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Posted: 2/24/2007 9:21:53 AM EDT
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Hello I recently purchased a lightly used AR15 and I have had some problems with it failing to lock back on an empty mag (75% of the time) and failures to feed(1 in 10 fired). The fist thing I did was try some c-product 20 round mags instead of the 30 the came with the rifle. Next I tried several different kind of ammo( Black Hills white box, Ultramax, and American Eagle) it did not matter, I still got the same results. So I read the troubleshooting checklist. I don't have a caliper so I could not check some things, and since this is my first AR I don't know what normal/easily are in this weapon. I also forgot to bring a hex wrench to check the screws on the bolt carrier. Well more to the point I notice that my buffer had several nicks in it from the buffer retaining pin. Since I was supposed to be looking for this I am wondering what kind of malfunction this will cause and if it is related to my other problems. If it could cause problems then I assume that I would need to get a new bolt buffer but what can I do to correct the cause of those dents? Wow that took a long time for me to get out. I hope someone can understand that. Oh and I forgot I have to store my firearms in the armory on base, so I do not have access to them right now. It takes an hour to check them out, so even though I know pictures would probably help, but I forgot to bring my camera the last time I went out.
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As for the buffer damage, really need a photo to advice you of the next step there, but chances are the back of the carrier at the bottom C slot has a protruding bur that is doing some dinning on the buffer face. Get back to us on if the key Allen bolts are correctly tightened (35 in lbs). And you did fully clean (chamber brush used) and CLP lube the rifle before it’s maiden voyage? |
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No, I pretty much did everything wrong when I bought this rifle. I figured I could clean it like in basic and treat it like my mosin nagants where armorer's tools = large rock. Boy was I wrong. I will get back with pictures of the buffer tube, and I will use my calibrated elbow to tighten the screws, but they looked like they were staked in. I know that I have some more to do to get it running right. The main thing was I thought I may have found a possible problem, and due to my location I have to order parts online. So my chamber brush should be here this week and I will have to clean it out, and then test it. Testing may have to wait as I will probably have to work this weekend. I found some pics I took right after I bought it. They don't look like they will help but they can't hurt. http://farm1.static.flickr.com/128/404299935_56b8c497ce.jpg?v=0 http://farm1.static.flickr.com/174/404299931_2e66db6f46.jpg?v=0 http://farm1.static.flickr.com/187/404299946_905403beaf.jpg?v=0 http://farm1.static.flickr.com/132/404299955_d6b53745df.jpg?v=0 http://farm1.static.flickr.com/126/404299967_5495e3490d.jpg?v=0 Tell me if there is anything else you would like to see pics of besides the buffer and the area around it. |
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My guess is too much grease (or dirt) in the buffer tube. Both FTF and failure to lock open can be caused by impediment of the buffer spring. Some people grease their buffer springs and over time the grease becomes gunk due to age or dirt build-up. Pull the buffer spring and buffer from the buffer tube. Clean out the inside of buffer tube, clean off the coils of the buffer spring, and clean off the buffer. Lightly lube or grease the buffer spring and replace. ETA: The damage to the buffer may also be due in part to a sticking buffer spring if the buffer is slapping around rather than riding behind your carrier. Note that most buffers get an outer ring of use, which is not necessarily damage per se. So pics of the buffer face would be helpful. |
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Take the accuwedge out and post a pic. of the buffer retaining pin hole. Had an Armalite with the hole in the wrong place relative to the buffer extension. When you close the upper and lower together w/ the BCG in place, does the bolt carrier push the buffer into the receiver ext. about 1/16-1/8 of an inch to relieve the pressure from the buffer off of the buffer retaining pin? LMK INCIRLIK |
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Well I took it out yesterday, and after a though cleaning of the chamber it seems to run better while sitting. It still hiccups every once in a while while standing. http://farm1.static.flickr.com/132/417095778_e353e9e966_b.jpg What size are the gas key screws, because none of my allen wrenches would work. http://farm1.static.flickr.com/163/417095780_15ca443ce7_b.jpg http://farm1.static.flickr.com/182/417736016_94b25bae5b.jpg http://farm1.static.flickr.com/145/417736004_acc5a3996e.jpg On an unrelated note my take down pins are really hard to install and remove, read hammer. When the upper is removed they slide in and out easily, so I don't think that it is the detent spring. With the upper in place it gets hard. Is something out of alignment, or am I worrying too much? |
Do you mean that you cleaned the inside of the buffer tube and cleaned off the buffer spring? If you did and it improved alot, I think a new high quality buffer spring will fix your standing problem. You will not be able to back out the hex bolts because they are staked in pretty good. Because they appear to be sufficiently staked in, I do not think they are the problem. |
| I cleaned the tube and the spring, but they were not that dirty. I think what really helped was cleaning the chamber. If you think the spring could be the problem what would you recommend for a "high quality" spring. Also is it possible to put the buffer spring on backwards? It did not look like it, but it is never good to make assumptions when troubleshooting. |
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edited since the receiver's buffer retaining pin channel has been cracked and the epoxy was used to cobble the pin side wall back together, along with a bad bedding job. Short of rewelding the buffer retaining pin channel, and redrilling/reanodizing it, the receiver is toast unless you just want to use the receiver without the pin. |
I bought it from Old Sacramento arms in California, so they ground off the bayonet lug and I don't know what the set screw is for. I do know that it is tight, and that it is shooting where I aim. Ok I see how a previous owner tried to bed the action. Is there any other way to remove the crap from my AR other than a blowtorch. I am hesitant to go to those measures. |
Dremel tool. You gotta love amateur gunsmiths.  Seriously, but very lightly and very slow. You can smooth out that receiver and remove the JB. |
| Good advice above on how to unFUBAR your lower. Once all else is done, if you still have cycling issues, you should check the alignment of the front sight base and the gas port... those sight bases that are held in place with a set screw are not always the most secure, especially if you have the GI plastic handguards. Any misalignment between the gas port and the FSB will risk gas loss and consequential cycling problems. |
It's pretty dicked up obviously, take it to someone who knows ARs and just get it fixed right. Shooting to point of aim doesnt mean the gas block is properly aligned with the gas port on the barrel either.  I see a useable bolt carrier group and furniture, not much more. Any chance of sending this rifle back for a refund? You could build or buy a much better rifle. I wonder if that's bedding or a repair of some cracking or breakage on the receiver. |
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The bedding job may be holding the carrier just off of the buffer so that the carrier does not mate up against the buffer when the upper and lower are mated. Thus, the buffer gets beat up against the buffer retaining pin at the very end of travel because the back of the carrier is not stopping the buffer but rather the buffer retaining pin stops the buffer. Please do not dremel. Call the people who sold it to you and explain to them that you are dissatisfied with the home gunsmith special and the problems it has. No one would expect a used AR15 to be a JB Weld up. I am sure that they did not advertise it as a JB weld special. In other words, try to return the gun or at least get an adjustment on the sale. If they do not, I for one will be happy send them a "I think you are an a&&h0LE" letter with regard to the situation. If they do not take it back, I recommend that you get a new rifle buffer spring and 3 new gas rings from Midway to get the rifle going. The buffer face thing is unsightly and assembly/disassembly is pain but I think I tryin to fix, if possible since it is all down in the receiver, is too much trouble. Just get the gun shootin and chalk up the rest to experience. Trust me, we all have stories to tell in that arena. |
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Sorry, just came off an S&W rifle post and thought that this rifle was a S&W factory built rifle, just used with bedding alone. The rifle needs to go back to the seller for a refunds!!! After a closer look, the epoxy was used for bedding, and to repair the buffer extension pin channel as well. As for the FSB having a bottom screws, best guess is that the barrel FSB was installed canted on the barrel, and there fix may have misaligned the FSB gas channel with the barrel gas port. If you have the tools, then with a new lower receiver and maybe if you correct the barrel/FSB without having to replace the barrel, your still over the $100 mark. Worse case, the receiver and the barrel needs to be replaced, and if you add in smithing cost, you over the $400 mark. |
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A pic of the upper http://farm1.static.flickr.com/59/417736025_0f27e09fa0.jpg FSB http://farm1.static.flickr.com/159/417989870_5e9287d12d.jpg I see how to take off a good FSB with this thread in the build your own forum. Do I just unscrew the set screw to remove mine, and how do I ensure that it is aligned properly? This thread poses the question, but it does not have any answers yet. As too returning it I don't think that is an option because I had a 3 day period to send it back and I have blown that by 2 months. I don't really mind using a hammer to assemble it , although it would be nice not to have to. More important to me is getting it so it does not malfunction, although I understand they may be related. I suppose I could try and sell it and cut my losses, but that would not be fair to the next guy. I should have known better than to buy cheap, I just hope that this was not a $600 mistake. |
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To pull the FSB, loosen the bottom setscrew and it should slip straight forward. Do not twist the FSB side to side or you will bend the gas tube. If needed, heat the FSB up with a torch to break any locktite if it was used, and you may still need to use a rubber or leather mallet to slip the FSB forward off the barrel. With the FSB off the rifle, post a photo of the barrel rounds under the FSB location. I would like to see if the barrel has old FSB taper pin slots, or even side flats for side set screws. As for the barrel gas port, it needs to be top dead center of the upper receiver line, and you may have to pull the CMP hand guard system to reindex the barrel correctly. So, not only a photo of the side of the barrel at the FSB rounds, but a shot of the top of the barrel looking backwards down the gas port to upper receiver line as well. As for how to reinstall the FSB (still pending if the current FSB single screw is the best option), with the barrel gas port at least close to TDC of the upper receiver, you mark the barrel shoulder at the center of the gas port, then use the indexed mark against the gas tube. Again, the barrel gas port has to be close to TDC or when you adjust the FSB to zero out the rifle, you may block the barrel gas port with the FSB twisted too far alignment of the two for the needed zero. |
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I would not mess with the FSB until you have done all of the easy things first. The easiest thing to do now is the buffer spring. ETA If the spring is 12 inches or less, it is at least part of the problem. Have you done the gas ring check? 1. Remove carrier/bolt assembly. 2. Remove cotter pin, firing pin and cam. 3. Push bolt halfway into bolt. 4. Hold carrier upside down and see if bolt slides out of carrier. If bolt slides out, you need new gas rings. Gas rings are easy to replace. Another easy thing to do is to shoot non-chlorinated brake cleaner down the gas tube to clean it out. Some of the earlier Radway stuff would clog up rifle length gas tubes. I still recommend calling the original seller and complaining. I would even point to this thread. I would at least ask for a partial refund. Explain that your in the service and have restrictions on you for checking out the rifle. The worse thing they can say is no because they can. I am bored at the moment. I am thinking about clicking on their ads and asking "Does the weapon have a screwed-up JB weld bedding job like other rifles you typically sell?" |
| I have done a gas ring check according to the troubleshooting checklist, and it passed. In fact it had what seemed like more than plenty resistance, like I said I don't really know what normal is with this rifle. I have to go back to the armory Monday morning, because they would not let me keep more than 1000 rounds of ammo in there. I will measure the recoil spring, but will probably leave the FSB alone. I am not an expert, but if it works while sitting (providing a more steady recoil platform) and not while standing then I think it would have more to do with the moving parts of the rifle. The FSB could still be inhibiting gas, but that is in addition to another problem. |
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Again, the best option is to send it back. You definitely have a gas problem. With the other dicked up home gunsmithing it has there's no way I'd trust that the FSB is properly aligned. Maybe even somebody knowledgeable in working on the uppers would let you send it to them for a bit of work and not charge an arm and leg. You can mail the upper to anyone, it's not an FFL part. As far as the lower, you might consider not even using the buffer retainer. It makes disassembly/reassembly easier but you can get by without it. You'll just have to use both pushpins and be careful. |
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This is a minor thing but if you wish to remove epoxy or JB weld, find a well ventilated place and use a pencil type soldering gun. The heat will loosen/burn the epoxy off the metal and you will be able to scrape it off. This may be more benign to the receiver than the Dremel. Do not breathe the fumes. I agree with the earlier poster to remove the bedding to see what you have first and then decide whether you wish to proceed with any further action on this firearm. |
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Well I measured the recoil spring today, and it measured 13 inches, so that is not the problem. I talked to the TSgt at the armory on base, and he said whenever they have problems with the front sight, or gas port being clogged they replace the entire barrel assembly. He also said that it was not possible to remove the FSB with out expensive specialized tools on USAF weapons. So my next step is tearing the gun down getting rid of the jb weld. Then I will check the alignment of my FSB, and clean it if necessary. But that won't be until next week probably. |
WTF????? I see one bottom setscrew and no taper pins. Barring them have welded/brazed the FSB on to the barrel, a simple torch should all that is needed to break any loctite bond (if used) after loosening up the sets screw. |
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ziebart, You have someone's old rifle used for high power competition. It is common to bed the lower receiver to fit the upper. It is also common to use a set screw front sight instead of the standard taper pin one. The gas port could also be sized to only work with a specific "heavy" load. I'm guessing the rifle was sold after the barrel was shot to the point of accuracy loss. Best thing you can do at this point is to pull off the front sight to check the gas port alignment and size and remove the bedding compound to see if that allows the carrier to hold the buffer off the detent. |
| Well I went out again today, and after removing the epoxy/ JB weld from the lower it ran fine. There was a lot of that junk on there, and I am sure that it was impeding the movement of the bolt carrier or something. It took several hours, using a dremel with a wire wheel and a knife to scrape it off, but it is off now. I want to thank everyone for their help in resolving this matter. Now the only thing left to do is replace the safety selector detent spring, as mine rotates through all three positions easily. |
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Ziebart, It sounds like you may have an M-16 selector. Scroll down here. www.ar15.com/content/legal/AR15-M16Parts/ |
| Naw I thought the same about the selector, and then tried to pull the trigger while in the 3rd position. The hammer did not fall, and acted like another safety position. Not only that it does not look like the one on the guide you posted. Thanks for looking out though. |
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