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AR-15 BCG Getting Stuck in Buffer Tube

Malfunction BCG Buffer Tube Stuck friction

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#1 OFFLINE   tacticool510

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Posted Jun. 30 2018 - 03:14 PM

Whats up guys

 

So I just picked up my AR from the gun store after getting a cerekote done on the upper and lower receiver.

I also purchased a Sharps Rifle Company XPB Bolt Carrier Group and Radian Raptor charging handle.

Upon installing those parts, the rifle has became very difficult to charge. The BCG will get stuck half way through the buffer tube and sometimes all the way in the buffer tube.

So I tried to lube it up but its still very rough and feels like there is a lot of friction going on. 

I took out the XPB BCG and put my original BCG back in and it runs smooth after that.

Its an American Tactical upper and an 80% built lower. All metal, no polymer. 

I was thinking maybe getting a new buffer tube assembly(new tube, spring, and buffer) because its pretty old and the buffer shows signs of a lot of wear. 

Im not close to being a gunsmith so I need some help from the more experienced guys here. 

I haven't tried to run any rounds through it with the XPB because i'm just too worried I might damage something. 

 

 

 




#2 OFFLINE   ScoutnUSA

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Posted Jun. 30 2018 - 03:33 PM

Can you tell where it's sticking? Any unusual rub/wear marks?

Anything different in the design between the two bolts?

Can yo mic the bolts?

Any burrs?

You could "paint" the both bolts with a magic marker and see if there are different points of contact?

Does the new bolt cycle by hand ok.

If you pull the buffer out does the new bolt slide freely in and out?

 

Darrell


Edited by ScoutnUSA, Jun. 30 2018 - 03:48 PM.



#3 OFFLINE   tacticool510

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Posted Jun. 30 2018 - 03:44 PM

I noticed some carbon was building up around the gas key but most of the rubbing is happening at the rear of the bolt carrier. 

It's strange because the XPB BCG is designed to have less friction than any other BCG.(thats what they advertise)

When I insert the XPB BCG it does feel really rough. However with the standard BCG, its smooth with no issues. 

I also forgot to mention when I insert the charging handle it also feels rough when its moving freely. 

I haven't tried to pull the buffer out, I was only looking at the exposed side of it(where the BCG pushes it in).

Im at work so I will have to try that out tonight. 




#4 OFFLINE   tacticool510

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Posted Jun. 30 2018 - 03:46 PM

Im not sure how to post pictures on here but the bolt on the XPB has tapered lugs. Where as the standard bolt is not tapered. 




#5 OFFLINE   ScoutnUSA

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Posted Jun. 30 2018 - 03:51 PM

Have you tried the new bolt with the old CH?

Tried the old bolt with the new CH?

Is the gas key getting jammed in the CH?

Bent CH?

 

Darrell




#6 OFFLINE   tacticool510

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Posted Jun. 30 2018 - 03:55 PM

Havent tried new bolt and old CH

Old bolt and new CH works great

Gas key has no issues with CH.

Both new and old CH look fine.

..and I just now remembered testing out the XPB BCG in my buddys AR and it was cycling fine. 

 

EDIT: Im an AR-15 noob, im not sure what you mean by "mic the bolts" and "burr"


Edited by tacticool510, Jun. 30 2018 - 04:08 PM.



#7 OFFLINE   towtruck

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Posted Jun. 30 2018 - 04:11 PM

Sounds like a tolerance issue between all the new parts. I would be swapping things like mentioned above and see where the problem lies. Look for signs of rubbing that will be a tell tell.




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#8 OFFLINE   tacticool510

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Posted Jun. 30 2018 - 04:29 PM

Will defiantly have to start swapping things around tonight. Thanks for the help guys.

I will keep you guys updated on my progress. 




#9 ONLINE   Retcop

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Posted Jun. 30 2018 - 06:45 PM

Will defiantly have to start swapping things around tonight. Thanks for the help guys.

I will keep you guys updated on my progress. 

 

Good luck and welcome to the board !

The more info you can provide the better these guys can help you.

You have come to the right place.

 

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#10 OFFLINE   porterdavid98

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Posted Jul. 01 2018 - 09:31 AM

Did I lose something trying to understand this post? Are you thinking the Cerokote has or has not changed the fit in the interior dimensions? I have done powder coat and that was a problem but not with Cerokote.


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#11 OFFLINE   towtruck

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Posted Jul. 01 2018 - 11:50 AM

Did I lose something trying to understand this post? Are you thinking the Cerokote has or has not changed the fit in the interior dimensions? I have done powder coat and that was a problem but not with Cerokote.


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Yea, you got lost.........the gun works fine with the old BCG and coatings applied according to his post....it's the new BCG that is having issues. 




#12 OFFLINE   tacticool510

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Posted Jul. 01 2018 - 06:32 PM

Sorry if I didn't make it clear. I wanted to state everything I've done to the rifle just in case if someone else had the same issue.

 

So I started swapping out different parts. 

With the old charging handle and new BCG, it is a little bit easier to charge but it still gets stuck in the rear position. 

Im starting to notice more when I do it, a lot of carbon build up gets on the rear of the BCG, but nothing much else on the rest of it. 

 

I dont have any magic marker to see where the contact points are but i'm going to try and get some soon. 

 

When I insert and remove the BCG while the rifle is separated, it feels buttery smooth. Its just when it goes into the buffer tube, it gets tight and stuck.

I was thinking about getting a whole new buffer, buffer spring, and buffer tube. 

 

EDIT: Will putting lube in the buffer tube hurt at all? 


Edited by tacticool510, Jul. 01 2018 - 06:40 PM.



#13 OFFLINE   towtruck

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Posted Jul. 01 2018 - 06:54 PM

Sorry if I didn't make it clear. I wanted to state everything I've done to the rifle just in case if someone else had the same issue.

 

So I started swapping out different parts. 

With the old charging handle and new BCG, it is a little bit easier to charge but it still gets stuck in the rear position. 

Im starting to notice more when I do it, a lot of carbon build up gets on the rear of the BCG, but nothing much else on the rest of it. 

 

I dont have any magic marker to see where the contact points are but i'm going to try and get some soon. 

 

When I insert and remove the BCG while the rifle is separated, it feels buttery smooth. Its just when it goes into the buffer tube, it gets tight and stuck.

I was thinking about getting a whole new buffer, buffer spring, and buffer tube. 

 

EDIT: Will putting lube in the buffer tube hurt at all? 

I use white grease on my buffer spring and buffer. Oil is fine too. 

 

Have you tried your upper and new BCG and charge handle on a completely different lower?.........I would be checking all those parts on a different lower. Once you have tried that and it all works well you can figure out which part of your lower is the culprit. And, if it won't work with another lower you know the issues are in the parts of the upper somewhere.

 

I'm not knocking your 80% lower but that is the first part that comes to mind for being out of spec. It's the nature of the beast.




#14 OFFLINE   R3DNECK91

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Posted Jul. 01 2018 - 06:56 PM

Try taking the buffer and spring out and by hand insert both bcg in a ways. Look if theres anything the new bcg is catching on. If theres nothing put the buffer and spring back in. If you can get a good grip on the bcg and try to push the bcg in with spring and buffer installed.
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#15 OFFLINE   tacticool510

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Posted Jul. 01 2018 - 07:08 PM

Cool, will definitely try out those methods. Thanks for the help again guys. 




#16 OFFLINE   hzhardy

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Posted Jul. 02 2018 - 12:21 AM

Some carriers have “skis” on the rear portion to prevent carrier tilt when used in a gas piston application. What thjs means is the tail is slightily oversized. With that in mind, I have seen all kinds of f’d up stuff with cheaper buffer tubes. I have had them look like the inside was carved out by a cave man and some that were not bored deep enough for the carrier to go back enough. With that said you can use some of your ladies lip stick on the carrier to see where it is catching. Also look at the gas key area.


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#17 ONLINE   Retcop

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Posted Jul. 02 2018 - 05:11 AM

How far does the BCG normally move into the buffer spring tube when the bolt is 

cycled through discharging a round ?

Ball park anyway since I realise it's going to differ with the stiffness of the spring

the buffer weight, and the energy of the round fired.

I'm just curious...thabks.




#18 OFFLINE   MadeInUSA

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Posted Jul. 05 2018 - 02:57 PM

Im wondering if the Cerakote on the lips of the upper and lower have something to do with it. Hold the rifle up to a light and try to look between the upper and lower.


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#19 OFFLINE   bamashooter

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Posted Jul. 05 2018 - 08:23 PM

How far does the BCG normally move into the buffer spring tube when the bolt is 

cycled through discharging a round ?

Ball park anyway since I realise it's going to differ with the stiffness of the spring

the buffer weight, and the energy of the round fired.

I'm just curious...thabks.

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#20 ONLINE   Retcop

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Posted Jul. 09 2018 - 05:44 AM

The audio is optional: 

Thanks Bama !

Does not get any better than that !


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Also tagged with one or more of these keywords: Malfunction, BCG, Buffer Tube, Stuck, friction

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