While studying my AR15 I saw what was happening.On my rifle, When the action is closed, there was daylight between the buffer and the bolt carrier. When the action is closing the back end of the bolt carrier must push the buffer back 1/16 of an inch so that the buffer won't bang on the detente pin when the action is cycling. To prove my theory I looked at my brothers Bushmaster which functions flawlessly and does not have a single ding in the buffer. Sure enough, when I slowly closed the action, i watched the bolt carrier engage the buffer and push it about 1/16" away from the detente pin. Voila! I guess I need an extended bolt carrier.
found why my buffer is all dinged up
- Thread starter His
- Start date
- Status
Taurus 617 CCW
Member
An AR-15 will function properly if the bolt carrier group pushes the buffer rearward slightly when almost closed. This pushes the buffer off the buffer retainer.
BBBBill
Member
His said:
Good luck with that. I've never seen one in over 40 years of fooling with these things in the Army and as a civilian owner. Better to do a full examination of your parts against the blueprint specs to see what is off. It may not be the bolt carrier at fault. It may not be one thing at fault, but rather several that are not correct.
WestKentucky
Member
Im interested in seeing some pics if you can get any. I know it's a tough spot to get a real good look at, but I'm curious to see what's happening...or in this case isn't happening.
Taurus 617 CCW
Member
I have seen this issue on some lowers that had the buffer retainer hole drilled too far back on the lower receiver. As far as I know an extended BCG doesn't exist. This is because it needs to clear the lower receiver buffer tube thread hole (the loopy thing that holds your buffer tube to your lower). If you had an extended carrier it would hit the top of the threaded hole and you wouldn't be able to close the gun fully. What brand of lower is it? Is it a complete rifle or a kit build?
Do you really want to trash your lower receiver? You can save your "out of spec" lower. I've done this to 2 different guns that had this problem with zero malfunctions or drawbacks of any kind. Just find somebody with a lathe and chuck your buffer in it. The buffer is the most expendable (cheapest) piece of this equation. Some may scoff at this but I challenge them to try it before they dismiss it as BS. See attached.
Attachments
col.lemat
Member
That will work. Did one that I had years ago the same way. The lower was out of spec (non Colt) and this is the only inexpensive option.
Quentin
Member
Screwing the buffer tube in one more turn might work. Or testing another buffer tube.
Edit:
Sorry, ignore... I was thinking of a different issue. Modding the buffer like mtrmn said sounds like a good fix.
Edit:
Sorry, ignore... I was thinking of a different issue. Modding the buffer like mtrmn said sounds like a good fix.
Last edited:
badkarmamib
Member
The buffer tube would not have anything to do with the pin/buffer relationship. Never saw the idea of turning the buffer face in a lathe before, great idea. Either a) the detent hole is drilled in the wrong location, or b) the upper is pinned too far forward on the lower. Mine is of the b) persuasion, but not quite as bad as yours. Good luck with whatever solution you decide on.
The upper is RRA, the lower is an AR57 out of Kent Washington. It was put together by a fellow here in town who is reputed to be a gunsmith. When I showed him the busted off detente pin and battered buffer he replaced the pin and told me not to worry about it. The rifle has only 100 rounds through it. I guess he expects me to take a bag of pins when I go to the range. I then went to another smith here in town. I could tell he didn't know what was wrong by the silly things he said. He asked if the rifle functioned ok and I said yes. He too said not to worry about it, shearing a pin occasionally wouldn't hurt anything. I have left the piece with another smith in another city. I was not able to talk with him. He is supposed to call me when he can tell me what it will take to fix it. While I was driving home, I figured out what was happening. When I got home I checked out my brother's AR and yes, I was right. When I closed the action I saw the rear of the carrier push the buffer back about 1/16". When I close the action on my rifle the carrier does not contact the buffer. I will look up the milling of the buffer solution and I will post when I get a fix.
I've messed with enough of these things that I've had 3 of them with this problem---all builds of various mfg. I did lots of things trying to fix it while everything I read said "I wouldn't have that out-of-spec POS! Throw it away and get a REAL lower." But I just was NOT going to trash an otherwise perfectly good lower.
I even welded some extra metal on the end of a carrier and filed it down flat. THAT WORKED and the extended carrier is still in service without problems. Then it dawned on me that I still was not thinking correctly about the relationship of the lower/upper/carrier/buffer. That's when I took the least expensive of those parts and came up with this solution. I'm sure some folks like col.lemat above had thought of this before me, but I had no knowledge of it at the time. ETA: The simplest solution is usually the best solution IME. This was so simple I was kicking myself for not thinking of it sooner.
I have been otherwise occupied for over a year and have not really had time to browse the forums, but that situation has improved immensely. I'm glad I could be of help to someone on my first visit back. And so sorry to hear of RC's demise...He was so full of knowledge.
I even welded some extra metal on the end of a carrier and filed it down flat. THAT WORKED and the extended carrier is still in service without problems. Then it dawned on me that I still was not thinking correctly about the relationship of the lower/upper/carrier/buffer. That's when I took the least expensive of those parts and came up with this solution. I'm sure some folks like col.lemat above had thought of this before me, but I had no knowledge of it at the time. ETA: The simplest solution is usually the best solution IME. This was so simple I was kicking myself for not thinking of it sooner.
I have been otherwise occupied for over a year and have not really had time to browse the forums, but that situation has improved immensely. I'm glad I could be of help to someone on my first visit back. And so sorry to hear of RC's demise...He was so full of knowledge.
Last edited:
Elkins45
Member
Turning a shelf onto the buffer is ingenious. If a fellow didn't have access to machine tools he could almost do that with a grinder or Dremel if he took his time and marked everything well.
carbine85
Member
How about just cutting a notch in the tube and thread it in one more turn?
Your lower isn't the problem it's your upper. I went through this several times with the retaining pins just marring the living crap outta the buffers. You guys are completely correct, when the upper mates with the lower I needs to push the buffer back ever so slightly.
You need to true / lap the face of your upper receiver.
Once I did that the problem completely went away on every affected rifle. Brownells makes a tool specifically for that. http://www.brownells.com/gunsmith-t...15-lapping-tool-sku080000182-20220-44377.aspx
Sent from my iPhone using Tapatalk
EDIT:
I feel like I should add that you should only true the receiver face only AFTER having double and triple checked that everything else is in spec. I.E. Buffer retaining pin location and BCG.
Might be helpful for me to add that on one rifle even after truing and lapping the receiver face I was still getting ever so slight dings in the face of the buffer.
To solve this I disassembled, and used one of my DMT bench stones to take off a few hundredths from the receiver face. I'm sure a steady hand and a fine file would work just as good. Don't forget to true it up again. Wrap the threads in masking tape to protect them during the process.
What we're doing here is seating the barrel ever so slightly further into the upper which in turn pushes the BCG further in and that results in the BCG making proper contact with the buffer when you mate the upper to the lower.
Last edited:
If you are very careful, yes you could do this without a lathe. You just have to make sure you leave enough raised surface area for the bolt carrier to push against. If you go much deeper into the diameter than .120" you may cause the buffer to to fall into the inner dia of the bolt carrier. If you compare the rear end of the bolt carrier and the face of the buffer, you are losing a lot of the necessary contact surface when you make that cut. You only want to clear the tip of the retainer pin and NO MORE.
If there is a machine shop near you, it may be prudent to pay someone to do this for you. Around here I know the machinists and they're all into guns themselves. I'm sure they would do it free of charge if I asked, especially after showing them the problem and the fix.
Last edited:
All this would do is compress the buffer spring more and possibly limit the rearward travel of the buffer during operation. Not to mention other headaches of re-machining the end of the tube to accomodate the buffer retainer.
The goal is to bring the rear of the carrier and the front face of the buffer closer together when the gun is fully assembled. As has already been stated, the carrier should contact the buffer AND PUSH IT BACKWARDS A SLIGHT AMOUNT when the action is closed and pinned. The buffer should NEVER contact the retainer pin until the action is opened for maintenance.
You are 100% spot on my good Sir. All OP needs to do is get the Brownells receiver lapping tool, some lapping compound and boom problem solved.
Sent from my iPhone using Tapatalk
Be it known to all who read this: I am NOT disagreeing with the above post. Indeed it has caused me to re-think my own position because it had not occurred to me to seat the barrel deeper other than to make sure the barrel nut was tight.
I agree with what you're saying- especially AFTER you added the edit--this would work as well. In 1 of my guns, there was a visible gap between the buffer and bolt carrier. I never thought of your idea before I came up with the buffer shelf cut. In that 1 case I probably would have had to seat the barrel a LOT deeper, like .020" or so, in order to break contact with the buffer retainer.
I don't have an accurate enough way to measure the pin hole locations compared to the buffer retainer location, but through a process of elimination you can reasonably determine where the problem lies. Remember, the pin holes in the UPPER can be off as well.
Pinning another KNOWN GOOD upper (borrow one from a buddy?) on the lower will help diagnose all these problems. If the problem remains after pinning a known good upper assy on the problem lower, then you know the problem lies within the lower. In that case you would be better off using my method. It's also a lot cheaper, easier and you can undo it by simply installing a new buffer.
If the problem goes away when you swap uppers then the problem is likely in the original upper. Therefore, seating the bbl deeper on the original upper would likely be the ticket.
ETA: Until now I had considered the lapping tool to be something that the most anal target shooter would use. I am now taking another look at this as well and will probably be ordering one soon. Thank you Band1dth for pointing this out.
Last edited:
While I was diagnosing the problem I came across this PDF that shows the exact location that the buffer retaining pin is suppose to be. I'll include a link. http://bit.ly/2bP8ppu
Sent from my iPhone using Tapatalk
I'm sorry we may have over-complicated this problem and the solution for you HIS. Swapping uppers to see where a problem lies is a good basic troubleshooting exercise and many of us gun folks are mechanically inclined enough that we LIKE doing this stuff.
By all means, at least swap a good upper to see what's going on. Even put your upper on his Bushmaster lower to see if it works to solve the problem. Let us know what you find!! Keep in mind that WHATEVER your findings may be, cutting the step on the buffer face WILL work. Regardless of what the gun actually needs. This is cheaper/easier and will make the problem gun work as designed as long as it functions well otherwise. Do not exceed the dimensions on my pdf. You may get away with just taking .020" or .030" off instead of the .040".
If you do decide the upper assembly is at fault, and you want to tackle disassembly of the upper receiver, you will need several special tools to remove the barrel from the upper receiver without damaging your weapon. Tearing into this may be right down your alley and if you do it you will be learning a lot about HOW and WHY an AR works - or doesn't work. The way I got into this was by building most of mine from parts kits myself. Then troubleshooting problems:banghead: that usually stemmed from my purchase of the absolute CHEAPEST parts kits I could find. But when you learn the hard way, it is an educational experience you won't soon forget.
I don't know your level of experience, technical ability, or your access to a good work area with basics like a vise/workbench. Therefore I suggest first going to Brownells.com and or youtube and watching some of the ar15 assembly videos, concentrating on upper assemblies/barrel replacement.
I just went to Brownells.com, clicked on "learn" and found a total 246 videos and articles about AR15's and at least 1 vid about the lapping tool previously mentioned. Probably 95%+ of them will not be dealing with full disassembly of the upper, but educational nonetheless.
By all means, at least swap a good upper to see what's going on. Even put your upper on his Bushmaster lower to see if it works to solve the problem. Let us know what you find!! Keep in mind that WHATEVER your findings may be, cutting the step on the buffer face WILL work. Regardless of what the gun actually needs. This is cheaper/easier and will make the problem gun work as designed as long as it functions well otherwise. Do not exceed the dimensions on my pdf. You may get away with just taking .020" or .030" off instead of the .040".
If you do decide the upper assembly is at fault, and you want to tackle disassembly of the upper receiver, you will need several special tools to remove the barrel from the upper receiver without damaging your weapon. Tearing into this may be right down your alley and if you do it you will be learning a lot about HOW and WHY an AR works - or doesn't work. The way I got into this was by building most of mine from parts kits myself. Then troubleshooting problems:banghead: that usually stemmed from my purchase of the absolute CHEAPEST parts kits I could find. But when you learn the hard way, it is an educational experience you won't soon forget.
I don't know your level of experience, technical ability, or your access to a good work area with basics like a vise/workbench. Therefore I suggest first going to Brownells.com and or youtube and watching some of the ar15 assembly videos, concentrating on upper assemblies/barrel replacement.
I just went to Brownells.com, clicked on "learn" and found a total 246 videos and articles about AR15's and at least 1 vid about the lapping tool previously mentioned. Probably 95%+ of them will not be dealing with full disassembly of the upper, but educational nonetheless.
- Status
