My carbine (Bushmaster M4 14.5 perm Phantom, a LaRue 13.2 rail, and an Eotech 512, with all internal parts as they were from the factory) has shot over 2,000 rounds without a failure prior to this incident. However this time I was shooting Guatemalen ammo, the new shiny stuff that AIM is selling now.
The problem happened when using a British Steel mag with green follower. It only happened twice (out of 270 rounds fired total) and both times with the same mag. It occured when loaded with just 5 rounds, and when laoded to full capacity.
The jam can best described as an FTEj. The spent round is stuck with the rear against the bolt face, and the front stuck up in the charging handle channel. The bolt is also in the process of stripping a new round off the mag but cannot go farther due to the spent case obstructing its forward travel.
I’ve looked and looked and searched, but haven’t found any problems similar to mine. AFAIK, the guatemalen ammo has been totally reliable in other shooters’ rifles.
I was wanting to know what may be causing the problem (weak ejector spring, a poor extractor spring, etc) and what parts I may buy to alieviate it, or if it is ammo related, although I’m not sure how ammo could cause a failure like this.
It only happened with that mag, but I don’t know if I shot enough rounds entirely to pin it on that mag alone. Would 270 total with 2 failures in that mag alone, and only with that mag, while others performed well, be enough reason to say it was that mag?
What could’ve gone wrong with that mag to cause such a failure?
I don’t know if the total rounds shot was large enough to warrent that conclusion, and nobody likes to just toss a mag…
Let’s assume for a while that its not the mag, are there any other possible causes?
Sounds like short stroking, check to make sure the gas key is tight. If it’s GTG then maybe the ammo is too weak or you’re having a gas leak at the gas block.
Would it be short stroking even if the bolt is making it far enough back and up to the point of being in the proccess of feeding the next round off the mag? The Guatamalen ammo is supposed to be m193 spec and higher velocity than the IMI .223 I’ve been using. What are the signs of a gas block leak? Carbon on the tube? How much?
The gas key is good and tight, no movement at all. However, ever since I got my LaRue rail installed the gas tube has had a wobble inside the reciever. This is not so outside the upper, it is only apperent once it is inside the reciever. Is this a possible issue? (I’ve shot ~500 since then, prior to these hiccups, after the installation with no issues)
Thanks for the responses, it feels good to be getting the kinks worked out now, for a second I though I might have another jammomatic WASR 10 on my hands:o (but thats another story;) )
Yes it can short stroke with an empty and trying to feed the next round. The easiest way to test if it’s short stroking is to load your mags with 1 round and fire. Do this 20 times if it doesn’t lock the bolt open everytime, it is short stroking.
It locked back reliably when I was shooting, probably 10-12 times (I didn’t load my mags to full capacity each time I shot) and never failed. Oh well, next time I go I’ll try that if it helps narrow it down.
If you are running a rifle spring and blue insert (std BM config) then you might try replacing them, or at leat using a cheapie o-ring next time to see if that helps. Short stroking can result from being undergassed (leaky key or tube) or being overgassed for your extractor’s and buffer spring’s power. Check out the tacked thread in the Tech Forum for a more detailed explanation.
Am I reading your reply correctly that you shot 270 rounds and the only 2 failures that you had were with one particular mag - the British steel one you mentioned?
If I’m reading that correctly - I wouldn’t even call it a short stroking problem. I’d call it a mag issue and replace it.
If you want steel mags, check out www.cproductsllc.com - for under $20 bucks you can fix the problem without it being a major issue.
It’s hard to tell what causes mag issues all of a sudden, but the sure fact is AR mags are a disposable item and should be replaced when an issue arrises. Especially when you can isolate it to a mag.
AR mags are affordable and there are plenty of good suppliers/manufacturers.
Take it out and test that questionable magazine and see if it fails compaired to a mag you know is reliable at the moment.
If it fails, save the follower, spring, and base plate for possible spares and toss the rest.
Don’t get attached to AR mags. I’ve seen plenty of “magazine attachment” cause repeat issues that are fixable with a mag replacement.
I don’t want anyone to think that I believe it’s only a mag issue - but it’s certainly a start point when it’s the only mag doing it. 16 hours around a computer has taken a toll on my though process today and I’m re-reading after a dinner break.
Over-gas could be an issue but it’s only happening with two rounds out of 270. I know that’s a low percentage and a rifle should be expected to have 0 jams out of more rounds than 270.
gotm4, I hope you don’t think I’m just dismissing your advice in my reply.
The low frequency of the jam is what is standing out.
That it just may be another issue, even possibly ammo related since it was only two rounds. It is surplus rounds - surplus for one reason or another.
I’d definitely do a mag test on that mag to start with. See if the problem becomes more consistent with that mag or in general and then compare it to another mag and see what the results are.
It’s extremely hard to help diagnose these types of issues over the internet.
My 2 cents.
(1.) Ditch that individual mag - Replace it with a USGI or HK
(2.) Clean the weapon thoroughly
(3.) Inspect the extractor - Is it worn? If so, replace it.
(4.) Install a new HD extractor spring & CRANE o-ring
(5.) Lubricate the weapon - Use at least three times what you would normally use. (Most users seriously under-lubricate)
(6.) Test fire with factory new ammo
The rifle has performed 100% for the last 2,000 rounds until the last visit. This is with all of the mags I own, the steel one included.
I could gladly call it my GOTO gun, and now my confidence is shaken. (Coincidently, I learned that I should be ready to fix jams with any weapon, all the time, no matter what. )
The only thing that has changed has been the ammo, but I’d rather not like to think of the proposition of me spending $215 on a thousand rounds of jams waiting to happen.
However, I was thinking that perhaps some of the parts may be getting old or perhaps aren’t up to handling this ammo?
Another problem is that I’d rather not waste ammo just “testing” my gun. The key is finding out what the problem is before the next time I go shooting, that way I can test the fix, instead of just trying to find a problem.
Thanks for all the replies, I wasn’t expecting so many.
I just looked up some other peoples experience with this ammo. It seems many claim the ammo is HOT. Could it be that the ammo is putting too much gas back, causing my relatively weak extractor to give way, dropping the case before it is ejected? If I had been smart enough, I should’ve saved the cases and taken a look at the rims perhaps?
One of the big questions on my mind, is why does what basically ammounts to a failure to eject, have more to do with the extractor than the ejector?
If the extractor can’t maintain a firm hold on the rim until the case mouth clears the ejection port, then the ejector will just shove the case forward into the receiver instead of the case pivoting on the extractor and going out the ejection port.
Given the evidence, should I consider ponying up the ~$40 for a sully extractor kit, or is there still a wide range of alternative problems?
I’m pretty eager to just throw some money at the problem and get some sort of solution worked out, I can’t stand having an unreliable weapon!:mad: Unfortunately, I may have to do some more testing before anything can be determined.
Here is what I was thinking,
Use only my good mags
Fire 1 round in mag for about 20 mags using Guatamalen ammo
See for failures or if the bolt doesn’t lock back.
Fire 60 rounds of IMI, see if it jams.
Fire 60 rounds of Guat. see if it jams.
Fire another 60 rounds of IMI, seeing if it jams.
Finish with 60 rounds of Guat. check if it jams.
If no failures occur, I can conclude it was more than likely that one mag, or I just got some messed up rounds.
If it fails with IMI, I know something in my rifle is going wrong.
If it fails using Guatemalen, I know something is wrong with that ammo, or my rifles ability to handle that ammo.
Lets assume for a moment that the later occurs, what improvements would be made assuming the Guatamalen is NOT underpowered, and ISN’T shortstroking (in the sense that it is too weak), but still has such jams occuring. What would be the most likely culprit at that point?
Just go to Lowes, get a pack of #60 o-rings from the plumbing section and put one around the extractor spring. Then go blast away at the range as usual.
If that seems to have fixed the problem, then you can throw money at it if you want and get the upgraded extractor spring and Crane o-ring or D-fender. Or just keep using the #60 o-rings, they last thousands of rounds for me (but I shoot strictly on 1-way ranges so I won’t get upset if I ever have one fail on me).
If that doesn’t fix the problem, then it’s likely something other than an extraction problem and you’ll have to keep troubleshooting.
)