almost brand new M&P 15 sport not wanting to fire

[cjpitt1985]

ok this is the best way to describe my problem. A few months ago I bought an M&P15 sport. I then directly took it to the back of the store without cleaning it and put 60 rounds through it fine.

So I took it home, cleaned it pretty thoroughly, lubed it, and now it will chamber rounds, fire them, and then in the middle of a magazine every once and a while "click" and no boom. I have to rack the round out of the chamber and the crimping is loose on the rounds at the end of the casing. This was with both American Eagle 5.56 55gr rounds and Perfecta .223 55 gr.

This has happened on two different trips to the range. The first time I even had to take the upper/lower apart because a round got "stuck" in the chamber crooked. Today, I had a couple of misfires out of the first mag but then I ran 50 rounds out without any issues. I wish I would have brought more ammo out there because it wasn't malfunctioning for the last 50 but it still bothers me. And I don't blame the magazine because it happened with two different magazines the first trip and they are all brand new P-mags.

Could this be a "break-in" thing? I just find it odd that straight from the box I fired 60 out of it without any issue and now that I have it cleaned and lubed a lot better it is having issues. I know it is reassembled right and the gas ring notches aren't lined up either.

Should I send it in or give it more time?

 

[JaPes]

It doesn't sound like a break in thing to me.

Have you field stripped the bolt carrier and cleaned it? Are there any obstructions that would prevent the firing pin from free floating in the BCG? Hinge open your upper and lower. Look for any odd witness marks on the lower, in the upper receiver, on the BCG. See if something is dragging.

That's about as far as I would take it, then I would call S&W CS.

 

[cjpitt1985]

It doesn't sound like a break in thing to me.

Have you field stripped the bolt carrier and cleaned it? Are there any obstructions that would prevent the firing pin from free floating in the BCG? Hinge open your upper and lower. Look for any odd witness marks on the lower, in the upper receiver, on the BCG. See if something is dragging.

That's about as far as I would take it, then I would call S&W CS.

yes I've completely taken apart the BCG and cleaned it with solvent and oiled the hell out of it before both times it had malfunctions. There's no obstructions or anything I can find. Looks like an AR-15 should look inside. I've even cleaned the buffer tube. The only thing I haven't done is mess with the gas system but I don't think it is obstructed or it wouldn't run at all.

I'm a pistol person, kinda new to semi-auto rifles, so I'm not all that familiar with it (why I got a sport because I didn't want to spend a fortune on something that I was just getting into).

 

[JaPes]

Sounds like you're using good firearms common sense in diagnosing your issue.

Call S&W. Better to be safe than sorry. I'd be wary of an out-of-battery primer ignition or any other problem.

 

[cjpitt1985]

Yeah I figure I'll call them and send it in. From what I've been reading it could be that the chamber is not sized right to fit the round possibly?

I don't know but at almost 50cents a round to try to "break it in" it isn't a cheap diagnosis. I figure I'll let them figure it out on their dollar considering one of the biggest reason I like S&W is their good customer service.

 

[scooter123]

Your Bolt Carrier should be BONE DRY except for the rails that locate it in the receiver. If you are lubing the Bolt inside the Bolt Carrier that is a PROBLEM. That lube will collect powder residue and create a Gum.

I would also suggest soaking the bolt for a while and using toothpick or similar items to totally clear the channel for the Firing Pin. Because if you've been lubing this area it's likely that it's become packed up with something that resembles Tar and gumming up the firing pin.

Tip, when assembled with the firing pin locked in place by the retaining pin you should be able to hear the firing pin rattle back and forth as you shake the Bolt Carrier group. If you can't hear that rattle, start over and get everything cleaned properly.

PS: they aren't cheap but a Nickel Boron plated Bolt Carrier can allow you to run your AR15 without ANY lube at all. This means us Belt and Suspender types can use a very light application of oil to the rails and not see any wear in the receiver.

 

[MichiganScott]

My experience has been 180 degrees opposite scooters. I run my range guns wet. When I shot local marches competitively, I'd start the season with the bolt and carrier wet almost to the point of excess. After each match, I'd place a couple of drops of CLP in the vent holes of the bolt carrier. The gun wouldn't get cleaned until after the season, which could be as much as 600 rounds. Never had a misfire.

I don't believe in "break-in" periods. If a firearm is put together and designed with proper tolerances, it should run from the first shot. I do realize that occasional burrs from the manufacturing process may need to wear off, but more than a couple of hiccups when you first shoot it is unacceptable.

 

[walkin' trails]

I'm with Michigan and run my ARs with the BCG wet. For what it's worth, the been-there-done-thats who are teaching today say the same thing when dealing with stock ARs/BCGs. I have no experience with the advances coatings, but I would suggest you get with S&W and the the gun running in stock form like it's supposed to before investing any more money.

 

[m1gunner]

If your AR has a 5.56 chamber, do your breakin with M193 ammo. It is full power and will run the rifle as designed.

Take your chamber brush and some Hoppes #9 and scrub the chamber, then dry with several dry parches.

And run the bolt carrier assembly dripping wet with CLP. A dry BCG, a new gun, and underpowered ammo will turn any AR into a jamm-o-matic.

 

[cjpitt1985]

The American Eagle 5.56 is m193. It is dripping wet in Hoppe's 9 lube. The bolt, the bolt carrier, and I even put a tad on the firing pin. Hoppe's 9 has worked for every other firearm I've ever had. Scooter's theory about having a dry bolt doesn't add up because this thing jammed up on the 3rd shot of m193. It was lubed but it was 100% clean. In fact it had problems when it was clean, but the last 50 rounds shot off without a hitch.

I'm calling S&W today and having them shoot it on their dime until they get it right. I didn't do anything wrong and it is all brass, decent ammo that should be going through.

 

[bhayles]

My experience has been 180 degrees opposite scooters. I run my range guns wet. When I shot local marches competitively, I'd start the season with the bolt and carrier wet almost to the point of excess. After each match, I'd place a couple of drops of CLP in the vent holes of the bolt carrier. The gun wouldn't get cleaned until after the season, which could be as much as 600 rounds. Never had a misfire.

I don't believe in "break-in" periods. If a firearm is put together and designed with proper tolerances, it should run from the first shot. I do realize that occasional burrs from the manufacturing process may need to wear off, but more than a couple of hiccups when you first shoot it is unacceptable.

I go with this. I have 3 Sports, one with about 4500 rounds thru it, the second with about 1500 rounds thru it, and the newest with 300-500 rounds thru it, and I run all three wet, Wet, WET, WET. All but dripping...

That's around 6000 rounds thru three guns and I've had one FTF...and that was the ammo, not the gun.

 

[Kadonny]

Sounds like we need a lubrication update thread. FWIW, I've been running my Sport pretty wet, but now I'm going to try it drier with the BCG dry except for the rails to see how it runs.

 

[REM 3200]

The American Eagle 5.56 is m193. It is dripping wet in Hoppe's 9 lube. The bolt, the bolt carrier, and I even put a tad on the firing pin. Hoppe's 9 has worked for every other firearm I've ever had. Scooter's theory about having a dry bolt doesn't add up because this thing jammed up on the 3rd shot of m193. It was lubed but it was 100% clean. In fact it had problems when it was clean, but the last 50 rounds shot off without a hitch.

I'm calling S&W today and having them shoot it on their dime until they get it right. I didn't do anything wrong and it is all brass, decent ammo that should be going through.

I also use Hoppe's 9. It's good stuff. However, it is a solvent, not a lube.
I use it to clean and then lube with a product that is a lube.
I like CLP (just short of dripping) as it keeps the crud in
semi-suspension and makes it easier it clean at the end of the day.

 

[gwpercle]

Make certain it is re-assembled correctly...doesn't take much to get them not acting right.
Gary

 

[m1gunner]

In your initial post you said you shot it NIB without cleaning it. These guns have preservative in the barrels that must be removed before putting the gun in service. Once you fire it with this stuff in the chamber, you have semi solid coating that forms.

If the bolt does not seat all the way, it doesn't cam all the way into the lugs, and the carrier blocks the firing pin from being able to go full stroke and set off the primer. This is a safety feature of the design top prevent OOB or partial lockup firing.

It doesn't take much, a resized case on a reload (I know, you had new ammo) where the sizing die does not touch the shell holder will cause this many times, and you can not see the difference in a good round compared to a bad round. So just a little semi-solid crud in the chamber will do the same thing.

Without seeing the gun, this is most likely as the gun was shot with anticorrosion treatment in the bore.

That chamber brush does a good job, try it.

 

[cjpitt1985]

In your initial post you said you shot it NIB without cleaning it. These guns have preservative in the barrels that must be removed before putting the gun in service. Once you fire it with this stuff in the chamber, you have semi solid coating that forms.

If the bolt does not seat all the way, it doesn't cam all the way into the lugs, and the carrier blocks the firing pin from being able to go full stroke and set off the primer. This is a safety feature of the design top prevent OOB or partial lockup firing.

It doesn't take much, a resized case on a reload (I know, you had new ammo) where the sizing die does not touch the shell holder will cause this many times, and you can not see the difference in a good round compared to a bad round. So just a little semi-solid crud in the chamber will do the same thing.

Without seeing the gun, this is most likely as the gun was shot with anticorrosion treatment in the bore.

That chamber brush does a good job, try it.

I know I sound like an idiot, but what chamber brush? I don't recall a brush being in the box.

 

[JaPes]

I know I sound like an idiot, but what chamber brush? I don't recall a brush being in the box.

While I don't agree with the notion that there aren't any stupid questions, your question isn't a stupid question. Until I owned my 15-Sport, I had no idea that an AR-15 chamber brush existed or what it looked like. S&W does not include any cleaning kit in the box.

This is an AR-15 chamber brush.

I affix it to a pistol cleaning rod. I either spray solvent into the chamber or moisten the brush with solvent, then brush away.

I wrote a post on all the AR-15 cleaning tools I own. It has a bunch of pictures and should be very helpful to you. If you have any questions, just ask.

http://smith-wessonforum.com/smith-...8269-new-ars-here-some-tools-i-use-clean.html

 

[JaPes]

One suggestion about making sure the path of the firing pin isn't gummed up or blocked. I don't do it often, nor do I remember the last time I did this.

If the bolt is gummed up with old lube:

1. Remove the extractor. Remove the the rubber O-ring and spring. Set those aside. I don't want the rubber O-ring to get eaten up by step 4.
2. Use the pipe cleaner to clean out the firing pin channel in the bolt.
3. Use the CAT M4 to clean the bolt tail, firing pin.
4. I'll then hose the bolt off with non-chlorinated brake cleaner. I'll then insert the spray straw into the bolt tail and hose out the firing pin channel.

Use safety goggles. Hold the bolt away from you and angled so you don't get splash back. I keep my mouth closed and hold my breath. I do this outdoors.

I'll then use pipe cleaner to clean the firing pin path through the bolt. I'll use pipe cleaner to clean out the cam pin's firing pin hole. I'll use pipe cleaner to clean out the gas key.

Just in case, this is pipe cleaner.

 

[m1gunner]

Yes, the firing pin should move freely in the bolt. Gravity alone should be enough for it to move in or out.

When you do a tear down and inspect the bolt, check that the rings look good and not damaged.

Also, the "flick test" will tell you if your gas chamber is rough and needs breaking in. Basically, take the assembled bolt carrier group and push the bolt into the carrier as far as the cam pin will allow. Then "flick" the bolt like you would a gravity knife. The bolt should extend to the front as far as the cam pin will let it.

Some CLP on the rings and work the bolt in and out will alleviate a tight bolt/carrier fit.

 

[WR Moore]

Please explain the phrase "the crimp is loose at the end of the casing". Do you mean the bullet crimp or the primer crimp? If bullet, it hints at a feed failure of some type. This is generally a magazine issue. Note: AR magazines should be downloaded 2 rounds from full capacity for reliability reasons.

OK, I have to agree that taking a brand new firearm to the range without prior cleaning and lube is asking for problems. If you ran 60 rounds through it without issue, there's no issue with the chamber.

I've been using the AR system for ~40 years and I'm not a wet bolt type. I haven't worked in the sand box, but in all other environments, I've gotta go with a modified version of Scooters suggeston. The rails the carrier runs on should be lubed. The rest of the carrier body only needs enough lube to prevent rust. Note that I use the word "lube", not oil. I prefer a dry film lubricant so that the combustion gases don't turn it into carbon. However, others have been successful with other products. I do like to use moly grease (chassis lube) on the cam pin surfaces of the carrier-a little dab will do ya here.

The firing pin should run back and forth by it's own weight as someone else noted above. Do the bolt cleaning as JaPes suggests.

Since you noted you've "lubed the hell out of it", I suggest removing the buffer & spring and remove excess lube/oil/**** from the buffer tube/receiver extension. Look down in there and make sure nothing lurks in the tube to limit buffer travel.

IMO, the nylon chamber brushes outlast the bronze ones and are worth the slight extra cost. The "one product cleans, lubes and protects" stuff is beloved of those who manage supplies and/or carry all the stuff on their backs through the boonies. They're generally not as good as a product specifically designed for cleaning, or lubing or protecting.