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Posted: 6/4/2007 8:49:58 AM EDT
| First off, this lower is a build I did years ago. The lower is a SGW/Olympic Arms lower and I have the A-1 style stock on it. I went to clean the gun and the buffer spring came out as I popped it open. Further examination found the buffer detent in the trigger assembly and the detent spring mangled. As I looked everything over, I noticed the buffer tube just barely rides on the detent pin. I checked another AR I have and noticed the buffer tube rides over the detent a little further. But that is a collapsible stock and you can set the buffer tube where you want it. On this style, you can't. I bought this stock from a company named Quality Parts years ago. I'm just wondering what is out of spec, the tube or the receiver. Does anyone ever have any problems with an out of spec tube? Do they make a tube for the full style you can adjust like the collapsible ones? Any ideas? |
| Quality Parts Co. is Bushmaster. Sounds like somebody tried to use a front sight detent for a buffer detent.(they're similar, but the sight detent is smaller.) I saw a carbine where somebody tried this, and it was almost a mess. I would call Bushmaster or RRA and have them send me a buffer detent and spring to make sure it had the right parts in it. I may be wrong, but it may be worth a try. |
| I don't think it is the buffer detent. It looks just like the one in the other gun. It seems as if the buffer tube needs a another turn, or one more thread on the lower to hold the detent in place a little better. The tube is right on the edge of the detent. Unless the detent is out of spec, but it seems to fit in the hole just fine. I guess I could order another detent and spring, but it seems as if this tube needs to screw in one more turn to hold it into place. And I can't do that with this buffer tube. |
Great point to be made, and may be in his best interest to just have the receiver extension's stop shoulder set back to match the receiver at hand. Buying a new receiver extension to replace the old one may just end up with him in the same boat. |
| Ok, I'm mechanically challenged here. I understand what j3 is saying. I may have an out of spec buffer tube. Some are long and some are short Mine is just a little bit short. But I have no clue what Dana523 is saying. Are you saying to have the buffer tube machined to match the receiver? Makes sense, but I really don't know anyone around here that could pull that off. |
Anyone with a lathe can set back the receiver extension stop shoulder a few thousands (the stop shoulder on the tube to allow it to be threaded in the extra half turn needed into the receiver to retain the buffer retaining tube pin). You want to work the tube stop edge, and not the back of the receiver since the tube is the cheaper part. Hell, worst case you WECSOG the project if no lathe/machinist is available. |
Top right hand button of the page next to your name is a line that reads "unread messages". If you click on it, you will directed to the your IM page, and will find a IM that I sent to you on just how to WECSOG the tube stop shoulder back without a lathe. |
| Can I ask one more question? The day this happened, I my “junk” reloads were shooting as normal. The usual 3” groups. Then I ran out of them. I put my hunting loads in and they started the usual 2” group, but they immediately started printing about 4 inches to the left. Then it got worse. I went to the house and got my “precision” loads. Those were all over the map. Further inspection of the gun the next day reveled one of the gas rings was burned out. It looks more like a C-clip The bolt would almost fall out of the carrier when held upside down. At that time, I was more concerned about the buffer problem. Could all these problems been the cause of my accuracy woes? |
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Yes, inconsistencies in bolt/ammo lock up at loading and gas chamber pressurization at unlock will cause group sprayings. Regarding the mangled ring, If the destroyed gas ring was at the back end of the bolt, then check the inside of the carrier’s gas section for key channel thread burs protruding into the chamber section that may have snagged the ring. If the gas ring was at the front of the bolt (closest to the bolt face), then it could be that carrier’s reduction section just before the gas chamber section was milled a bit too far back and the front ring is escaping the parallel chamber section at unlock, Or the rings where just stacked wrongly from the start for break in. Really, the gas rings are stamp cut, and will have slight burs on the bottom sides when produced. When you go to install a new set of rings (should be free if you call up DPMS and tell them that the rifle cooked a set), take minute to debur the bottom bur’d edges of them (both inside and out with a small stone). When you go to install the new set, stack all the bottom edges (the bur’d sides you cleaned up), towards the back of the bolt (where the FP enters). The reason for this is the bottom edge is square, will seal better, and will cut carbon fouling better (on the lock up stroke) than the rounded edges on the topside until break in/they mate with the carrier’s gas chamber walls. Note: once the rings mate, all the outside edges will be square, but you can still tell the stacking direction by looking at the inside edges for orientation. This comes in handy for say, after you have done a detailed stripping/cleaning of the bolt with the rings removed. |
| Well, I have a legal M-16 also. I put this upper on the AR a couple of months ago. This bolt assembly is a spare out of the 16, though it has several thousand rounds on it. I headspaced it with the guages I have and it checked out fine. At the time, I decided to leave the other bolt and carrier with the other upper since they were broken in together. That's an AR carrier in that upper. I've decided that since this is a new upper, I'll buy a new bolt just for it and let those two wear in together. Not sure yet which carrier I'll use. It was the back gas ring that let go. Happened once before years ago with the M-16. Extractor broke and when I took it apart to fix it, I noticed one of the gas rings was broken. I can't remember which one was bad. Didn't know anything about deburring the rings though. I just remember that last one was a pain to get on. I've also ordered a new buffer tube. I'm curious to see if there is a difference between the two. I'll use your method to fix the old one anyway. Jeeze, over the years I've accumulated enough spare parts that I could almost build another if I picked up a spare lower. Thanks again. Can't wait to get this gun running again so I can find a decent load for it. |
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Mod the old tube to work with the receiver as stated (to retain the buffer retaining pin when installed/tightened). As for the receiver being out of spec, watch for signs of buffer face damage like in the below photo (#1 type damage), and get back to us if you start to see such appearing. 
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Chances are the back of the receiver is just a bit thicker overall at the threaded section for the receiver extension, and the reason that you had to mod the stop collar on the tube to make it work (retain the buffer retaining pin). If the problem is that the buffer retaining pin detent channel is milled to far forward in the receiver instead, the back of the carrier is will not push the buffer back away from the retaining pin at upper/lower lock up, and the end result would be the buffer face tagging the pin at each lock up stroke during live fire (#1 in the photo). And if anyone was wondering, #2 is burs on the back of the carrier (inside and out), with #3 being a burr on the bottom of the carrier U channel that is scrapping down the buffer face as the upper/lower is locked up. And to point out, the buffer in question was junk to begin with (read not anodized correctly, if even at all), but makes for a great photo to use for reference. |
| Eureka. A friend told me of a machine shop within 12 miles of me. He machined the buffer tube so now everything is just peachy. For a measly 6 bucks. Old 'Nam vet, so he was familiar with the gun. He too said the receiver was not milled enough at the back as the pin was not battered. I'll get this gun together but it will be a few days before I can test it. Hopefully with the new bolt, the accuracy will come back. |
| It may have made a gap between the but plate and the end of the tube if you milled it to sit shorter by screwing further in. I would make sure that the stock screw was not going to pull the but plate down because of the gap and crack it now. Some of the old plates are more brittle than the new ones. |
| Never thought of that. Since I can't see in there, gotta hope for the best. I also thought I had an A-1 stock. Went to put it together and the spacer fell out. Now I realize I have an A-2. Been over 14 years since I put this lower together. Guess my memory is shot. |
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