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Posted: 10/15/2002 5:19:35 PM EDT
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I took care of the feeding problems with the MISR90 by altering the feed ramp and polishing. Now for the big problem. After I fired around 60 shots, the bolt would not close completely after a round was fed. After some inspection, the bolt carrier and bolt were slightly deformed. It looks like the bolt would not rotate when the rearward movement began and the it would slam into the carrier and deform the groove where they mate together. The previous owner had the same problem and had a gunsmith take the burrs off, only to have them return after a little firing. Now for the questions. Has anyone had this same problem? Is there a hardening problem with the bolt and carrier, or is there something else causing the binding? If replacement parts is the answer, what country of origin should I use? The MISR90 is an Egyptian receiver with Chinese parts put together by Century. If the Chinese parts are the problem, I don't want to use the same parts as replacements. Where can I get the needed replacement parts? Somebody please help, I don't want such a large paperweight. Thanks, [email protected] |
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Hi there Hawgleg. What you are describing is an unusual problem. I have seen it before, but mostly on AK's that are "bumped" a lot. Here's what I want you to do. Clean your gun and take the bolt out of the carrier. For safety's sake, you should probably remove the hammer and spring as well. Place an unfired round in the bolt face and insert into the chamber. This is just to see that you do not have short headspace. The bolt should close and rotate into the locked position easily and not have any forward/backward play. Well, at least very little play. If the bolt is closing easily, is not hard to rotate into the locked position with an unfired round in the chamber, then I'm confident it is not an issue with chamber and bolt dimensions being too tight. What normally causes this is the gun has chambered a round, the hammer has fallen and fired the round and the bolt is not fully closed. The carrier is still traveling forward and the slot in the carrier strikes the lug on the bolt, which can no longer rotate because the chamber pressure has locked it tight against the locking lugs. This might be caused by bolt bounce as well. If there is lots of play from front to back, there is the possibility the same problem could be caused by too loose a fit on the headspace. This would be a bad situation. There would be significant wear on the locking lugs on the bolt which could lead to a major failure and injury. To complete this troubleshooting thing, I'll need some more information or pictures of the bolt lug. The fix will probably be a new bolt and carrier. Another tip. Unless your bolt carrier is highly polished stainless steel, it probably is not Chinese. The heat treat is not great on the Egyptian equipment. If you can provide some more information, I could comment further. |
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a slight deburring of the locking lugs on both the bolt and trunnion may be needed...but don't touch the mating faces of the lugs. the carrier cam slot and bolt cam may also need stoned to smooth them out. also, a quick check of the gas tube and piston to eliminate any possible binding should be performed. if you have access to go/no go headspace gages available (local smith), a check on the current headspace is in order. in the meantime, follow mg34ss' advice with a live round (use extreme caution!!!) and see if you can give us some more data. |
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Thanks for all the info. I'll try to get some pics of the problem area this weekend, I don't have a digital camera. One statement jumped out at me. The rifle normally feeds well now, but sometimes the bolt does not close completely. I know the hammer slammed home the bolt when fired a few times. As for the hardening, I don't know how hard the bolt and carrier are supposed to be. I took a fine file to the bolt and it filed down easily. The bolt and carrier are not polished steel. They are a dull finish. Maybe they are Egyptian parts. I do have a Bulgarian parts kit here, but I'm assuming the milled/stamped parts are different. I tried chambering the live round. I have to take the burrs off the parts before I can really tell, but there seemed to be a little resistance when closed with no bolt play. Where do I get replacement parts? What country of origin should I specify? Thanks again. I'll get more info asap. |
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