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Posted: 8/6/2009 1:02:27 PM EDT
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This is no doubt overly obsessive, but I'll ask anyhow.
1. Bolts: Can someone confirm for me that Carpenter 158 is the current mil-spec material for bolts? Is that a recent change from the original material? Are most commercial bolts made from Carpenter 158? Lastly does anyone know what material Young Manufaturing bolts are made from, or who makes them for Young? 2. FCG parts: Can anyone confirm that casting is the current mil-spec? Does anyone remember the name of the manufacturer of the FCG parts marked with "SS"? Are those cast or MIMed? Are any of the ones we see MIMs? 3. Receiver Extensions: Is mil-spec 7075? What are all the ones available made from? 7075? 6061? Does it matter in this application? Sorry for the length. These are the questions I never find answers to. It seems like every time one of the above is asked, the thread degenerates into a bitchfest over who's got the best lower parts kit or who has an MP'd bolt. Thanks in advance for any responses. |
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Quoted:
This is no doubt overly obsessive, but I'll ask anyhow. 1. Bolts: Can someone confirm for me that Carpenter 158 is the current mil-spec material for bolts? Is that a recent change from the original material? Are most commercial bolts made from Carpenter 158? Lastly does anyone know what material Young Manufaturing bolts are made from, or who makes them for Young? 2. FCG parts: Can anyone confirm that casting is the current mil-spec? Does anyone remember the name of the manufacturer of the FCG parts marked with "SS"? Are those cast or MIMed? Are any of the ones we see MIMs? 3. Receiver Extensions: Is mil-spec 7075? What are all the ones available made from? 7075? 6061? Does it matter in this application? Sorry for the length. These are the questions I never find answers to. It seems like every time one of the above is asked, the thread degenerates into a bitchfest over who's got the best lower parts kit or who has an MP'd bolt. Thanks in advance for any responses. receiver were 6061 (T5 i believe) but were upgraded to 7075 T6 after trials in Vietnam where the high humidity created corrosion issues. the Annodizing was upgraded from Type II to Type III. Thats what I know. Okki |
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The mil tests show that the bolts(8620) used in Nam started showing fatigue cracks around 3000 rounds, most failed by 5-6000. They changed to carpenter 158 after that and gained apx 1500 rounds from what I read, the 158 is more corrosion resistant so that slows the forming of corrosion pits that is the starting point for the cracks.
Most commercial bolts on the market today are 8620 which is softer metal than 158, there are only 3 companies that use the correct mil spec 158. Two of those companies only make 5.56 bolts and most of those go to Colt and FN for DOD contracts the third company is more than likely CMT although I cannot confirm that. |
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Look them up.
They are all here. Have fun. http://www.everyspec.com/ |
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Quoted:
Two of those companies only make 5.56 bolts and most of those go to Colt and FN for DOD contracts the third company is more than likely CMT although I cannot confirm that. 5.56 Bolts? .223 & 5.56 are IDENTICAL case head size! the ONLY difference between the two is in the throat of the chamber (just in front of the bullet when chambered) PursuitSS |
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5.56 Bolts? .223 & 5.56 are IDENTICAL case head size! the ONLY difference between the two is in the throat of the chamber (just in front of the bullet when chambered)
I believe his meaning was that those manufacturers do not make 6.8, 6.5, 5.45, 9mm or any of the other calibers in which they make AR models. |
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