AR15 woes

[standingbear]

all you AR15 gurus out there..my E2S stopped working and heres the scoop.

worked fine in the past ,course,Ive always used American eagle or the plain white box 55 grain ammo.today,my nephew bought a bunch of S&B ammo and we plinked away till after 200 rnds..it started to have "failure to eject" problems.It was almost like not enough gas was getting into the key to push the bolt back far enough.it would grab a round and fire manually ok but wouldnt kick out the shell casing all the way unless it was cycled manually.

-stopped shooting and brought it home and gave it a good look see.the key on the bolt was just a little loose and slight turn with the allen wrench got it tight again.was not too dirty and I know the mags were all good mags.not sure about the ammo and why the key came loose.

so,heres my questions..

-any issues with S&B ammo?
-why did the carrier key come loose and how can I prevent it from loosing up in the future?
-any other tricks to keeping it working?

 

[nhhillbilly]

Stake the Key

Tighten the key and stake it. That should solve the problem.

 

[Darkside]

Ditto on what nhhillbilly said. That should fix wour problem. Stake it, then give us another range report.

Darkside

 

[JNewell]

Agree with posts above. The loose carrier key could definitely be 100% of the cause (and cure) for this. Stake 'em, don't even think about thread lock compounds.

 

[Badger Arms]

I've had this happen on two different guns from different manufacturers. Tighten the heck out of it with locktite and then stake the crap out of it. It's a fairly common problem and a

HUGE FLAW IN THE DESIGN

that one of the main parts in the gas system is both fragile (ever bent the front of the gas key) and prone to loosening. If it were HK, they would have welded that sucker on there and made the nose of the key much stronger.

crouching behind cover for fear of getting flamed...

 

[JNewell]

Badger, what makes of rifles? If it's staked to milspec, there should be no problem, but that means a serious upset of the carrier key screws.

 

[standingbear]

well...bought some RED loctite..the kind that takes heat to remove.Put 1 drop on each threaded portion of the hex screws and tighten'd it to the point it just wouldnt turn anymore.let it set 2 days and took it out & fired 500 rnds..no more problems(still hadnt cleaned it from the original 200 rnds)checked the key hex screws and they hadnt budged.incidentally,the key had been factory staked on originally an in my curiousity....I broke the gun down completely to learn how it went back together and worked.

I still dont know why the key is a seperate piece in the design of the bolt,the bolt assembly can be rotated to the left and slid out the side of the bolt carrier and a blast of carb cleaner and a pipe cleaner cleans it out pretty durn good.

the only other thing that would be a nice addition would be to have the spring retainer built as a threaded ring in the stock rather than the small knob that sticks up from the rear lower receiver an continually takes little chuncks out of the bar thing in the stock.Its "normal wear" I know but seems alot of stress centering on that little knob from the spring in the stock.

 

[Darkside]

I often thought that a simple lock washer would work to keep those screws tight. I know it would just be more parts. Once those screws are staked they rarely come loose.

Glad to see you are up and running.

Darkside

 

[JNewell]

bought some RED loctite

Be advised, even red loctite will not provide long-term reliable attachment of the key to the carrier. The key screws need to be physically upset by staking per the milspec for assured reliability. If this is only a casual use weapon, that will not be a significant factor, but if you could need the rifle for defense or even if you only use it in competitions, you may want to follow the milspec.

 

[standingbear]

the loctite is "271" and supposedly it takes between 3-400 degrees to heat it up nuff to break the seal.I dunno.It was the strongest stuff they had at the auto store aside from welding it

running like a champ now anyways,I may have it staked later if it comes loose again.Id stake them myself but I dont want to permanently damage the screws.its a casual use gun..nothing special.

at least I know now how the gun works and what to watch for.

 

[Darkside]

I can't remember if the screws have the stake marks or the bolt. But I think with a little care you could "restrike" the exsisting marks and wouldn't create any "new damage"

I would do that before relying on the locktite. Even if it is a range rifle, I wouldn't take the chance of having the key come loose again and possibly doing damage internaly.

Darkside

 

[JNewell]

I dont want to permanently damage the screws

<smiles> That's precisely what staking is all about -- they are removeable but essentially permanent (if staked correctly) until removed, and then should not be reused.

at least I know now how the gun works

A very good thing! Enjoy.

 

[RJ357]

the only other thing that would be a nice addition would be to have the spring retainer built as a threaded ring in the stock rather than the small knob that sticks up from the rear lower receiver an continually takes little chuncks out of the bar thing in the stock.Its "normal wear" I know but seems alot of stress centering on that little knob from the spring in the stock.

That's the buffer retainer. And as you can guess the bar thing in the stock is the buffer.

Is the little pin on the retainer getting bent at all from the buffer? The buffer really should not be contacting the retainer at all except when the upper receiver is open. The rear of the bolt carrier should push the buffer off of the buffer retainer pin slightly when the upper is closed. If the little pin is not bending it is probably OK. But if the buffer is getting worn away, it sounds like it is hitting it some.

 

[RJ357]

Since you described it as a "small knob", it's got me wondering. Does the buffer retainer look like a small cylinder with an even smaller pin sticking up out of the top?

 

[standingbear]

But if the buffer is getting worn away, it sounds like it is hitting it some.

yup..nice little ridges all the way around the aluminum buffer edges...you mean it shouldnt do that?

the pin isnt bent as far as I can see.it clears the groove in the bolt bottom as the bolt travels back and forward...no wear at all in that channel under the bolt.aside from those ridges on the buffer..the gun looks new inside and out an its been shot quite alot of times.

I did look closly at the buffer as I closed the upper down with the carrier locked.it did move the buffer back just a wee bit.

geesh..this is starting to make me wonder now.

 

[RJ357]

As long as the bolt carrier pushes the buffer off of the buffer retainer, with the bolt fully closed, It should be OK.

It should be the carrier that stops the buffers movement forward and not the retainer (in operation). If the little pin stops the buffer before the carrier is fully forward, it will eventually bend or even break off. That could occur if the hole for the buffer retainer was drilled too far to the rear.

Just to be sure, what you should have, is the larger diameter part of the retainer sitting completely down in the hole. The buffer tube should extend into the lower receiver just enough to partly cover the hole that the retainer sits in (the buffer tube is what the buffer rides in. The stock also slides over it). So the larger part of the retainer is trapped under the front edge of the buffer tube. Then the smaller diameter part of the retainer extends up past the edge of the tube.