New AR Build - BCG Getting Stuck in Rear Position

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allivak

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Hello,
Just finished up my first AR build....finally got everything I needed and did a thorough pre-cleaning and lube before putting it together. I slide the BCG in behind the charging handle and everything appears fine as it goes in nice and smooth. However, upon charging it for the first time, the BCG keeps getting stuck in the rear-most position at the back. I was perplexed especially after 15-20 seconds had passed when the BCG suddenly slammed home by itself, almost gave me a heart attack lol. the problem persists despite checking for any snags in the upper and despite the BCG sliding freely inside the upper without the lower receiver in place.

maybe 1 in 10 times it will function as it should, the other 90% of the time I charge it up, the BCG gets stuck and my charging handle goes limp.....I can usually free it up by tapping/pounding pretty hard on the stock and it will slam home.

I pulled out the BCG and I don't see any signs of wear either. i'm very new to ARs but I'm going to assume it has something to do with the buffer assembly? gun hasn't been fired yet, I've heard of BCG/CHs that aren't very smooth at first but never heard of this issue. Quick google search was of no help.

Any ideas?

Thanks
 
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Check the buffer tube retention pin that sticks up out of the lower in front of the buffer tube. If the tube isn't threaded in far enough, that pin will either fly out or occasionally stick up too far then snag the carrier. Seen it happen once, and the rifle reacted exactly as you described.
 
thank you sir for the quick reply. your suggestion seems right....

however, are there any tricks or tips for installing the buffer tube assembly correctly so as to avoid this issue in the first place? I really took my time when I was assembling this AR because its my first build...I'm very confident that I installed it correctly the first time....so if there are any secret ninja tips, it would be greatly appreciated. ;)

Thanks!
 
I had a similar problem on my 458 SOCOM build. The BCG hangs up and if I hit it it will fly forward. I'm pretty sure mine was caused by a faulty buffer tube. If I put the upper on another lower, it works just fine. I think the buffer tube was either out of spec, or slightly bent, or something. I originally thought it was binding on the upper, but eventually narrowed it down to the buffer tube itself.
 
There really isn't much that can go wrong installing the buffer tube. You just turn it till it hits the detent and stops you, then tighten the castle nut. Something else I would check is your bolt catch...
 
I agree, I am not sure how I could of improperly installed the buffer tube....but I'll re-do it and make sure its tightened until it stops. i don't think it can be the bolt catch, but I'll check that as well.

thanks guys, very helpful stuff
 
so yeah....i just double checked the buffer tube and there is essentially nothing I can do....the end plate will only line up once every couple turns on the threads and there is only one place that I can get everything to line and properly hold the detent down. if i crank it any further, it won't complete a full rotation because its up against the detent as far as it can go and nothing lines up. yet if i back it out any further the detent is no longer retained within the receiver. :(

any idea on what about this could be causing the issue? it appears to be properly installed so I'm not sure what is wrong. could the detent just be too tall?
 
Where did you get your receiver extension (buffer tube) from? Sounds to me like either it, or the threads in the lower are out of spec. It's almost always the Receiver Extension with these symptoms.

I assume since it's your first build, you don't have spare parts lying around to try out. You can take a flashlight and shine it down the extension after removing the buffer and spring. You should be able to see some marks on the inside where the bolt carrier is hanging up.

You mentioned the buffer retainer. If you look at the very top of it, or in the slot on the bottom of the bolt carrier you'll see wear if that's where it's hanging up. But that's rare, as they can usually be pushed beyond flush with the receiver extension to get the buffer in and out. So the bolt carrier just pushes it down.
 
You're not really supposed to "lube" the buffer and spring. Clean with CLP, then wipe dry.
 
Blade First said:
"You're not really supposed to "lube" the buffer and spring. Clean with CLP, then wipe dry." -- dogmush

Nonsense. Lubing makes for better and quieter operation.
Click to expand...
I'm just going by the TM.

Nothing in there needs lube, it's just something else to get dust in.
 
If the detent is held to the proper height( like it is on yours from your description) sharpie the bolt carrier and cycle it to see where it gets worn. If it isn't touching anywhere pull the upper off and push the buffer back in the tube to see if IT hangs up. Usually this is a bent buffer tube if the detent is OK, and maybe find a buddy with another ar to try out his upper on your lower. Kinda hard to know for sure without holding the gun, but hopefully this advice can help you track down your problem. Btw, if you lube the spring/buffer, use a light grease or really light oil and go sparingly. Too much will slow down the carrier and track dirt all over inside your rifle. And I say that from experience, a little may be good but a lot is bad in an ar15. My .02
 
Quality, all Anderson components in the lower/buffer...although I'm not sure why that is even relevant at this point(unless of course, you are trying to prove how much better your favorite expensive brand is...)
 
adcoch1 said:
If the detent is held to the proper height( like it is on yours from your description) sharpie the bolt carrier and cycle it to see where it gets worn. If it isn't touching anywhere pull the upper off and push the buffer back in the tube to see if IT hangs up. Usually this is a bent buffer tube if the detent is OK, and maybe find a buddy with another ar to try out his upper on your lower. Kinda hard to know for sure without holding the gun, but hopefully this advice can help you track down your problem. Btw, if you lube the spring/buffer, use a light grease or really light oil and go sparingly. Too much will slow down the carrier and track dirt all over inside your rifle. And I say that from experience, a little may be good but a lot is bad in an ar15. My .02
Click to expand...
thanks for the help, I'll check the tube out closer and let you guys know what I find.

when I re-installed the buffer assembly last night....I did push down on the buffer to make sure the spring wasn't the problem or to see if it was binding up without the BCG installed....but all seemed fine and there were no snags or hang ups.
 
although I'm not sure why that is even relevant at this point
Click to expand...


Tolerance stacking is the reason. Your upper could be out of spec? your BCG? etc. etc. etc.

What I choose isnt even relevant to the conversation.
 
well at this point, I think its safe to say something is out of spec...but I'm still unsure how this could be helpful in fixing the problem.

BTW, i didn't mean to come across so snippy....I just see a lot of "brand elitism" on gun forums and I sort of assumed that was where you were going with your post. I apologize if that was not your intention.
 
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but I'm still unsure how this could be helpful in fixing the problem.
Click to expand...


Really??? all anyone here can do is launch guesses at you over the internet.
You have been offered a couple of things to look for. Aside from that you need to have someone experienced look at it. Good luck.....
 
Try taking the spring and buffer out and clean the spring and buffer thoroughly. Reassemble. Then take a dowel or similar object and cycle the buffer back and forth several times slowly to see where it.binds. Then just manually cycle it with the dowel about 50 or more times to see if it polishes out. I suspect that it will.
 
well at this point, I think its safe to say something is out of spec...but I'm still unsure how this could be helpful in fixing the problem.
Click to expand...
What? If something is out of spec, figuring out what that is and fixing/replacing it is the only way to fix the problem. Seems like it might possibly be helpful to identify it.
 
dogmush said:
"You're not really supposed to "lube" the buffer and spring. Clean with CLP, then wipe dry"

To each their own but they are moving parts. Mine get lubed. The lube also helps to keep the "spriong" noise to a minimum.
kwg
 
allivak said:
Quality, all Anderson components in the lower/buffer...although I'm not sure why that is even relevant at this point(unless of course, you are trying to prove how much better your favorite expensive brand is...)
Click to expand...

Anderson is one of the cheapest out there, yes?
 
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