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Posted: 10/24/2008 6:46:14 PM EDT
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After reading through a lot of threads where people use the model 1 7.62 upper but get the MGI bolt and firing pin I am wondering what the problem is with the model one bolt and firing pin. From the sounds of it most people that have a problem with any 7.62 bolt needed a heavier hammer spring for the combloc ammo. If I read it right, having to file down the bolt face is only if using the 5.56 bolt. So why don't I see more of the model 1 bolts being used? Thanks |
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Just guessing on the model one. Never had one. I had a delton upper. The wolf crap ammo has recessed primers. The standard firing pin does not strike deep enough for the wolf primer. Other ammo is fine. One solution is to file the firing pin down and extend the strike about .007. I ordered a MGI bolt for mine. The first one was badly machined. The face of the bolt was bad. I waited about 4 weeks + for a replacement. I should have filed the firing pin. Would have saved a lot of aggravation. Not sure about exactly how strong the 7.62 model one bolt is. Most 7.62 upper have a rep for breaking bolts, but I never had a problem with mine. |
It's the actual bolt that breaks.  I've broken three and my friend amphibian has broken many more than that - see his post in >>> this thread. As to steel-cased (Wolf in particular) ammo, the primers are set a bit too deep for the standard firing pin protrusion and it needs to be lengthened and that can be accomplished in one of two ways. First, and I believe the best remedy is to spin-file the front of the FP collar by chucking it in a drill motor, the second way is to file the tail of the bolt itself - either way you want a FP protrusion of .039 |
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Bolt thrust but less material due to the larger case head. A standard 223 round running at 60k will have about 4240# of bolt thrust but it has more material for the locking lugs. A 7.62x39s working pressure is about 51500. Run the numbers and the bolt thrust is about 5400#. Run a 7.62x39 hot load thats 60k and the bolt thrust is 6450# |
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Quoted: Just guessing on the model one. Never had one. I had a delton upper. The wolf crap ammo has recessed primers. The standard firing pin does not strike deep enough for the wolf primer. Other ammo is fine. One solution is to file the firing pin down and extend the strike about .007. I ordered a MGI bolt for mine. The first one was badly machined. The face of the bolt was bad. I waited about 4 weeks + for a replacement. I should have filed the firing pin. Would have saved a lot of aggravation. Not sure about exactly how strong the 7.62 model one bolt is. Most 7.62 upper have a rep for breaking bolts, but I never had a problem with mine.  |
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Quoted: It's the actual bolt that breaks. http://i34.tinypic.com/219z9mu.jpg I've broken three and my friend amphibian has broken many more than that - see his post in >>> this thread. As to steel-cased (Wolf in particular) ammo, the primers are set a bit too deep for the standard firing pin protrusion and it needs to be lengthened and that can be accomplished in one of two ways. First, and I believe the best remedy is to spin-file the front of the FP collar by chucking it in a drill motor, the second way is to file the tail of the bolt itself - either way you want a FP protrusion of .039 Your friends with Robert? He actually told me the LMT has been the most reliable so far and Im pretty sure he has tryed them ALL. |
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