AR Chewing Up Buffer!

S

SwampYankee

New member
I've got a Stag lower attached to a YHM upper and a DD barrel. I went to clean it and noticed that the buffer tube was all chewed up and plastic flakes were all over the inside of the lower. Any ideas what is causing this, I've never seen it in any of my other AR's.
 

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I would check the back of the BCG. It may have some burrs on it for the manuf. process. Or you may just have a crappy buffer but either can be replaced.
 
I've seen that on buffers before. Looking at the pattern it looks like it is slamming the buffer into the buffer retaining pin hard enough to cause some chips out of the buffer. By any chance are you running an upgraded action spring? Checking the back of the BCG seems like a good idea also.

Either way, I've seen buffers that looked much worse which remained perfectly functional. In the one case I had, I ended up switching out the buffer and the problem went away, so it may also be some factor in the buffer construction.
 
Where did the "plastic flakes" come from? Is the bumper intact on the other end of the buffer? Looks like something has been gnawing on the sides of the lower near the threads. What's with that?
 
Looking at pix,my theory was wrong.,maybe.If you went to an A-1 stock and used an A-2 buttstock screw,you might beak up the plastic bumber on the end of the buffer.So,its a collapsable stock...agreed,its not the A-2 screw

While plastic is softer than the face of the buffer,the bits will flatten,but they are not compressable.Contamination between the faces of the BCG/buffer might very well make an impression in the buffer.Steel mold faces get impressions from plastic bits on the parting lines .
 
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Here is a maybe.There is an A-1 butstock,and an A-2 buttstock.The A-2 is about 5/8 in longer.The same buffer tube is used with both.A spacer is used with the A-2 buttstock
Click to expand...

Good thinking, but this is a collapsible stock, so there's no A1/A2 differences.

I think Bart is on the right track... it's looking mostly like it's impacting the retaining pin, but there could also be a burr on the back of the carrier.

If the gun functions, it may not be an issue (so long as it doesn't break the buffer retaining pin). You could try a heavier buffer and see if that cuts down on things a bit, but I don't know that it would be necessary.
 
The OP picture is of a collapsible stock. But you're right about the A2 buttplate screw tearing up the buffer.
I end up with a bunch of unrelated loose AR parts on hand and recently discovered a couple of carbine buffers that would not allow full bolt travel with certain springs in one of the elcheapo collapsible stock buffer tubes I had laying around. There was just enough difference that the bolt would not retract enough to lock back.
OP
Double check to make sure there isn't something stuck in the back end of the buffer tube.
 
That is an unusual amount of wear on the face of your buffer. I would check the back of you bolt carrier group for rough edges and smooth them out if any. If you could attach a picture of your bolt carrier that would help as well. If your rubber bump at the back of your buffer is chewed up at all I would replace either my tube and/or buffer spring as one of them is the likely culprit. I think the plastic (likely Al alloy) chips were from the face of your buffer.
 
Dumb question, but is your buffer tube staked correctly? looks like to me there is a possibility that your tube may be loose. maybe its just my eyes going crooked this late at night, but the tube doesnt seem to be in a straight line from the centerline of the barrel. I had an issue similar to this when i installed my 6 position stock, didnt get the castle nut to the correct torque and staked. had nightmares fixing that one.... Double check your buffer weight. Any problems with short stroking? Possibly over gassing issue, though ive never seen a buffer face torn up from over gassing, usually just the buffer pad on the back of the buffer... I know, lots of questions leading opposite ways, but im lost as to what could be causing this if your buffer tube is staked correctly and straight.
 
That type of buffer face damage is caused by either the buffer contacting the buffer retainer pin or by a rough surface or burr on the back of the BCG.

Run a stone across the back of the BC and break the edges very lightly.

Can you turn the RE one more turn?

When you close the upper onto the lower does the BCG contact the buffer just as the upper is in the closed position? When pinned together the BCG holds the buffer back from the retainer pin.

The buffer retainer pin hole in the lower could be out of spec. Not a uncommon problem.

Plastic flakes??? Remove the buffer and inspect the back of it, is the nylon stop damaged?
 
Yes, I personally staked the castle nut and it is tight as can be. No wiggle at all.

The "plastic" does appear to be chips of aluminum off the buffer.

It does appear that the buffer is slamming into the retainer pin.

I used the Tapco spring when I attached the Tapco collapsible stock. I assume it is a standard weight spring.

So how do I solve this problem? If the lower is out-of-spec I could send it back to Stag. But how do I know what the spec is? The bolt carrier is smooth as a baby's bottom. When I drop the lower, it appears that the BCG pushes on the buffer but if the YHM upper is out of spec, could that be the problem? I thought the YHM parts were supposed to be of high quality but the more I read, the less impressed I am. Sigh. I hate to buy a new upper to find out it was the lower....
 
interesting...i would start small.

See if replacing the spring will help, it could be that you spring is returning the buffing into the retaining pin awfull hard. This can also be caused by having a light buffer, they are made in different weights...research (not likely but worth a shot)

If that route produces more Al off the buffer then try replacing your bolt carrier (not your bolt and firing pin) with something more substantial...like say one from Patriot Ordnance Factory in the m16 Design. Its added metal along the bottom may protect your buffer better, hard to tell from the pictures what design you have.

If that dosent work replace the buffer, it could just be a bad batch of buffer that you got and its unusualy soft on its face.

Your parts could be out of tolerance in one area or another but that is hard to say from pictures. I have no way of telling you exactly what the solution will be as I do not have the weapon in front of me. I would start with the above suggestions and with the cheapest replacement first. That way if its fixed from the cheap one you havent spent much money already. It is most likely not your upper and the only part I can think of as being out of tolerance would be your buffer retaining pin hole may be set back to far not allowing the bolt to stop the buffer from hitting it during normal operation. Its rare but mixing reciever brands can cause some slight takedown pin issues and this may be the cause as well. Dozens of possible solutions start small. Hope this helps. Jeez I keep thinking of more...your bolt carrier could be short and drawing your buffer out of the tube more because of that allowing your buffer to slam into you retaining pin...out.
 
I had marks like that once on a bushmaster. Taking the burs off the back of the bolt carrier and swapping in a new buffer made the problem go away.
 
It does appear that the buffer is slamming into the retainer pin.
Click to expand...

The bolt carrier is smooth as a baby's bottom. When I drop the lower, it appears that the BCG pushes on the buffer
Click to expand...

The bolt should move the buffer back about .060 or more when the upper is pinned. If the bolt is moving the buffer back then it can't be fitting the retainer pin. Odd circumstances.

Is it possible this wear was caused by a burr on the bolt that is now worn off? Do you have another buffer you could use and see if it is marked when fired?

Could there been any fod on the back of the bolt? Piece of primer?:confused:
 
Order a good quality buffer and spring from Brownells. If the retainer is beat up, order a new one of those,too. While waiting for those to arrive, disassemble the buffer tube from the lower and swab it out thoroughly to make sure there isn't something jammed in the recess. This is the least expensive starting place and worth the cost to know your buffer system is in good condition.
I can assure you the lower cost collapsible stocks don't use the highest grade buffers/springs.
 
On your YHM upper.
There are some folks who write on forums.I do not know if they are being paid by the "elite" brands,(its cheaper than buying advertising)or whether they just get some ego trip out of it.They live to trash any brand that is not on their "cool" list.
I have built with YHM uppers,lowers,and forends.All were great products at value prices.Without hesitation I wouuld build with YHM again.I place more stock in my own experience than what I read.
The part functional relationships,I just do not see where the upper figures into your problem.
I think I would look at the Tapco products first on the order of "suspect"
When you pull the takedown pin,and hinge open your rifle,the BCG should be flush with the rear of the upper,and the buffer should protrude from the receiver extension(buffer tube) by roughly something just over 1/16 in..

When you close it up,the buffer is pushed back by that 1/16 in,off the buffer retainer,In operation,the buffer should make no contact with the buffer retainer,

When you hinge open the rifle,is the BCG flush with the rear face of the upper,or is it sunk in deeper? If it is flush,the upper assy,including BCG is as it should be.

When the buffer is stopped by the buffer retainer,does the buffer protrude 1/16+,so it must be forced to the rear by the bcg when you close the rifle?If so,then I do not see how contact could occur..If the hole in the lower,that holds the retainer,is drilled off location,then the buffer will not protrude sufficiently.
Even with a new buffer,nothing behind the flat front face really matters.

If the bcg is sub flush(sunk deeper into the upper than level) there is a problem.

I don't have time to take down a rifle and study close,but would the cam pin /bolt/bcg relatinship be what stops fwd travel?What can be very bad is a broken cam pin.The bolt does not rotate to lock up,but the rifle fires.
 
I looked at your pic again.See those parallel scratches that radiate out from center?HMMM.Retainer cannot do that.Look at your BCG,at 6 oclock,see the "keyway" looking slot? There are some kind off burrs there.Use a hard,fine stone,like an India.Dress off any high spots .Then make a small,about three thousandths,corner break the sharp edges.
 
I just realized, I have 2 BCG's. One is a RRA and the other is a Delton. I'm not sure which is in there now but I was swapping in a CMMG .22 conversion and I may have put the 2nd BCG back into this rifle (I've check the BCG that is in it now and cannot find any burrs). I'll check the first BCG which is the one that has been in the rifle when all the damage happened. Hopefully that is the cause.

I was shopping buffers and springs to replace my current ones, does anyone have an insight on the Spikes heavy buffers?
 
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