almost new M&P 15 Sport jamming

[smlake]

I recently purchased a M&P 15 Sport. I have had some problems with the gun jamming. I am using the stock pmag and bushmaster 30 round magazines that came with the gun. I am shooting Remington PMC factory .223 ammo purchased from Walmart. I have fired the gun about 80 -100 times. If the bolt and receiver are not well lubricated with Breakfree CLP or Rem oil (or other such lubricant), the gun will jam. Specifically, the gun will lift the cartridge from the magazine but will not push it into the chamber. The cartridge will get caught between the bolt and the chamber. The cartridge case will be well dented near the shoulder so bad the cartridge will have to be discarded. This problem happened about 1 in 3 rounds when the gun was first fired. It now happens about 1 in 8 times. Several shooters of ARs at my gun club have observed this problem with my rifle and tell me the gun just needs to be shot in rather than sent back to Smith and Wesson for repair. The fired cartridge cases have observable scratches on the case necks and the case bodies. I am interested in getting readers opinions and advice. Also, what 3 shot groups are reasonable at 100 yards? Thanks in advance.

 

[JaPes]

If the bolt and receiver are not well lubricated with Breakfree CLP or Rem oil (or other such lubricant), the gun will jam.

You answered your own question right there. AR's function better wet. Lube the bolt , and BCG rails.

Also, the 15-Sport is a tad over gassed. Install an "H" or "H2" buffer and see if it cures your harsh ejection problem.

 

[wihunter]

Spikes ST-T2 buffer and a blue Sprinco spring. Run it wet.

 

[Splittiebus66]

double post lol

 

[Splittiebus66]

Get a heavier buffer when you can....


Oil the cam too

 

[SSgt M]

Where do your ejected rounds land ?

 

[smlake]

The ejected cases land in a very small area, 3-4 ft diameter circle, about 10 feet from the shooting position. The cases land to the right rear from where I am shooting- at about a 4 o'clock position if the muzzle was at 12 o'clock. I am shooting off a concrete bench rest using a padded blanket over the concrete with the rifle being rested on sandbags for stability.

 

[Dragon88]

Where does the bolt come to rest against the cartridge? Behind it, still trying to push it up the ramp, or does it override the base and come to rest against the body of the case?

Is the gas key on your bolt carrier loose?

Is your gas tube loose where it connects to the front sight base?

Is the gas tube off center or not coming back far enough in the upper receiver? Compare with pictures of other ARs on a google image search.

Have you tried a different brand or lot of ammo?

Are all three gas rings present on the bolt? Any deformation or damage?

Any obstructions in the receiver extension, aka buffer tube?


Ignore the "advice" above to get a heavier buffer until you find out the real cause for your malfunction.

 

[papershooter]

Wow...I just posted the same thing up. Having the same issues. Im thinking it's possible I didn't lube the bcg wet enuff to my rifles liking.

 

[GMC man]

Where does the bolt come to rest against the cartridge? Behind it, still trying to push it up the ramp, or does it override the base and come to rest against the body of the case?

Is the gas key on your bolt carrier loose?

Is your gas tube loose where it connects to the front sight base?

Is the gas tube off center or not coming back far enough in the upper receiver? Compare with pictures of other ARs on a google image search.


Have you tried a different brand or lot of ammo?

Are all three gas rings present on the bolt? Any deformation or damage?

Any obstructions in the receiver extension, aka buffer tube?


Ignore the "advice" above to get a heavier buffer until you find out the real cause for your malfunction.

I would also add to the above make sure the gas rings are not aligned the gaps should be staggered and spray some lube in the mags as well.

 

[Wolffire99]

AR's like to be run wet. Not dripping, but close.

 

[Dragon88]

The alignment of the gas ring gaps doesn't matter at all. Also, lube in the magazines not only collects grime, it can be dangerous. If too much lubricant is transferred to a case body before it chambers, this condition can drastically increase rearward force on the bolt during firing, leading to damage or personal injury.

 

[GMC man]

I am not talking dripping wet. I place a very small amount to help the plastic carriage inside ride smooth especially with a new mag I learned that trick in bootcamp from my senior DI and I haven't had any problems with it either in the Corps or now. You don't use any more lube than what you would spay on a cloth to dust with

I have 4 mags two from s&w and two from colt for the 16 and they all was a little sticky until I did that and after 1200 rounds still no problems with the mags or oil on the rounds.

Here is a interesting article on mags:
Extreme Duty AR-15/M-16 Magazines from D&L Sports, Inc.

 

[Dragon88]

Yes unfortunately dated practices in the military build a lot of bad habits about firearms maintenance, and oil in the magazines is just one of them. The gas ring alignment myth is another.

One of my Drill Sergeants in basic told me he put CLP on his ammunition to make sure the rounds fed well. Just because it came out of a DIs mouth doesn't make it good advice.

 

[GMC man]

Yes unfortunately dated practices in the military build a lot of bad habits about firearms maintenance, and oil in the magazines is just one of them. The gas ring alignment myth is another.

One of my Drill Sergeants in basic told me he put CLP on his ammunition to make sure the rounds fed well. Just because it came out of a DIs mouth doesn't make it good advice.

I agree with you about believing everything out of a DI's mouth lol but in the article I posted I was having the carriage getting cocked on me like in the top left picture and that did stop that problem and it was the same thing in boot camp. But at the same time I do see your point about over lubing especially the dirt and getting excessive oil on the rounds is a big no-no.

 

[SSgt M]

Gas ring disalignment is still taught during assembly and cleaning in my last 3 duty stations over the past 16 yrs. Though I've read this argument on every major forum.
If this is the case, it's neither rite or wrong.

 

[Dragon88]

Who is this that's teaching to stagger the gas ring gaps? Probably guys who were told the same thing at their last duty station, and don't know enough to question it.

Align your gas ring gaps and shoot the AR, try to create a malfunction. Let me know when you do. I won't be holding my breath.

 

[GMC man]

Who is this that's teaching to stagger the gas ring gaps? Probably guys who were told the same thing at their last duty station, and don't know enough to question it.

Align your gas ring gaps and shoot the AR, try to create a malfunction. Let me know when you do. I won't be holding my breath.

directly out of the S & W manual:
Assemble your rifle in the reverse
order that you took it apart.
• Make sure that the gas-rings
on the bolt are NOT aligned
when reassembling. (Figures
64 & 65)
• Lubricate all metal parts by
wiping them with a cloth
dampened with a high quality
firearm oil. Remove excess
oil. Leave a light film of oil on
all metal parts of your rifle -
inside and out.
• See page 29 for details regarding the piston driven variation
and its unique instructions

 

[Dragon88]

And you think S&W is the authority on ARs? They are just repeating the same myth, started by the same sources, we've been talking about.

Again, align the gas rings and shoot the thing. Stop believing rumor and test it yourself.

 

[SSgt M]

Who is this that's teaching to stagger the gas ring gaps? Probably guys who were told the same thing at their last duty station, and don't know enough to question it.

Align your gas ring gaps and shoot the AR, try to create a malfunction. Let me know when you do. I won't be holding my breath.

CATAMs instructors, aka military gunsmiths.
Combat Arms Training And Maintenance.

As Per AF TO/ARMY TM
I will try and find a copy to see if it's still in there.