on any firearm.

You can just replace the parts on yours, hammer spring, disconnector spring, trigger spring, disconnector, hammer, trigger, selector switch, and so on, and your problem will probably be solved. But, if it were me, for piece of mind, I would replace the entire kit and kaboodle with a new MilSpec FCG, or, a new aftermarket FCG of your choosing.

Continue to keep that muzzle pointed in a safe direction, update when you get it squared away, and carry on.

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SIC SEMPER TYRANNIS

I appreciate all your inputs, as I have remanded custody of said suspect firearm to a truly talented and accredited AR15 gunsmith for just a cursory FCG and whole unit inspection. I WILL say that after attempting to get this to occur WITHOUT a round in the chamber, I failed to get the hammer to fall. Seems to only do this when a round is chambered with the action locked open and after I chamber the round and select FIRE, does it occur. That being said, I am worried about the ability to move the selector to "safe" prior to even setting the action back. So... my gunsmith will approach this from two ways: Either contact Smith or just repair whatever is goofed up. I appreciate all the input here. There is a great, vast ocean of experience in this location. Thank you all.

Your friend should have kept the gun and got rid of the woman.

^^^ A common, and tragic mistake.

You didn't mention that initially. If "setting the action back" means cocking the hammer/racking the bolt, that suggests something seriously out of spec in the trigger group/safety. An in spec trigger group [in an in spec receiver] will NOT allow the safety to be "on" with the hammer down. Perhaps some misguided individual "fixed" the perceived problem? Alternatively, some massively bad parts were installed at the factory and someone botched the function check. Or, the receiver is out of spec.

Just for the record, after cleaning, the proper function check for the AR pattern is: hold the trigger back and rack the bolt, allow the trigger to reset and be aware of the force needed to dry fire. Next, rack the bolt, apply the safety, attempt to dry fire; then, move the safety to "off" and dry fire. There shouldn't be a noticeable difference in the force needed to dry fire. If there is, the trigger group needs parts replacement. And: the safety should not be able to be placed "on" with the hammer down/in fired position. You can make that check after the first dry fire.

Whatever you spend to remediate this is well beyond well worth it! You can't sell it like that in good conscience and you can't really use it safely. Spend the money, whatever that is and make it right. The alternative is perhaps a life!

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"You're messin' up my Zen"

Thank you mod34. THat'S why the firearm is in the hands of respected gunsmith here, in these parts to find out what I might do to rectify this situation.
Yes.... I volunteered to let the original owner have it back if he dumped the reason why he got rid of it in the first place. NOT a good trade, having seen the reason in first hand. NOT a good reason at all, actually, I will see this through and keep it. I love the firearm and will spend what it takes to make it safe.

Thanks to all!!

Dave

M&P 15 forum-ers,

Is it possible that the previous owner moved (forced, actually) the safety from fire to safe when it was not supposed to me moved? Might be enough to let the sear slip when it is not supposed to.

Zmam10915, congrats on the new-to-you M&P and I'm sorry to hear about the unpleasant surprise at the range. Please post an update once your smith has put things right.

Chris

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/at least she finds me handy.

Short answer: NO! Should not be possible, unless there are some seriously out of spec parts in the trigger group. Or possibly an out of spec lower receiver.

The sear on the AR design semi auto trigger group is on the front end of the T shaped trigger. When the hammer is forward, the design of the hammer blocks the front end of the trigger from moving up. This causes an interference between the safety shaft and the rear of the trigger that keeps the safety from being put in the "on" position. There's a flat on the shaft that allow trigger movement when the safety is in the "off" position, but only with the hammer in the cocked position held by the sear.


I tried to do a diagram of the trigger layout but the cotton picking website won't move the diagram to the thread without distorting it.

I didn't see this in the previous responses:
Did you call S&W? They will fix this for free.

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Freedom isn't free.

Post #16. Ya can lead a horse to water............................................

Zman10915:


Dave, I hope you let us know how this all ends up. This has been a real interesting thread.

Dave,

I just saw this post today. I have heard of similar discharges over about 30 years of competition. It hasn't happened often, but once is two times too many. In the instances that I am aware of, it was a blown primer that got wedged in the FCG. Sometimes, the blown primer gets caught between the sear contact surfaces, and when the safety is disengaged, the hammer slips free.

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