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Posted: 10/6/2009 1:38:27 AM EDT
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I have a 7.62 X 39 upper. This past weekend I broke the extractor shooting some wolf steel case ammo.
I know there is a difference between the 5.56 and 7.62 extractor, but when looking at them side by side I really can’t see any. Does anyone know what the differences are 
Thanks Jim |
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broke the extractor on my wife's 7.62x39 a few months ago. (shooting Wolf too) Fortunately, we have a spare bolt––-I pulled the new bolt out of the package and had a "hmmmm" moment.
I compared a MGI to a DPMS 5.56 extractor––-identical. **don't know if that's because somebody accidentally put a 5.56 extractor on a 7.62x39 bolt at the factory, but she's put more than 500 rds down range since the swap without a problem. |
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I've broken a lot of 7.62 bolts and extractors, there definitely is a difference. The 7.62 extractors are cut deeper.
Unless the bolt was specifically designed to use a 5.56 extractor. AR15 performance makes a bolt that is specifically designed to use 5.56 extractors. http://www.ar15performance.com/inc/sdetail/339 Never tried one of their bolts. I've been using the LMT and think it is best. Haven't broken one of those yet. Here's a pic of some of the bolts I've been through. 
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Quoted:
I've broken a lot of 7.62 bolts and extractors, there definitely is a difference. The 7.62 extractors are cut deeper. Unless the bolt was specifically designed to use a 5.56 extractor. AR15 performance makes a bolt that is specifically designed to use 5.56 extractors. http://www.ar15performance.com/inc/sdetail/339 Never tried one of their bolts. I've been using the LMT and think it is best. Haven't broken one of those yet. Here's a pic of some of the bolts I've been through. http://www.c3junkie.com/m16/762/all.jpg Will a 5.56mm extractor grab a 7.62 rim enough for reliable extraction? Any idea what metallurgical difference there would be in the 7.62 bolts that lets their lugs break like that? |
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Hey Robert, is that you?!? That's funny because I started reading your post and it made me think of you . . . didn't realize it probably was until I saw the website on the picture. But, I don't mean to hijack the thread so take care!
Adam Quoted:
I've broken a lot of 7.62 bolts and extractors, there definitely is a difference. The 7.62 extractors are cut deeper. Unless the bolt was specifically designed to use a 5.56 extractor. AR15 performance makes a bolt that is specifically designed to use 5.56 extractors. http://www.ar15performance.com/inc/sdetail/339 Never tried one of their bolts. I've been using the LMT and think it is best. Haven't broken one of those yet. |
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Quoted:
Will a 5.56mm extractor grab a 7.62 rim enough for reliable extraction? Any idea what metallurgical difference there would be in the 7.62 bolts that lets their lugs break like that? The case is larger in 7.62 and so the extractor has to be cut deeper. The radius' are different. However, like AR15performance is doing, it can be made to work. I haven't seen one of their bolts. But tinkering with a 5.56 extractor in a 7.62 bolt I had problems with the extractors being too tight with any spring I tried. I'm thinking if you milled a shallow hole in the bolt to recess the spring a little it would work. Again, just guesses. Regular 5.56 bolt break under heavy use. With the larger case of the 7.62x39, the sides of the bolt are much thinner surrounding the head of the case so the situation is much worse. Making engineering changes will help such as doing stress relief cuts on the lugs like LMT has done. Changes to stronger material also helps. LMT has done BOTH. I have no personal experience with any other 7.62 bolt that has both advantages which is why I stick to using those. I run mine very hard. All full auto from a 7.5" barrels using 75 round drums. 
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