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Posted: 3/11/2007 4:39:36 PM EDT
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One year ago, I had a custom built AK-47 on an NDS-3 receiver and a Romanian parts kit. MCA was the builder. So far, it has been back twice. It still does not work. I think it is a heat build up problem. The gun starts malfunctioning after about 80-100 rounds. The bolt feels sluggish and does not freely go into battery. On a new mag, I have to "bump" it like you do with a Garand. Even then, the gun does not chamber properly. If I can get it to feed the round, it will fire and then fail to chamber the next round. Prior to heating up, the gun fires okay. When I brought it home (the gun is cool by then), the bolt seems to operate more smoothly. What should I do? What could cause this problem. I am hestitant to send it back to MCA. They seem like good people. I think they are trying. But, it seems to take a couple months to get it returned. I don't want to return it again just to get it back with the same problem. I want to resolve this ASAP. Should I ask for my money back for the build so I can send it to another gunsmith? I have thought about selling the thing. But, I can't do that and have a clear conscience with the buyer. I am frustrated. |
MCA did not manufacture bolt or any part of your gun ... If it headspaces within specs, don't blame the builder for your over-heating of the bolt or the entire gun for that matter. |
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If you decide to open up the upper rails, check first that there isn't a burr on the underside. If the rails are milled with a dull tool, there can be a huge burr on the underside and it will make the carrier stick. If it's there you can remove the burr with a dremmel tool and heavy duty cut off wheel. |
Original Poster stated that the gun was back to MCA twice. I'm sure that MCA would catch such obvious burrs. Besides, he has no problem with the carrier, only the bolt. Most likely his problem begins when he over-heats the action to the point of failure. The shooter does not need a new gun ... rather, the gun needs a new shooter. |
With AKs, troubleshooting is best done from simple to complex. I will also say that if it's been back to the builder twice, then their troubleshooting is suspect (no jab to MCA, I have no experience with them and my comment is a generality aimed to help the Poster get his gun running). The bolt can bind up if there is a problem with the carrier to upper rail clearance or alignment....especially in the lock up where Poster said the issue is. He can check for a burr in less than 30 seconds, and IMHO this should be checked before considering widening the upper rail. |
Sir, with all due respect, are you familiar at all with this person's shooting practices? Did he ever says he bump fires 1,000 rounds in 30 minutes and it seizes up then? Don't be rediculous. Most of us have gotten our AKs pretty hot and have never had them seize up. It's not a known problem and it's not common by any means. The bolt carrier on an AK dosn't even get that hot. Neither does the receiver. Most of the heat due to firing tends to be focused on the gas tube, barrel, front sight base, gas block, and gas piston. There's either something wrong with the receiver or something wrong with the bolt carrier. The rails on the receiver could be burred. This is unlikely as the builder would have likely caught this problem and corrected it. Especially by now. Perhaps they are slightly too thick, unlikely again, but theoretically possible. More on that later. The grooves on the sides of the bolt carrier that fit on the receiver rails could be burred. Unlikely again, especially considering his parts kit was likely used. They could be too small. Not likely either, but possible. See, it's possible that the receiver sheet could be a wee bit too thick - on the heavy end of it's tolerance, and the bolt carrier grooves could be a wee bit too slim, on the lower end of their tolerance. This could create an unusually tight fit between the bolt carrier and receiver, one that when one introduces a little heat from firing, causes the rifle to seize. You should try a different bolt carrier if you have access to one. Be warned that you must use your original bolt for headspacing reasons, just exchange the carrier itself. Also, try your carrier in another rifle. If his carrier jams in your rifle, it's probably your receiver. If your carrier jams in his rifle, it's likely your carrier. If both work after exchanging, it's probably a tolerance problem along the lines as the one I've described above. Your receiver rails may be a bit "tight" as well, meaning the inside edge of one rail ro the inside edge of the other may be too close. If you have access to other AKs whose function you're sure of, try measuring the distance between the rails. Compare the distance to yours. If yours is narrower, you can see that this may cause a problem. In other words, this is not just a heat problem. I've never heard from anyone who claimed to have this problem in the past, I've never seen it on these or other boards, even amongst bumpfiring freaks. There's likely either something manufactured/installed/assembled incorrectly, or there's a tolerance problem. |
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Richard, I fired 10 rounds. I casually loaded another 10 rounds and fired them. I continued this until the 100 round mark. I then saw the failure conditions I mentioned. Not a shooter problem. MCA said that everything on the receiver measured within specification. I have looked for burrs and not found any. |
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I have offered to buy the gun back from Dave. We have spent over $50 in ammo test firing it and over $100 in shipping costs as it has gone back and forth between the two of us. We have sent him video of the gun functioning perfectly-- he is offering to send us video of the gun jamming. I have checked everything I can think of and the gun works fine for us. I can't think of anything else to tweak. So far: headspaced three times Polished chamber Hand smoothed rails Hand smoothed ejector Polished certain trunion areas checked all areas that move against each other for burrs or roughness double/triple/quadruple checked gas system including trying three different gas pistons using three different bolt carriers that each had a foreign/original, TAPCO, and RSA piston installed. We have fired the gun until its gotten hot. We have fired the gun until it was full of carbon and unburned powder. We can't get it to fail, even using different magazines. It even runs with a Chinese 75 round drum. We've fed it soft point ammo in an attempt to get it to choke. The carrier handle reciprocates freely, its an NDS receiver not a pinched Armory USA, and I've measured everything I can think to measure. Its hard to see what's "wrong" with the gun when it works fine for us. I have no idea why this gun would work fine in Missouri and fail in California. It appears this gun will now be returned to us for the fourth time. I'm sick of even thinking about it. If Dave agrees to sell it back to us, he will not be out any money for the build, and I may post video here on ARFCOM of me smashing this fucking gun against a brick wall. Either that or drill a third hole, notify BATF that I've manufactured a post-sample NFA, and melt the shit out of it on full auto. Maybe then it will jam for me. |
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I took the gun apart again this evening. The bolt carrier travels freely for the first 1/3. After then, the carrier starts to drag on the sides of the receiver rails. I have some up and down movement. But, absolutely no side to side movement on the carrier. It is wedged and rubs the receiver. I put a different carrier in the gun and it literally glides through all the way forward and back. It can move side to side very slightly as I move it back over the entire range of travel. There is absolutely no burrs anywhere on the (problem) carrier guide slots. it is very smooth. What should be done now? 1. Buy a new carrier? 2. File down the receiver where it is binding? 3. Modify the carrier? I am not going to do anything until I get good advice. |
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Here is the point where the carrier starts to drag on the side of the receiverhttp://i69.photobucket.com/albums/i58/dave3006/100_0927.jpg |
| As it travels back towards the end, it is very tight herehttp://i69.photobucket.com/albums/i58/dave3006/100_0928.jpg |
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Sounds like a new carrier should be test fired.... and I think that's good news. Can you test fire it with the carrier that seems to fit better? I'm sure I have one around here off a romy kit, if you don't have another option IM me and we'll work something out that makes sense to get this gun up and running. I've never seen a romy carrier with out of parrallel rail guides, but you may be the lucky winner... |
That right there very may well be the problem. It could have been an issue with the bolt carrier from the parts set being slighty out of spec but with the original rifles receiver it may have worked perfectly. Can you install the other bolt carrier in the rifle and take it out and see if it has cured the problem. If it does then you can replace the bolt carrier and probably have no more problems. Does your original bolt carrier use a US gas piston as a compliance part. K-VAR has Romanian bolt carriers............... If you supplied the parts kit for the build and the receiver and it is a bolt carrier out of spec issue then I don't believe MCA is responsible. They can only use what you supply them with. You may also try a thin layer of synthetic grease in the area of the binding first. As the rifle heats up it would increase the lubricity in that area with the replacement carrier. If you need another bolt carrier with a US piston I have an unserial numbered one though it isn't the greatest in appearance. It would probably need to be painted to match your rifle. I have a blast cabinet and could have it blasted and ready for a coat of molyresin. Try the other bolt carrier you have first and see if the rifle still malfunctions. Some Mobile 1 synthetic grease in a very thin layer or some miltec grease may help. If the rifle functions after that then the issue is solved. I see TheNorm was posting along the same lines as I was. I don't have any idea what country the bolt carrier I have is but I have tried it in several countries AKs with no issues. Here are two of us who have bolt carriers that you can obtain cheaper than K-VAR most likely so if this is the problem with your rifle it can be solved at a lower cost for both you and MO Custom Arms. All you have to do is take the rifle out with the replacement carrier and see if this is the issue. |
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In that area there shouldn't be any binding, however pulling the charging handle back should get noticeably more difficult, not due to the receiver pinching in but because the carrier is being pushed upward by spring pressure from the hammer underneath it. To make sure its the receiver, remove the fire control group and try it again. It shouldn't pinch at the rear, we measured it and believe the receiver is in spec. Also, as I noted above, we tried three different bolt carriers with different pistons installed and the gun shot the same way every time, none of them hung up or slowed the action. |
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