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Posted: 3/3/2019 12:00:36 PM EDT
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I posted a poll earlier attempting to document the number of broken 7.62x39 bolts that people might have encountered. Despite sobriety, the poll was all over the place and failed to exclude user-repairable malfunctions like broken extractors, etc. It also, IIRC, was limited to AIM bolt carriers. It was a train wreck, I feel the shame of disgrace, and apologize. What I would like to find out, is, how many people here have experienced an actual breakage, whether it be the lugs or the thin metal wall around the case rim. Not including extractors. My thinking is, since many people carry spare extractors (you DO carry a spare extractor, right?) that repair is easy enough to make even while at the range or in the field. I'm talking about a potential "day-ending" failure of the bolt altogether that requires a whole new bolt. And if you have experienced a failure, please, PLEASE note in the comments the brand and approximate round count before you leave. Bfoosh06 also suggested adding data about barrel length and gas system length if you had a failure. Thanks! Caser pointed out that it might be good to specify round count for bolts that have continued to work without issues, so please include that data as well. So, poll inbound. Although not scientific, this will give us an idea of how many bolt lug failures that users are experiencing with their 7.62x39 bolts. Maybe this will either set our minds at ease, or make the panic well up within our souls until it consumes us finally. |
You have probably seen my picture below:
I took that picture around 2003 or so. Back then, you didn't have many options for quality bolts. Regarding your poll and round counts, I find it comical you don't even know your own round count as you posted in this thread: https://www.ar15.com/forums/AR-15/What-s-up-with-7-62x39-now-/121-736862/ I broke all my bolts in full auto in 7.5" uppers running 75 round drums... https://www.youtube.com/watch?v=L0HxzM8f8LU I recall using some DPMS bolts where it only took ONE round to break it. I swapped for another new DPMS bolt and snapped the second one in ONE round again. These days much higher quality bolts with all the competition. I have a cheapo PSA 7.62x39 bolt and haven't broken it in the same 7.5" 7.62x39 uppers that were breaking the old bolts. |
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Quoted:
Regarding your poll and round counts, I find it comical you don't even know your own round count as you posted in this thread: https://www.ar15.com/forums/AR-15/What-s-up-with-7-62x39-now-/121-736862/ It seems to me that the choice of materials in later bolts has improved the reliability of them. Your post bears that out. |
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Quoted:
You have probably seen my picture below: http://c3junkie.com/wp-content/uploads/2016/11/all.jpg I took that picture around 2003 or so. Back then, you didn't have many options for quality bolts. Regarding your poll and round counts, I find it comical you don't even know your own round count as you posted in this thread: https://www.ar15.com/forums/AR-15/What-s-up-with-7-62x39-now-/121-736862/ I broke all my bolts in full auto in 7.5" uppers running 75 round drums... https://www.youtube.com/watch?v=L0HxzM8f8LU I recall using some DPMS bolts where it only took ONE round to break it. I swapped for another new DPMS bolt and snapped the second one in ONE round again. These days much higher quality bolts with all the competition. I have a cheapo PSA 7.62x39 bolt and haven't broken it in the same 7.5" 7.62x39 uppers that were breaking the old bolts. eta: dang, out of stock. 
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3 blown lugs and 2 extractors on 7.62x39 pistol. 1 blown lug and 2 extractors on a .264 lbc which uses the same bolt. Less than 4000 rounds total on the .264. Less than 1500, maybe 1000 on the pistol. Miscellaneous bolts none of which I can remember. I pretty much got what I could get. One company blew one lug and one extractor and they went out of business. I have the LMT in the pistol now but don't have a lot of rounds through it. I still shoot the .264 but don't shoot the pistol very often now. Most of the breakage on the pistol was about 4 years ago. I replaced the last extractor on the 264 with a Spinta and have maybe 300 rounds on it. 2 of the lugs on the 7.62 lasted less than 200 rounds.
I do know that Aim didn't have any in stock during the time I was breaking most of them. |
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11.5" Model 1 upper.
Model 1 bolt broke off part of thin metal wall around case rim and 1 lug adjacent to the extractor cut out at round #919. Replaced with AIM bolt. 370 rounds now fired with AIM bolt and no breaks so far. All rounds fired semi-auto. Multiple brands of steel case ammo have been used. |
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Thanks for the data, guys. Even without brand names, that's still good info because of the time frame. So many variables that can't be accounted for in a poll. For example, it seems like most of the failures come from the earlier bolts. IIRC, it was that way in the earlier thread/poll that I posted. More data is welcome! |
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Quoted:
Thanks for the data, guys. Even without brand names, that's still good info because of the time frame. So many variables that can't be accounted for in a poll. For example, it seems like most of the failures come from the earlier bolts. IIRC, it was that way in the earlier thread/poll that I posted. More data is welcome! I think your last poll showed a 17% failure rate. at least this one is consistent with the last one in terms of failure rate. |
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Quoted:
https://www.ar15.com/forums/AR-15/Has-anyone-experienced-a-failure-with-Aim-Surplus-7-62x39-bolts-yet-/121-733648/?page=1&anc=bottom#bottom I think your last poll showed a 17% failure rate. at least this one is consistent with the last one in terms of failure rate. That's why I was unwilling to draw any conclusions the last time, but this time, we have some explanations to back up the data. Even so, from the comments, most of the failures SEEM to be older bolts. |
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I believe that short barreled pistol/sbr/carbine length gas systems puts extra stress on a already thinned out
bolt head originally cut at ~.380" then bored out to ~.446"... Going full auto and using a suppressor can also add additional complications to the mix as well, which can put yet more additional stress on the bolt assembly and recoil system... I would recommend to my friends for most uses (AR-15) for people to go with a Mid Length or Rifle Length gas systems to help avoid bolt failures in the DI gas system... Lets face it, the 7.62x39mm round was never designed to function in a DI AR-15 platform...but that doesn't mean it can't be smoothed out to run reliably using good ammo, mags, enhanced firing pin, tuned bolt, etc. |
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Quoted:
I believe that short barreled pistol/sbr/carbine length gas systems puts extra stress on a already thinned out bolt head originally cut at ~.380" then bored out to ~.446"... Going full auto and using a suppressor can also add additional complications to the mix as well, which can put yet more additional stress on the bolt assembly and recoil system... I would recommend to my friends for most uses (AR-15) for people to go with a Mid Length or Rifle Length gas systems to help avoid bolt failures in the DI gas system... Lets face it, the 7.62x39mm round was never designed to function in a DI AR-15 platform...but that doesn't mean it can't be smoothed out to run reliably using good ammo, mags, enhanced firing pin, tuned bolt, etc. I even use ASC mags, and everybody swears that they don't work, but mine just keeps running. |
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Quoted:
7.5" barrel and only 50 rounds down the tube. Can't get steel ammo to function 100% yet and have around 3k rounds for it to eat. LMT bolt hasn't had an issue so far. I really need to get this pistol to the range again and work out the bugs.... |
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