AR-15 Vibration/Clunk After Each Shot

Dirt Merchant

Dirt Merchant

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I am getting an unexplainable vibration/clunk after every shot (except the last shot in the mag) I take with my AR-15 that I recently assembled (Rainer Arms lower with Vltor upper). I have made sure everything is tight that should be tight and even swapped out the Milspec buffer for a JP Enterprises Free-floating Spring (which got rid of the vibration) but there is still a perceptible clunk. I have a Noveske that shoots fine and a my friend's Danial Defence MK18 shoots fine as well. The only thing left that I have noticed is that there is a little wiggle between the upper and the lower on my AR-15 but my friend's DD MK18 has the same amount of wiggle. I have ordered an Accu wedge to see if that makes any difference. Any suggestions would be appreciated.

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I assume you meant to say "unexplainable." At what point do you get this "clunk"?

Does it shoot well? Functions correctly?

Might as well jam a used earplug in there rather than waste money on an accuwedge.
 
No easy way but to do process of elimination. Do you see any unusual or premature wear in the internals?
 
It's magazine spring vibration that is transmitted to your ear muffs when it touches the stock. The clunk are the rounds hitting the bolt carrier after a round is stripped from the magazine.
 
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OP mentioned he installed a "JP Enterprises Free-floating Spring" which I'm going to assume is the JP Captured Silent Spring.

If you do happen to have the JP Captured Spring system installed... Did you remove the buffer retaining pin when you installed the JP Captured spring system? When you screwed the buffer back on, did you leave the buffer tube extension just shy of the retaining pin hole on the lower or did you replace it back to the half-way mark? Does the buffer extend just slightly into the receiver?

Some buffer tubes are slightly longer than others and there may be extra wiggle room between the buffer and your bolt carrier and this may be what's causing the "clunk" sound. You can try shimming the JP system by inserting a quarter into the buffer tube before inserting the JP system.
 
Stevo said:
I assume you meant to say "unexplainable." At what point do you get this "clunk"?

Does it shoot well? Functions correctly?

Might as well jam a used earplug in there rather than waste money on an accuwedge.
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Dam... sorry about that. UNexplainable vibration/clunk. The rifle shoots fine and functions correctly. It feels like the clunk happens when the bolt moves forward and picks up a new round but I am pretty new to rifles so I can't really say exactly when it happens. Its before the trigger resets.
 
Trinimon said:
OP mentioned he installed a "JP Enterprises Free-floating Spring" which I'm going to assume is the JP Captured Silent Spring.

If you do happen to have the JP Captured Spring system installed... Did you remove the buffer retaining pin when you installed the JP Captured spring system? When you screwed the buffer back on, did you leave the buffer tube extension just shy of the retaining pin hole on the lower or did you replace it back to the half-way mark? Does the buffer extend just slightly into the receiver?

Some buffer tubes are slightly longer than others and there may be extra wiggle room between the buffer and your bolt carrier and this may be what's causing the "clunk" sound. You can try shimming the JP system by inserting a quarter into the buffer tube before inserting the JP system.
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I have the JP Enterprises Silent Captured Recoil Buffer Spring installed which seems to have gotten rid of the "twang" sound. I removed the retaining pin and shimmed the JP Buffer Spring with a quarter as suggested but I still hear the clunk. The bolt looks like its butted up against the end of the buffer when I close the upper. I am wondering if it could have something to do with the trigger (I have taken it out and put it back in) as I have limited AR experience and I don't hear the "clunk" sound when shooting a Noveske with a TriggerTech trigger or a Daniel Defence MK18 with a Geissele trigger. It may be my OCD kicking in as other people have shot my rifle and say its fine. My friend who owns the DD MK18 says he feels "something" as well.
 
The "clunk and vibration" is from the buffer and buffer spring as it slams another round into the chamber, it is just the nature of the beast. you can just ignore it or fine tune it with different buffer and spring weights until you don't feel it anymore.
 
hbean said:
The "clunk and vibration" is from the buffer and buffer spring as it slams another round into the chamber, it is just the nature of the beast. you can just ignore it or fine tune it with different buffer and spring weights until you don't feel it anymore.
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I could live with that answer if the Noveske and DD MK18 I have shot made the same or similar sound, but they don't. That is the puzzling part. I looked all over the buffer tube and can't see any name brand on it. I assume its milspec as I have a Magpul ACS stock on it but does that mean its crap if I can't find any manufacturing stamp on it?
 
Dirt Merchant said:
I could live with that answer if the Noveske and DD MK18 I have shot made the same or similar sound, but they don't. That is the puzzling part. I looked all over the buffer tube and can't see any name brand on it. I assume its milspec as I have a Magpul ACS stock on it but does that mean its crap if I can't find any manufacturing stamp on it?
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Some ARs make the "clunk...boing" while others don't. I think it is caused by minor binding of the spring and buffer within the extension tube. Try putting a crap load of grease in the extension. This has worked for me.
 
Dirt Merchant said:
I could live with that answer if the Noveske and DD MK18 I have shot made the same or similar sound, but they don't. That is the puzzling part. I looked all over the buffer tube and can't see any name brand on it. I assume its milspec as I have a Magpul ACS stock on it but does that mean its crap if I can't find any manufacturing stamp on it?
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Not necessarily, but the interior finish could be not as good as say DD or novekse.
 
Dirt Merchant said:
I could live with that answer if the Noveske and DD MK18 I have shot made the same or similar sound, but they don't. That is the puzzling part. I looked all over the buffer tube and can't see any name brand on it. I assume its milspec as I have a Magpul ACS stock on it but does that mean its crap if I can't find any manufacturing stamp on it?
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DD and Noveske took their time in select the right balance of buffer weigh and spring rate to work with their BCG, I am going to guess that you didn't really thought much about that when you start putting parts together for your build.
 
hbean said:
DD and Noveske took their time in select the right balance of buffer weigh and spring rate to work with their BCG, I am going to guess that you didn't really thought much about that when you start putting parts together for your build.
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Well... being new to AR-15s, I did some research to figure out which parts I wanted in my first build but I am not at the level of Noveske or DD at picking spring rates to match BCGs. I did recently learn about adjustable gas blocks but the shells ejects straight out of the bolt so it seems balanced. I did not realise there was such a difference in weight in BCGs. I have a BCM BCG in my AR and I have tried the BCG from the Noveske AR in my AR but I still felt the same "clunk".
 
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