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Posted: 12/7/2008 11:36:21 AM EST
~700 rounds through this gun. midlength upper, carbine buffer, standard spring (M4 6-position stock).
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Posted: 12/7/2008 11:43:07 AM EST
[#1]
That must have been fun to get open.
How does your bolt carrier look at the rear? |
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Posted: 12/7/2008 11:47:21 AM EST
[#2]
Manufacture?
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Posted: 12/7/2008 12:02:06 PM EST
[#3]
Quoted:
That must have been fun to get open. How does your bolt carrier look at the rear? The carrier looks perfectly fine. Might be a little wear right below the firing pin I store the gun with the bolt locked back, could that have contributed to the problem? It looks like the retainer sheared off. |
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Posted: 12/7/2008 12:13:26 PM EST
[#4]
It looks like either the groov on the bottom, rear of the carrier isn't deep enough or the firing pin shroud has been rubbing it. It sounds like the firing pin area. That means that your carrier has been going too far back in the buffer tube.
FWIW my DPMS regular carbine buffers are a slight bit longer than my Bushmaster "H" carbine buffer. The rubber piece is larger. If it is a parts gun you may have found the unlucky combo of parts. Try a new spring and DPMS buffer. |
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Posted: 12/7/2008 12:49:08 PM EST
[#5]
Did you assemble the lower yourself? Which parts kit did you use?
If you purchased the lower, who manufactured it? ETA: Spell check. |
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Posted: 12/7/2008 1:04:10 PM EST
[#6]
It looks like a DPMS lower with a notched non-DPMS hammer. RRA or Stag lower parts kit? Who made the buffer and bolt carrier?
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Posted: 12/7/2008 1:12:09 PM EST
[#7]
What does the buffer look like?
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Posted: 12/7/2008 1:17:08 PM EST
[#8]
As a weapon is pivoted closed, the back of the bolt carrier should make contact with the buffer face, pushing the buffer to the rear, relieving the spring tension applied on the buffer retainer.
During firing, the buffer should not come into contact with the buffer retainer. Most likely your buffer WAS making contact with the buffer retainer, causing the buffer retainer to shear off. |
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Posted: 12/7/2008 1:24:58 PM EST
[#9]
Quoted:
As a weapon is pivoted closed, the back of the bolt carrier should make contact with the buffer face, pushing the buffer to the rear, relieving the spring tension applied on the buffer retainer. During firing, the buffer should not come into contact with the buffer retainer. Most likely your buffer WAS making contact with the buffer retainer, causing the buffer retainer to shear off. What would cause that / what is the fix? With my lower apart from the upper, the buffer was touching the retainer. |
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Posted: 12/7/2008 1:26:02 PM EST
[#10]
DPMS lower, RBPrecision LPK, assembled myself
Buffer tube/buffer/spring was bought on the EE, unknown make (sold by TheTic00) |
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Posted: 12/7/2008 1:30:54 PM EST
[#11]
Quoted:
With my lower apart from the upper, the buffer was touching the retainer. In that condition it should. When you pivot the weapon closed, it should not. If the buffer does touch the retainer when the weapon is closed, most likely the buffer retainer pocket was drilled incorrectly in the lower receiver. |
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Posted: 12/7/2008 1:50:00 PM EST
[#12]
Some of them do that. I think the metal is soft. I have had it happen on 3 factory built DPMS lowers. After I replaced the retainer it never happened again.
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Posted: 12/7/2008 1:52:28 PM EST
[#13]
Show us a picture of the buffer face, and bottom of the bolt carrier group and you will probably have a definate answer. If the face of the buffer is beat to hell I agree with the poster avove and think that the bolt carrier is too short or the detent hole is drilled into the receiver too far back.
If the bottom of the bolt carrier has a thin wear mark on it near the firing pin shroud, I think that would do it quicker than the buffer. The bolt carrier is definately harder than a buffer face. I would figure the face of the buffer would be destroyed before that detent pin. |
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Posted: 12/7/2008 1:57:53 PM EST
[#14]
I will also do that if you fire or work the bolt on the rifle without a buffer assembly installed.
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Posted: 12/8/2008 4:33:09 AM EST
[#15]
Quoted:
Show us a picture of the buffer face, and bottom of the bolt carrier group and you will probably have a definate answer. If the face of the buffer is beat to hell I agree with the poster avove and think that the bolt carrier is too short or the detent hole is drilled into the receiver too far back. If the bottom of the bolt carrier has a thin wear mark on it near the firing pin shroud, I think that would do it quicker than the buffer. The bolt carrier is definately harder than a buffer face. I would figure the face of the buffer would be destroyed before that detent pin. I will take some pictures when I get home. The face of the buffer has some small nicks in it, but they don't really seem to be significant. The firing pin shroud also has a little wear on it, but I can't figure out if it's normal wear or not. It's smooth instead of pitted like I would expect if it slammed into that retainer. Aside from replacing the retainer, are there any parts I absolutely should replace? If the carrier is going too far back, should I get a heavier buffer? |
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Posted: 12/8/2008 5:03:16 AM EST
[#16]
Geez...I'm not sure what to think... It looks like te BCG sheared it but if it looks fine I'm at a loss. I'll be very interested to see what those here smarter than I think caused this.
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Posted: 12/8/2008 4:00:34 PM EST
[#17]
The carrier seems fine. You can see wear on the pin shroud.. is that normal? It's smooth, not like it was banging anything hard. The buffer, though.. you can see 2 big pits near the top of the picture here, and the outside face right next two those two bits is really worn down and scratched up. Do the outer edges of buffers normally get wear? It's either rubbing the bottom of the buffer tube or it was hitting that buffer retainer and then running over it. 
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Posted: 12/8/2008 5:42:50 PM EST
[#18]
carrier too short? retainer hole to far forward?
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Posted: 12/8/2008 6:10:53 PM EST
[#19]
Quoted:
I will also do that if you fire or work the bolt on the rifle without a buffer assembly installed. WTF are you talking about here??? |
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Posted: 12/8/2008 6:15:07 PM EST
[#20]
Quoted:
http://jake.tnmccoys.com/misc/guns/carrier1.jpg The carrier seems fine. You can see wear on the pin shroud.. is that normal? It's smooth, not like it was banging anything hard. The buffer, though.. you can see 2 big pits near the top of the picture here, and the outside face right next two those two bits is really worn down and scratched up. Do the outer edges of buffers normally get wear? It's either rubbing the bottom of the buffer tube or it was hitting that buffer retainer and then running over it. http://jake.tnmccoys.com/misc/guns/buffer.jpg Can you show a picture of the bottom side of the carrier at the extreme back surface. Also the rear surface that touches the buffer and also the narrow slot at the bottom rear of the carrier that is supposed to ride over the detent during carrier cycling. Something is making contact with that buffer detent to break it off or wear it down like that. |
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Posted: 12/8/2008 7:03:56 PM EST
[#21]
Quoted:
I will also do that if you fire or work the bolt on the rifle without a buffer assembly installed. This is it. Or did you use a carbine buffer with a rifle tube? |
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Posted: 12/8/2008 7:24:35 PM EST
[#22]
Quoted:
Quoted:
I will also do that if you fire or work the bolt on the rifle without a buffer assembly installed. This is it. Or did you use a carbine buffer with a rifle tube? Why would someone work the bolt without a buffer in it? And if the buffer tube/receiver extension is removed then the buffer retainer comes out. Also What would having the wrong buffer have to do with this. Something is rubbing the retainer. Is the retainer hole not drilled deep enough? |
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Posted: 12/8/2008 9:25:45 PM EST
[#23]
The wear on the bolt carrier below the firing pin is probably from contacting the hammer face in order to cock the hammer during the carrier's rearward travel. I don't see a problem there.
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Posted: 12/8/2008 10:01:45 PM EST
[#24]
Quoted:
Quoted:
I will also do that if you fire or work the bolt on the rifle without a buffer assembly installed. WTF are you talking about here??? Nice response. Why don't you think about it before using the keyboard? |
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Posted: 12/8/2008 10:01:52 PM EST
[#25]
Quoted:
Quoted:
Quoted:
I will also do that if you fire or work the bolt on the rifle without a buffer assembly installed. This is it. Or did you use a carbine buffer with a rifle tube? Why would someone work the bolt without a buffer in it? And if the buffer tube/receiver extension is removed then the buffer retainer comes out. Also What would having the wrong buffer have to do with this. Something is rubbing the retainer. Is the retainer hole not drilled deep enough? When I was in the service occasionally someone would field strip their M16 and forget to but the buffer and spring back in. When you pull the charging handle the bolt carrier travels farther back than it is supposed to and hits the retainer pin with the area that normally shrouds the firing pin. This often shears the retainer pin immediately or soon after. I have seen it at least a dozen times. Even if it happened sometime later the very first question the armored would ask was "Did you ever forget to reinstall the buffer assembly and charge the weapon?" |
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Posted: 12/9/2008 2:48:43 AM EST
[#26]
Quoted:
As a weapon is pivoted closed, the back of the bolt carrier should make contact with the buffer face, pushing the buffer to the rear, relieving the spring tension applied on the buffer retainer. During firing, the buffer should not come into contact with the buffer retainer. Most likely your buffer WAS making contact with the buffer retainer, causing the buffer retainer to shear off. +1...right on the nose |
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Posted: 12/9/2008 4:26:50 AM EST
[#27]
Quoted:
Quoted:
http://jake.tnmccoys.com/misc/guns/carrier1.jpg The carrier seems fine. You can see wear on the pin shroud.. is that normal? It's smooth, not like it was banging anything hard. The buffer, though.. you can see 2 big pits near the top of the picture here, and the outside face right next two those two bits is really worn down and scratched up. Do the outer edges of buffers normally get wear? It's either rubbing the bottom of the buffer tube or it was hitting that buffer retainer and then running over it. http://jake.tnmccoys.com/misc/guns/buffer.jpg Can you show a picture of the bottom side of the carrier at the extreme back surface. Also the rear surface that touches the buffer and also the narrow slot at the bottom rear of the carrier that is supposed to ride over the detent during carrier cycling. Something is making contact with that buffer detent to break it off or wear it down like that. I'll take pictures. I can tell you that I looked the bottom rear of the carrier over very closely and it looks pristine next to that slot. I don't think the slot was hitting the retainer, it seems to me like the buffer itself was hitting it. I've never fired/worked on my gun without the buffer/spring in it. It's a carbine buffer, spring, and tube. |
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Posted: 12/9/2008 5:39:58 AM EST
[#28]
btw, RB Precision is sending me a new retainer for free, even though I bought the LPK from them over a year ago.
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Posted: 12/9/2008 8:33:33 AM EST
[#29]
Quoted:
Quoted:
Quoted:
I will also do that if you fire or work the bolt on the rifle without a buffer assembly installed. This is it. Or did you use a carbine buffer with a rifle tube? Why would someone work the bolt without a buffer in it? And if the buffer tube/receiver extension is removed then the buffer retainer comes out. Also What would having the wrong buffer have to do with this. Something is rubbing the retainer. Is the retainer hole not drilled deep enough? I don't know... ask the dozen or so privates I've seen do it.  That's when you're really grateful for the forward assist.
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Posted: 12/10/2008 5:32:36 PM EST
[#30]
I measured my buffer and spring and the dimensions are within spec (3.25" on the buffer and 11" on the spring). |
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Posted: 12/11/2008 6:14:20 AM EST
[#31]
should I run the gun with the new retainer and same buffer/spring and just monitor for wear?
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Posted: 12/11/2008 10:03:42 PM EST
[#32]
Like Quib was saying, as you close the the upper and lower together, with the front pivot pin pushed in and pivoting the upper down to close with the lower, check that the carrier makes contact with the buffer pushing it away from the retaining pin.
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Posted: 12/12/2008 1:58:17 AM EST
[#33]
Quoted:
should I run the gun with the new retainer and same buffer/spring and just monitor for wear? I don't think you have any other choice at this point. Replace the retainer, perform the Buffer to Carrier contact check like I originally suggested, shoot the rifle, and monitor the retainer. |
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Posted: 12/12/2008 4:27:57 AM EST
[#34]
Quoted:
Quoted:
should I run the gun with the new retainer and same buffer/spring and just monitor for wear? I don't think you have any other choice at this point. Replace the retainer, perform the Buffer to Carrier contact check like I originally suggested, shoot the rifle, and monitor the retainer. I will do that. So if they do come into contact, I'm good to go.. if they don't..? |
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Posted: 12/12/2008 6:28:17 AM EST
[#35]
Let us know the problem when you get it solved.
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Posted: 12/12/2008 7:41:35 PM EST
[#36]
Could this also happen if the action was cycled without a barrel installed or if the bolt is travelling too far forward when locking into battery? Without anything to stop the bolt, the BCG will continue to travel forward making the buffer slam into the retainer pin.
The same thing just happened to me, and I was cycling the action with the barrel not installed because I'm waiting on other parts before I assemble the upper. I was function checking the charging handle and bolt carrier group after putting them together, and when I opened the upper back up again, the buffer tube came out and the top of the retaining pin rolled out onto the table. I am assuming that when I released the charging handle, the bolt flew forward and, having nothing to stop it up at the barrel end, the buffer just kept going and slammed into the retainer pin. If that's the case the I learned a lesson not to cycle the action without a barrel installed, but if something else is going on I need to figure it out. |
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