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Posted: 4/15/2007 9:30:31 AM EDT
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From reading other threads in this forum, I believe it is time to open a thread for this issue. Because I am a relative newbie to AR troubleshooting, this issue may take some time to correct. Please avoid the temptation to bash this rifle, or to repeat tired urban legends regarding this rifle, I have heard all of them already, have compared them with statements from Bushmaster staff, and personal opinion, my own, and those gathered from extensive research, and this will not help resolve the issue(s) at hand. I have another AR that functions flawlessly, and I have chosen to rehabilitate this AR (BAR-10) to full functionality, regardless of the time or effort involved. Don't tell me it can't be done, there is ample, even excessive testimony on this website that it can. On to the problem... I purcheaed the rifle used, at a gun show, serial number below 200. The seller claimed to have received the rifle in trade, and had never fired it. I noticed slight to moderate grooving on the casing shoulder, perhaps one round out of five, when manually chambering and ejecting ammunition, after I got it home. Power point ammunition would also have a quarter circle (1/16th to 3/32nd inch diameter, depending on depth and degree) carved out of the nose of the bullet, with the circle's center axis running perpendicular to the cylinder described by the casing. I sent it to Bushmaster for a functionality check. They replaced the bolt, though it had not cracked, presumably it was the old style bolt which was prone to cracking at the tail. They also did some machining on the feed ramp, and replaced both magazines. They pronounced the rifle fit, and when I tested it, most, perhaps 95%, of the grooving of the casings has been eliminated. It's more of a scratch than a groove now. Maybe one in ten casings manually cycled through the action see a very slight quarter circular deformation of the bullet tip, now less than 1/64th inch in diameter. I need 7 to 10x magnification to even see this. On the range, the rifle fires and feeds well most of the time. However, one round, usually but not always the last or second to last in a given magazine, out of perhaps 2 to 4 magazines, will jam sideways in the receiver before reaching the chamber. The jam has always achieved the same endstate, with the nose of the round midway up the feed ramp, one bolt lug face denting in the side of the casing one quarter inch below the shoulder, and the rear of the casing at or outside the ejection port. I believe that most or all of these rounds come from the right side of the double stack magazines. The jams occur with Winchester 168 gr power points, and Remington FMJ, all in .308. I have yet to try any 7.62 ammunition, though the rifle is chambered for either. I suspect the slightly longer cartridge will make the problem worse. The affected rounds have slight to moderate scratches along the casing between the rim and the eventual dent made by the bolt when it jams. The base of the casing appears pristine. There is some scratching on the cylindrical surface of the casing rim, but none on the base (flat) of the casing. From the reading I have done so far, it appears that the bolt is overriding the cartridges in the right side of the magazines, several magazines have been involved in these jams, but some magazines have been running smoothly. I have been marking the magazines to record each jamHalf of the ones tested have yet to jam, of theose involved in a FTC, most of them have jammed one time, and one magazine has been involved in three jams. At this point, I believe the problem to be magazine related, but not a systemic or design failure per se. If the design was flawed beyond repair, none of the cartridges would feed from any of the magazines, the jams would not be limited to the last one or two rounds in the magazine, and other people with this rifle would not report flawless operation. It could be a systemic tolerance issue, but even this should be correctable if I can isolate the variable that's causing it. One of the likely causes could be a weak magazine spring, or series of same. I have not checked the affected magazines as to whether they are inch type or metric, because I do not know how. Orher problems that might be the root cause here could be slight magazine lip deformations, follower issues, smoothness or tolerance issues in the feed ramps, gas issues causing short stroking, wear in the bolt lugs or bolt carrier, magazine catch issues, as well as others I have not thought of yet. For starters, I intend to perform a gravity check of gas ring functionality, and if someone here knows how to discern between metric and inch magazines, see if there is a related pattern to the magazines which run smoothly and those that are involved in jams. I will also take some pictures of the action and examples of the ammunition involved in the earlier grooving issue at the casing shoulder, and the later jam/dent/scratching issue I'm dealing with now. I can't do either of these today, my kids are here for the weekend, but I want to get this process started. Being inexperienced in this area, this is about all the concrete steps I know of to take. I want to make this rifle function reliably. I have it, I like the performance of the ammunition when compared to .223, I have ammunition for it, it has been zeroed, and I have a variety of magazines, cleaning materials, etc to complement it. It is an older rifle, but it is a robust platform, heavy and well made, it shoots well most of the time, I'm getting right at 1 MOA at 100 yards, and it just feels good in my hands. Besides those steps listed above, what should my next few moves be? I appreciate any help those more experienced can offer, thanks in advance for whatever you can contribute. |
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As always, photos would be nice, but not really needed. The rings on the bullet tips are being caused by the throat entry reaming not being completely broken in yet (read short throat lead). If you bore scoped the chamber, chances are you will find a bur ring at the throate start section that just hasn't been live fire smoothed out yet. As for the common scraps on the case at hand ejection, with the ejector cam'g the round off the side lugs, they will happen. During live fire, the case is pinned to the bolt face, and you will not have the problem. As for the mag feed problem, does sound like a weak mag springs. The one thing that I would check is to see just how much more room you can push the mags up to have the feed lips touch the bottom of the carrier. Granted that new springs may solve the problem, if the mags are sitting a tad low, a new or mod’d mag catch (shelf welded up a bit to retain the mags higher) may be wise to install as well. Also, check the front inside edge of the mags. Inward burs in the mags at this area will catch the bullet tip every time and cause problems. Here is a source for FAL extra power springs, http://www.gunsprings.com/RifleShotgun/1ndex.html Simply, just clean/lube the rifle like you would any other AR, Sweets for the bore to remove the copper fouling (completely removed before lubing), and CLP for the rest of the rifle (to clean, then lube the upper bearing surfaces). Since you have mag feed problems, install new spring in the mags (questionable units only if funds are low). And from there, get 500 rounds through the rifle to break it in, just like any of its 223 counter part, to allow the rifle/parts to settle in. At that point, post back if you still have problems and we can dive into cleaning up items by hand that did not so during live fire/break in. |
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Thanks for the link to the magazine springs. I believe the rifle has around 3000 rounds fired through it. There's no finish on any of the bolt carrier's bearing surfaces, and the hammer finish is worn off where it strikes the pin. The bolt appeared to have around 3000 rounds on it when I checked it against the bolt life estimation thread here, but I don't remember whether that was before or after BFI replaced it. The current bolt appears to have about 3000 rounds on it, no finish on the bolt face, pronounced halo around the firing pin port, finish wear on the locking lugs, but no material wear that I can really see. Here is what the rifle was originally doing during manual feeding, bfore I sent it to BFI:  The round on the left exhibits the groove on the shoulder, and the two rounds on the right exhibit the tip deformation I was experiencing. BFI did some grinding on the feed ramp and replaced the magazines, and both the grooving and tip deformation are significantly reduced, in quantity and in effect. You have to run a full magazine through the rifle to find a shoulder groove now, and it's only a scratch. Every once in a while a tip will show deformation under magnification. I forgot to mention earlier, BFI also replaced the stock that was on the rifle when I got it. It had a fixed skeleton stock, and they gave me a standard composite stock, at my request, at no charge. I think both stocks use the same buffer assembly, but I'm not sure. Here is what the jammed rounds look like after clearing the jam:  The dimples appear to have been caused by the four o'clock or 6 o'clock bolt lug, as seen from the rear of the rifle facing forward. The scratches on the left cartridge in the picture run from just above the rim to the dimple, with no visible damage to the rim below the groove, or on the flat face of the casing. In the pattern of parallel scratches, you can see where the bolt lug is rotating with respect to the casing or vice versa, moving from one corner of the bolt lug to the other. The left dimple clearly slants as it moved up and into the casing, as the tip of the round is already moving up the feed ramp when the bolt lug begins to dig in. In manually operating the bolt at very slow speeds, on the rearward stroke, I can get the bolt lug to "catch" in the casing's extraction groove, which tips the cartridge up to about a 30 degree angle. This has the effect of rotating the primer face of the casing to the rear, perhaps too far back for the front edge of the bolt lugs to catch the rear of the casing on the forward stroke, OR possibly making the upper edge of the rear of the casing too far down in the magazine for the front face of the bolt lugs to engage the rear of the casing. From there it acts like a short stroke, with the sharp corners of the bolt lugs dragging the cartridge forward and partway up the feed ramp until the bolt lug digs in and causes the jam. I do not know if this is what happens during semi-automatic cycling, or if the bolt really is short stroking, it happens too fast to tell, and also I am not in position to see it when firing. I know I have to put some more rounds through it, keeping track of as many variables as possible. Firing to date has been testing magazines for function only, and zeroing the rifle. I might have to send it back to BFI too, but since they've had it once and pronounced it good, I'd rather have a more specific idea of what's going wrong before I hand it off to the BFI techs. Does anyone know how to measure or otherwise tell if the FAL mags are inch or metric? Besides which magazines jam, and where in the magazine I am when jams occur, and what type ammunition seems most prone to jam, what other things should I be looking at while testing the rifle? Further, am I, or bystanders, or the rifle at risk testing it with this kind of cartridge damage being a possibility? There appears to be no impact or damage around the primer area, and I don't know if the powder can be ignited from impact alone. Thanks for your help so far, sorry to be asking so many questions, but I don't really understand what's happening here, and can't really search for information on my own without more to go on. |
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The bent bullets are the mags not getting the round up fast enough up after the carrier moved back and the rounds have force the top round back up tight against the feed ramps, or just place short cycling (if the bolt is not locking back after the last shot. Since I see the tag mark on the trailing edge of the first bullets rim, It's safe to say that the bolt face did make it past the rim of the case in the mag, just that the top round was not in position to be stripped correctly. Worn mag springs are most likely the problem, but I have to bring up stroking as well. On a normally full stroking rifle, the buffer bumper off the back of the receiver extension gives the rifle a little jolt, and this jolt will transfer to the mag to give it a little extra helping hand at getting the top round back up tight against the feed lips. Also, with this correct impact, it allows the buffer to correctly stall, which gives the mag even a little bit more time to recover than just the impact alone. Now the big question is if you have a buffer in the rifle, or just a plastic carrier extension. To figure this out, just pull the buffer and shake it. If it rattles, it's a buffer. To sum it up so far, it does still sound like the chamber is still on the tight/rough/new side, and will take a bit of live fire to break in. After this point, you should have good with full stroking, and if you do in fact have a buffer, the feed problems should go away once the questionable mags are rebuilt with new springs. |
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The buffer rattles, and appears more complex than a simple plastic tube. It has a clear plastic end cap held in place by a pin. I assume it is a buffer, not a spacer. The damage to the casing shoulder shown in the first of the two images above comes from a constriction in the upper edge of he magazine about wo thirds of way forward on the magazine. It is much more pronounced when slowly operating the mechanism, than when semi-automatic or full speed manual operation is performed. At slow speed, the bolt carrier will not move the cartridge forward in the magazine more than 1/4 inch before friction halts the forward progress. Clearly velocity and momentum play an important part of the action's functionability. At full rearward travel, the face of the bolt lugs are approximately one half inch behind the rear of the casing of the next cartridge in sequence. This is where the bolt lock engages. The rifle fails to lock open on an empty magazine perhpas one time out of six to ten. Not every time, not most of the time, but not rare either. I will repalce one magazine spring in a specially marked magazine that is known to fail, and perfom extensive testing to determine how this addresses the issue. this will take a week or two, since I'll have to order the stronger springs online, wait for delivery, and then scedule a trip to the range. I'll report back when I have more information. Thanks for all your help to date. |
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With the mag guide (the front section after the feed lips) making marks on the shoulder, I would remove a bit of the surface to allow the mag to guide into the barrel extension feed lips that are wider than a FAL feed section. As for the sporadic lock backs of the bolt on an empty mag, this could just be the upper bearing areas, and the chamber needs to break in a bit. Do check the end winds of the recoils spring to make sure that they are not protruding and scrapping down the inside of the receiver extension. On the B/C, do confirm that the key is not binding in the upper bearing track area, hence the B/C will pass a 45* downward free drop test with the carrier pulled back to the charging handle, then released to slip forward, and lock the bolt into the extension with the upper/lowered shot gunned open. Also take a look at the disco/trigger tail behind the hook. If you see denting or a white line at that area, then you may be getting hammer wedging. To cure this binding, you will remove .040 off the tail of the hammer to allow the hammer to be lowered by the bottom of the carrier, and not wedge up on the given area. As for the chamber/throat leaving marks on the ammo, if this is factory ammo, then it does leave somewhat of a concern. With these marking, it means that the bullet is somewhat imbedding at loading, and this can cause pressure spikes in the ammo when fired, and could also be the reason for the rifle full cycling or not, depending on the imbedding of the each round. (Read over function with the case more pressure bound to the chamber walls at unlock due to case going to a some what plasma state at the over pressurization. If you are getting ejector marks on the case rims, then this is defiantly holding true if the ammo is factory loaded). Again, Bushmaster is know to chamber on the tighter side, and if the chamber does break in and you are happy with what the rifle is producing for groups, you may be fine. If after something like 500 rounds, and with the mods/mag springs stated above, you still have problems with the rifle not full stroking (locking the bolt back on the last round), you may look into having the chamber reamed a true 7.62 nato. |
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