AR malfunctioning

[masshole42]

Hello. I am new to this forum and am not sure if there is another post regarding a similar issue so my apologies if its redundant. Anyways I have a Bushmaster XM-15 that is having issues with fte and ftf. I never had problems before. Anyways I bought some Federal XM855 and M193 to shoot. I went through 4 mags(only 40 rounds since I live in MA) with no issues. Each round went bang and the bolt locked back on last round. My brother then loaded the rifle, fired the first round, then said it jammed. It was a fte. I proceeded to clear the malfunction and fire the next round. Another fte. Cleared that malfunction and then after that it was nothing but trouble. The malfunctions consisted of fte where the case would not fully eject and the bolt would jam halfway closed. The other malfunction was ftf where the case would eject but the bolt would close on an empty chamber. I tried cleaning and lubing the BCG and bolt with no effect. I am stumped. I'm familiar with the basics on my rifle, but in no way I am expert. The only modification I've done is a BCM extractor spring upgrade. Other than that everything I put on is purely cosmetic. It's a 16 in. barrel with carbine gas system. Stock buffer spring with a rifle buffer(came with rifle buffer, but I did purchase a carbine buffer). Any help would be greatly appreciated. Thanks.

[5pins]

It sounds like its short stroking. The first thing I would check would be the gas key and make sure its not loose.

[masshole42]

I did check the gas key and it was tight.This is the first time shooting 5.56 through my rifle, and I read that sometimes even though a rifle says it is chambered for 5.56 the measurements can be off. I'm hoping this isn't the case, and I don't believe it is since I was able to shoot a few mags reliably before the failures started to occur. My theory is that the bolt is moving too fast and the extractor is slipping off of the case causing it to not fully eject, and then in turn when the bolt attempts to close the spent case becomes jammed. I am no expert so that is just my theory. Would a heavier buffer or stiffer buffer spring slow down the BCG?

[landshark]

Few questions first:

1.) Is this a new rifle? As in these first 40 rounds through are the first rounds put down range?

2.) If question one is true, I would have to ask why throw in the BCM extractor spring?

3.) When you say FTE are you saying Failure to Eject (Brass does not fully leave weapon) or Failure to Extract (Brass is half/still stuck in the chamber)?

[AR-10]

Yes a heavier buffer will slow down the cycle, but that doesn't seem to be the problem.

How many rounds total have you put through this rifle?

If you are sure the gas key has a good seal on the carrier, I'd be looking at the gas rings on the bolt.

Something either wore out or came loose in the middle of your session, I doubt it's a buffer weight issue.

[AR-10]

I just realized you said you replaced your rifle buffer with a carbine buffer - you need to expand on that.

First of all, what buttstock do you have?

[Stickman]

if nothing was changed between it working, and handing it to him and it not working, check the carrier key for obstruction. I've seen primers pop out and get caught in there. They are a pain, and can be hard to see.

While its apart, check the rings and carrier key to make sure it is tight and hasn't come loose.

[Eric]

The only modification I've done is a BCM extractor spring upgrade. Other than that everything I put on is purely cosmetic. It's a 16 in. barrel with carbine gas system. Stock buffer spring with a rifle buffer(came with rifle buffer, but I did purchase a carbine buffer).
Did the malfunctions begin after you changed something? If you have the o-ring in place with the BCM extractor spring, try removing the o-ring.

Keep in mind that if you have a rifle size receiver extension (buffer tube) which typically has a fixed stock (A2, A1) you must use the rifle buffer. Rifle and carbine buffers are specific to their respective receiver extension. If you're looking at converting to a carbine setup, you need to change out the receiver extension, buffer and stock (and a few other small parts). Bushmasters are typically over-gassed. If run with the carbine stock, an H or possibly an H2 buffer is recommended.

Do you have a fixed front sight assembly or a gas block?

[landshark]

I just realized you said you replaced your rifle buffer with a carbine buffer - you need to expand on that.

First of all, what buttstock do you have?

+1
Its odd to me that Bushmaster would send out a weapon with a rifle buffer with a carbine buffer tube on the gun. If you XM-15 is the ones that I am seeing pics of with my google-fu, then unless you got it used it is unlikely that it had a rifle buffer in it. Not to insult your intelligence, but for reference:

http://i38.photobucket.com/albums/e106/Captains1911/paper%20punchers/BufferSpringInsp.jpg

Which do you have and then what type of buttstock like AR-10 said?

[masshole42]

I'll try to answer all of your questions: I bought the rifle used. Not sure how many rounds were put through it before I bought it but it looked as though not a whole lot. I have the standard adjustable butt stock that came with the rifle brand new(as far as I know). As for round count, I don't know exact numbers but I probably put close to 1000 rds or a little over through it. I bought the carbine buffer and BCM spring upgrade after doing some research because I wanted to shoot Tulammo(steel cased, dirty, underpowered, yada yada I know, but with those two changes my rifle cycled it flawlessly) I did not have the o-ring insert on the extractor spring when I had the malfunctions. As for fte, I'm not entirely sure. There were times when the case ejected properly, then other times it seemed like the case would extract from the chamber but not eject since the bolt would jam the case part way back into the chamber so that I am not 100%, sorry. It has the standard A2 front sight post. I did not change anything before the malfunctions occurred. I did check the gas rings. I extended the bolt all the way forward and stood it upright flat on the bolt face and the bolt did not recede back into the carrier so I'm assuming the rings are fine. If there is a better way to check the rings then I will try that.

[masshole42]

No offense taken. Believe me, I had to do research myself to figure it out haha. But yes I did buy it used and it was a rifle buffer that was in it.

[masshole42]

To clarify further, its a standard M4 style butt stock

[Stickman]

So you didn't pull the BCG apart and check the carrier key?

[AR-10]

It has an M4 stock but it came with a rifle buffer?

Pull out your action spring and buffer and take a pic, please.

[nub]

I had a bushmaster with a similar problem, turned out that the GB was leaking.. I figured it out when I noticed carbon on the GB.

[masshole42]

Yes it has a M4 stock and yes it came with a rifle buffer(bought it used). I did check the carrier key when I was at the range and it seemed tight, but I will check again when I have the chance. I will post a pic of the spring and buffer when I get the time to sit down and figure out how to do it on my phone.

[AR-10]

I think you're confused about buffer types.

If you have a collapsible M4-type stock, you have a carbine receiver extension which takes a carbine action spring and a carbine buffer.

The rifle counterparts are longer, If you tried to put a rifle buffer in a carbine receiver extension, I doubt it would even cycle.

[masshole42]

I understand that. But unless there is another buffer that is identical in looks and length to a rifle buffer, a rifle buffer came in it. I'm not trying to be a smartass, I really don't know if there is another similar buffer. As for cycling, I ran PMC Bronze and Federal .223 100rd bulk pack through it and it cycled fine. The only reason I ran the carbine buffer was to shoot Tula and it cycled flawlessly.

[AR-10]

I'm not harping on you at all, just trying to make sure you have the correct buffer parts.

Post a pic when you can, I want to see the buffer and spring.

[masshole42]

Well I have a picture, but I cannot attach or upload it for some reason so you will have to take my word for it that it is a rifle buffer. As for the spring, I decided to measure it....and found out something interesting. It measured 12 3/4 inches. I'm assuming it is a rifle spring. Why that is in there I don't know. I feel pretty stupid not checking the length of the spring when I first realized it had a rifle buffer. At least now I know I need to get the proper spring. I know I need to get a new spring anyways, but would this be the issue for my malfunctions? If so, why would it cycle for the first few mags and then crap out? For a new spring, any suggestions on a quality spring or will a standard one be fine?

[FortTom]

If you have a rifle spring and buffer, you'll need to change both, not just the spring. Refer to the pic's that were posted above. If your spring is 12.75 in long, and your buffer looks like the one posted above, the bottom one in the picture, in a carbine stock, I'm suprised it even cycles at all.

It would really help if you could find someone to post some pics for you. I'm sure someone will spot the problem right off. Also, why did you change the extractor spring? Did the problems start after that? What problems were you having before you changed the spring?

FT.

[masshole42]

As for pictures are you referring to pictures of the malfunctions? I changed the spring because I wanted to shoot Tula and my first experience didn't go so well. I read that steel cases expend different from brass cases so I decided to try upgraded the spring to be able to eject the steel cases. It helped but didn't make it 100% so that's when I bought a carbine buffer and then my rifle would cycle the Tula 100% as well as the Federal .223 brass cased ammo I put through it. Besides the trial with the Tula, my rifle never malfunctioned until now, which was after 40rds of a combination of M855 and M193.

[csmith]

I believe he meant pictures of the spring and buffer.

[Paulo_Santos]

Just measure the buffer.

[FortTom]

Yes, I was referring to the pictures that were posted avove of a carbine spring and buffer on top and a rifle spring and buffer right below it. Or if you're having a hard time locating it in this thread, do like Paulo said and just measure the buffer and post the measurement in thie thread.

FT

[AR-10]

I've never had a problem with steel cased ammo and I use $5 BCM springs with H buffers.

If your action spring is questionable I would replace it with a new spring and I would also buy one of each buffer weight to keep in the range bag.

[masshole42]

ok i measured the action spring again and the buffer. The action spring was 12.75 inches and the buffer was 5 7/8 inches. So the conclusion is that I have a rifle spring and buffer. How is my rifle able to cycle with those in a M4 collapsible stock I do not know, but it does. (well, it did.) I purchased a new carbine action spring and H buffer from BCM. When those arrive, I will give my rifle a thorough cleaning and lubing and double check the gas key screws then head out to the range. Hopefully I will make it out sometime this week and be able to report back. Is there anything else I should check before I head out to the range or other things I can check/troubleshoot at the range if it continues to malfunction? I am going to try to pick up a couple boxes of other kinds of ammo. I figure having a wider range of ammo to test couldn't hurt.

[5pins]

Something is not right here. There is no way your rifle will work with a rifle buffer and spring in a carbine receiver extension, there is physically not enough room. The carrier will barely move back at all never mind stripping a round from the mag. I would advise you to take your rifle to someone who can tell you what you have before putting your carbine spring and buffer in it.

[Eric]

Photos would be helpful. www.photobucket.com is a free host that is easy to use.

[masshole42]

http://i1265.photobucket.com/albums/jj506/dhunt42/6088adbc.jpg

My Rifle




http://i1265.photobucket.com/albums/jj506/dhunt42/d6dda3d8.jpg

Action spring and buffer

[masshole42]

Finally I am able to post pictures. Thank you Eric for the heads up about photobucket. I hope these pics help with some of the confusion or at least reinforce the information I have been giving. Like I've said before, it's a rifle buffer with a rifle spring, and to the best of my knowledge that is a carbine receiver extension or am I wrong about that? I would go the distance and remove the butt stock from the receiver extension, but as i stated in my original post I live in MA and this rifle has been "massified" so the stock is pinned and I don't want to battle with that to get the pin out. So I'd rather just leave that alone. If the final conclusion about the parts can be finalized, (rifle action spring, rifle buffer, and carbine receiver extension) then I can say with confidence that my rifle cycles flawlessly when it apparently shouldn't (despite the current issues I am having with it). Since now I can post pictures, if there are any other pictures that anyone would like to see that may help with diagnosing the issue just let me know. When I make it out to the range, I will try to take pictures of any malfunctions I experience (hopefully there will be none).

[AR-10]

That is bizarre, those are rifle buffer parts and you have a carbine receiver extension.

You said you replaced the rifle buffer with a carbine buffer, where is that buffer and did you also replace the spring?

[masshole42]

Yes I bought a carbine buffer. No I did not replace the spring.

[Stickman]

Yes I bought a carbine buffer. No I did not replace the spring.


You need a carbine spring and carbine buffer in a carbine receiver extension (buffer tube). Get a new spring and get rid of your aggravation.

[masshole42]

I did buy a carbine spring as well as a H buffer. When they come in I will get out to the range.

[FortTom]

That is bizarre, those are rifle buffer parts and you have a carbine receiver extension.

You said you replaced the rifle buffer with a carbine buffer, where is that buffer and did you also replace the spring?

Wow, something new everyday. Bizarre is an understatment. But I'm going to take a wild assed guess here. He bought the gun used. O.K, now the stock is pinned to meet Mass requirements, since the stock is pinned back, do you think a middleman somewhere assumed the lenght of the stock, pinned all the way back, indicated the lenght of the tube and assumed it was the same as a rifle stock and tube? Following my logic here? I honestly don't think I've ever seen this one before, it should be "stickied" to the thread by the mods, just for giggles. (sorry Masshole42) wasn't your screw up, not poking fun at you , but it was someones major screw up. I personally don't see how the thing cycled at all, but I guess it did, somehow. O.K., Masshole, you'll look back and have a good laugh about this, someday, just probably not today.[:D]

FT

[masshole42]

This is my first AR and yes I bought it used. I had very little experience with this style of firearm so I didn't really know exactly the things to check out before buying it. I saw it was a Bushmaster, (which isn't the best quality AR out there, but good enough quality for my purpose), it was already "massified," and the price was right so I bought it since I've wanted one for awhile now. Took it out to the range soon after with 100rds of PMC Bronze .223 that I bought with it and it shot flawlessly. I had no reason to suspect there was wrong parts in it. The beginning of my research and education on the AR platform rifle didn't start until I started trying different ammo. (ie Tulammo). This was after I put close to 400-500 through it with no malfunctions. So I did research on buffers and springs and that's when I did the couple changes.I realized it had a rifle buffer in it which I found odd, but just went with it since I never had an issue. I never thought to measure the action spring since I had little experience so I was just under the assumption it was the correct one. So yeah...I'm glad I can make some people scratch their head in disbelief, LOL

[5pins]

This is a picture of a rifle buffer in a carbine buffer tube. This is as far back as the BCG will go. Obviously there is no way this will work, and there is no way the OP has a carbine receiver extension. If I were to take a wild ass guess, the OP’s carbine really has a rifle length RE but made to look like a carbine stock.

https://lh3.googleusercontent.com/-Le6SoN3dGrg/UFefSqZtQ0I/AAAAAAAAAAY/uaR06_j9M-I/s648/20120917_175108.jpg

[csmith]

If I were to take a wild ass guess, the OP’s carbine really has a rifle length RE but made to look like a carbine stock.

Simple way to figure that out. masshole42, would you mind looking down your buttstock and commenting on if the tube is actually flush at the end of the stock opening? I'm basically looking for a measurement of the buffer tube.

[masshole42]

So after all, I believe 5pins has been right all along. I was able to get a rough idea of the length of the tube. I stuck a piece of an arrow into the receiver extension and then marked on the arrow the end of the threads. I then measured the tip of the arrow to the mark and got about 10in. So I'm assuming this a rifle receiver extension? Sorry for the poor quality pictures. I don't have the best lighting in my room. At least you can get the basic idea.


http://i1265.photobucket.com/albums/jj506/dhunt42/834542e6.jpg


http://i1265.photobucket.com/albums/jj506/dhunt42/44f7f498.jpg

[AR-10]

If that is the case then you need to stick with a rifle spring and buffer.

I have never seen an extended carbine receiver extension, but apparently they do exist.

[masshole42]

Well I definitely found out some interesting facts about my rifle. So I guess I'm back to square one.

[masshole42]

Hey all, I just wanted to post an update. I was able to locate the cause of the malfunctions and correct it and now my rifle shoots flawlessly like before. It turned out that the gas key was in fact loose the slightest bit. I tightened the screws down and it cycled like a dream. I feel quite stupid for not checking the gas key more closely when it first began malfunctioning. 5pins said it right at the beginning and I failed to take a closer look so my apologizes to dragging out this thread a lot longer than it needed to be. I do want to thank everyone for the help and suggestions. I did find out new information about my rifle, such as it having a rifle receiver extension, that I probably would have not found out. Anyways I just want to thank everyone again for the help and support.

[csmith]

There wouldn't happen to be a brand logo anywhere on the extension, would there? I'm just curious to see a rifle extension made for a carbine.

[masshole42]

From what I could see there isn't one. If there is one covered by the stock I would have no way of knowing since the stock is pinned.

[5pins]

I was at a local gun store and saw to carbines with rifle extensions like the one masshole has. I have never seen one before but I just moved to a ban state last month so I better get used to it.

[AR-10]

Stake your gas key and the screws should stay tight:

http://www.weaponevolution.com/forum/showthread.php?1613-FAQ-s-BASIC-INSPECTIONS-AND-PROCEDURES&p=21560#post21560

[Xrugger2012]

First I would check to ensure the three rings on the bolt do not have the open spot in the same place, if they are, seperate them to roughly 1oclock , 4 oclock, 8 oclock. This seals the bolt, replace the Rifle buffer. Run some rounds through to repeat the failure. if it still fails there is a gas leak somewhere.

[Eric]

First I would check to ensure the three rings on the bolt do not have the open spot in the same place, if they are, seperate them to roughly 1oclock , 4 oclock, 8 oclock. Nope. When the bolt is inserted into the carrier there is a slight taper which compresses the gas rings, closing up the gap. Even if you stagger the rings, they move around during firing and can line back up. Not that it's recommended, but the system will function with a single gas ring.

[Xrugger2012]

Yup Wrong Spring and Wrong Buffer.

[Eric]

It turned out that the gas key was in fact loose the slightest bit. I tightened the screws down and it cycled like a dream. To properly make the repair, new screws should be used. They need to be torqued to 50-58 inch pounds and staked in place. If you need assistance with getting it done PM me.

[masshole42]

xrugger- The spring and buffer are correct. The gas key was the issue.

Eric- I was able to make the repair, thank you for your offer to help.