View Full Version : Ejection Problems on Bushmaster M4
BushmasterFanBoy
10-10-06, 18:07
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.:confused:
Did it happen with any other mags during the same shooting session or since?
If it's only that mag, ditch it and replace it.
Mags are disposable and should be replaced when problematic.
Don't grow attached to an AR mag.
If it's happening with other mags, you may have cause to look elsewhere.
BushmasterFanBoy
10-10-06, 19:09
Did it happen with any other mags during the same shooting session or since?
If it's only that mag, ditch it and replace it.
Mags are disposable and should be replaced when problematic.
Don't grow attached to an AR mag.
If it's happening with other mags, you may have cause to look elsewhere.
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?:confused:
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?
Robb Jensen
10-10-06, 19:33
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.
BushmasterFanBoy
10-10-06, 20:10
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?:confused: 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;) )
Robb Jensen
10-10-06, 20:15
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.
BushmasterFanBoy
10-10-06, 21:01
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.
Any other possibilities?
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.
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?:confused:
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?
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.
My $0.02
BushmasterFanBoy
10-10-06, 22:04
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.
My $0.02
You read it correct. I had it used in my brothers carbine, no problems, but it could be a combination of that mag and my rifle. Thanks.;)
I went back and re-read all the posts again.
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.
Hard to isolate on two rounds.
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
BushmasterFanBoy
10-10-06, 23:46
I guess the problem isn't that obvious, huh?:(
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.:D )
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?:confused:
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.
BushmasterFanBoy
10-10-06, 23:54
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
What makes an extractor "worn" exactly?
Where can I get the HD spring and the O-ring from the same place?
What makes an extractor "worn" exactly?
Where can I get the HD spring and the O-ring from the same place?
If the extractor claw is damaged or worn in any way, then replace it. Look for cuts, dings, worn edges, etc.
I think several M4C dealers sell kits. I know for a fact G&R has a bolt "Upgrade" kit for sale.
BushmasterFanBoy
10-11-06, 14:43
If the extractor claw is damaged or worn in any way, then replace it. Look for cuts, dings, worn edges, etc.
I think several M4C dealers sell kits. I know for a fact G&R has a bolt "Upgrade" kit for sale.
The claw has some wear on the finish but no physical damage, or burrs.
BushmasterFanBoy
10-11-06, 15:06
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?:confused: 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?
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?:confused: 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.
BushmasterFanBoy
10-11-06, 19:01
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.
Robb Jensen
10-11-06, 19:26
I've never heard of an AR mag causing failure to eject/extract, bad mags are typically known to double-feed (2 live rounds), fail to feed. Fail to fall out of the magwell etc. After the round is out of the mag and on the bolt, the mag is out of the equation.
Your best bet would be absolutely verify that the gas block hasn't moved and if it hasn't to just replace the gas tube, gas key, extractor and ejector and springs and be done with it. (shouldn't be more than about $40 total)
This would probably cheaper than all the test firing you want to do with the different ammo.
Again with the new key have it staked with a MOACKS with new screws. Use a stronger extractor spring (i.e. Wolff XP) and/or a Crane O-ring, a new ejector and spring. I typically replace the gas tube if it looks at all worn (at the gas key end) when replacing a gas key.
BushmasterFanBoy
10-11-06, 20:30
I've never heard of an AR mag causing failure to eject/extract, bad mags are typically known to double-feed (2 live rounds), fail to feed. Fail to fall out of the magwell etc. After the round is out of the mag and on the bolt, the mag is out of the equation.
Your best bet would be absolutely verify that the gas block hasn't moved and if it hasn't to just replace the gas tube, gas key, extractor and ejector and springs and be done with it. (shouldn't be more than about $40 total)
This would probably cheaper than all the test firing you want to do with the different ammo.
Again with the new key have it staked with a MOACKS with new screws. Use a stronger extractor spring (i.e. Wolff XP) and/or a Crane O-ring, a new ejector and spring. I typically replace the gas tube if it looks at all worn (at the gas key end) when replacing a gas key.
I'm not sure if it would be necescary to replace the gas system parts would it? They all seem to be OK. :confused:
Robb Jensen
10-11-06, 20:50
I'm not sure if it would be necescary to replace the gas system parts would it? They all seem to be OK. :confused:
Maybe not, but on my fighting rifles my life is worth the $25 it costs for a gas key and tube. YMMV. ;)
If this is a play/competitiion rifle and you don't mind playing with it for possibly weeks to see what works and what doesn't, go for it test away.
Using new parts properly installed will be sure they're good. I've replaced improperly installed and not staked (factory) Bushmaster gas keys that shot loose and had less than 300 rounds total through the rifle. I've seen gas tubes damaged from as few as 3 jams where the empty casings are forced up into the upper receiver bending and damaging the end of the gas tube.
BushmasterFanBoy
10-11-06, 21:38
Maybe not, but on my fighting rifles my life is worth the $25 it costs for a gas key and tube. YMMV. ;)
If this is a play/competitiion rifle and you don't mind playing with it for possibly weeks to see what works and what doesn't, go for it test away.
Using new parts properly installed will be sure they're good. I've replaced improperly installed and not staked (factory) Bushmaster gas keys that shot loose and had less than 300 rounds total through the rifle. I've seen gas tubes damaged from as few as 3 jams where the empty casings are forced up into the upper receiver bending and damaging the end of the gas tube.
I don't think I'd be able to do the install myself. I have no way to restake the carrier and quite frankly, getting the LaRue barrel nut off has proven to be a challenge before.
Everything else is entirely feasable.
If I can't replace them, should I be OK if I check for burrs/dings on the gas tube inside the upper and make sure my key doesn't wobble?:confused:
I like to think of my rifle as being good-to go for anything, but I'm not ready to box it up and ship it out just yet.
BushmasterFanBoy
10-12-06, 08:38
Anyways, back to my major concern; is there anything I can do to the rifle assuming that it happens with only that one kind of ammo, and that ammo IS NOT underpowered?
Robb Jensen
10-12-06, 08:50
Anyways, back to my major concern; is there anything I can do to the rifle assuming that it happens with only that one kind of ammo, and that ammo IS NOT underpowered?
If it only happens with that ammo, quit shooting that ammo and see if it stops. Shoot 500 rounds of something else. I have a feeling that eventually it's going to start happening again regardless of ammo. Just a hunch feeling.
BushmasterFanBoy
10-12-06, 09:12
If it only happens with that ammo, quit shooting that ammo and see if it stops. Shoot 500 rounds of something else. I have a feeling that eventually it's going to start happening again regardless of ammo. Just a hunch feeling.
When that happens, I should follow your suggestions? Aside from putting in a new gas tube and reinstalling a carrier key, everything else is entirely possible for me. If those parts are OK (carrier staked, no wobble, gas tube isnt dinged, isn't leaking, etc.) on my rifle, then I shouldn't have to mess sending my rifle away for a few weeks, should I? Those parts really aren't a possibility for me to mess with.
I'll be going this weekend, and I'll bring some IMI to test it against. I was thinking that maybe something in my rifle is wrong, it is just being agitated moreso by the Guat than the IMI.
BushmasterFanBoy
10-14-06, 18:42
I just got back from the range. Prior to going, I put a #60 o-ring in and sprayed hoppes into the hole where the ejector spring can be seen. (I didnt have a punch)
Well.....
No problems, with any ammo, in any mags!
I had a great time shooting, as it should be!:D :D :D :D :D :D :D :D
Well, except for when I bump-fired, I had the hammer ride the BCG forward, but I figure that was just one of those things that happen with bump firing (this happened with IMI):confused:
I was shooting my rifle this weekend and had about 7 or 8 FT Ejects. Upon examination of my bolt, the ejector seemed fine with good spring tension, the extractor rim is in good shape, but dirty (shame on me), and my bolt gas rings were worn, not to the point that they wouldn't support the carrier weight if stood on the bolt face, but 2 of the 3 were obviously missing pieces/excessive gap. The carrier gas key is tightly staked down and gas tube is in good shape.
My question is could worn rings cause this FTE? I have since cleaned the rifle well and replaced the gas rings with the one piece coil type, I have also installed a new extractor spring, crane, and o ring upgrade kit just to be on the safe side. Any answers or advice appreciated.
My guess (based on previous BM experience) is that he chamber is also not 5.56 but rather .223.
1. Replace worn parts.
2. Remove the o-ring.
My guess (based on previous BM experience) is that he chamber is also not 5.56 but rather .223.
1. Replace worn parts.
2. Remove the o-ring.
My rifle has a 1:7 chrome lined heavy carbine barrel with a 5.56 NATO chamber. At the time I was shooting federal 55grn FMJ .223 ammo. I did perhaps wonder if I had too much grab on the extractor.
Magic_Salad0892
07-30-12, 23:04
My rifle has a 1:7 chrome lined heavy carbine barrel with a 5.56 NATO chamber. At the time I was shooting federal 55grn FMJ .223 ammo. I did perhaps wonder if I had too much grab on the extractor.
If it's a BM. (You didn't specify.) It could be marked 5.56mm chamber but still have a .223 chamber.
sinlessorrow
07-30-12, 23:40
If it's a BM. (You didn't specify.) It could be marked 5.56mm chamber but still have a .223 chamber.
very possible with a Bushmaster
ditch the O-ring they are very seldom needed in the M4 and alot of times not needed in the 10.5" guns either.
Magic_Salad0892
07-31-12, 00:22
very possible with a BCM.
ditch the O-ring they are very seldom needed in the M4 and alot of times not needed in the 10.5" guns either.
Not BCM.
Bushmaster. Bravo actually cares about their products.
I built the weapon from parts I got here and there. There isn't a bushmaster part in the whole weapon to my knowledge.
....a 6yr-old thread...
...that quite clearly and specifically has the word "Bushmaster" in the title....?
....when your gun isn't a Bushmaster....?
Makes perfect sense. :rolleyes:
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