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The Range
Firearms Chat
7.62x39 10 inch barrel, help
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<blockquote data-quote="joegrizzy" data-source="post: 3936285" data-attributes="member: 45524"><p>i've dealt with getting a 7.62x39 short barrel upper to run. there's a good bit of info you can find about the manufacturing of the bolt itself, but mostly from what i can recall the gist is:</p><p></p><p>>earlier model used a 5.56 bolt and just milled the face to accept the 7.62x39 case, which has a thicker rim than 5.56.</p><p>>the shaving of the bolt face led to the lugs on the bolt receiving a different amount of force due to different dimensions from the alterations to the bolt face.</p><p>>this would lead to situations wherein lugs would dig/drag/wear, carrier tilt could occur, you can find reports on forums of ALL sorts of "maybe it's this, look at this" type posts</p><p>>in later models that were made with dedicated bolts, this issue supposedly doesn't present itself as much</p><p></p><p>i'll link just a *few* posts that came up when searching today, i *know* i've read several of these when i had issues.</p><p></p><p>[URL unfurl="true"]https://www.65grendel.com/forum/archive/index.php/t-24276.html[/URL]</p><p></p><p>[URL unfurl="true"]https://www.northwestfirearms.com/threads/7-62x39-ar-issue.300931/[/URL]</p><p></p><p>[URL unfurl="true"]https://www.theakforum.net/threads/7-62x39-ar-15-build-questions.314499/[/URL]</p><p></p><p>after doing LOTS of autismo research, what i *personally* think is causing this issue for MOST people is simply a gas issue.</p><p></p><p>while i agree about the bolt issues, and trying to source who *actually* made the one you are looking at can be trite, from my personal situation, i cogged it something like this:</p><p></p><p>>trigger pulled</p><p>>firing pin hit primer</p><p>>bullet go bang</p><p>>sometimes the bolt wouldn't even go back, or if it did, imperceptibly</p><p>>bullet definitely exited</p><p>>spent case seems "stuck" (this is because the force of the bullet going boom usually cycles and extracts for you; extracting a spent round manually is usually "harder" in most guns due to the case being swollen and is just a weird phenomenon thing; it's not really harder to extract than it would normally be. usually when something is amiss, people start being "careful" and being "careful" and then trying to say manipulate a charging handle to eject a spent case that has swelled a bit after firing you probably aren't going to be using your normal amount of dummy force, so you'll think it's "harder" or "stuck" because you aren't just he-manning it like usual)</p><p>>get case out, looks fine</p><p>>load another round</p><p>>pull trigger</p><p>>firing pin hit primer</p><p>>bullet go bang</p><p>>same thing</p><p>>bullet must be exiting barrel before enough gas gets thru gas system to force open bolt and force ejector to function</p><p>>gas taking path of least resistance and following the barrel after the bullet exits</p><p></p><p>might not be the most "suggested" solution, but i widened my gas port by drilling it out a teeeeny bit and it literally made ALL the difference in the world. i think the whole thing is a gas issue that leads to other problems because their isn't enough force in the system to really function it properly and stuff doesn't move like it should, resulting in odd hang-ups or unusual wear patterns/dragging.</p><p></p><p>you can test this by using a suppressor or even a fake one. any long enough muzzle device would test this because then the gas wouldn't escape *quite* as quickly and more of it should theoretically go thru the gas port and thus cycle the rifle properly. many people in many posts reported their firearms working fine with a can or long brake, but not without. this was because it's a gas issue.</p><p></p><p>too long; didn't read: not enough gas going thru gas port before bullet leaves barrel. make gas port wider for more gas, rifle functions.</p></blockquote><p></p>
[QUOTE="joegrizzy, post: 3936285, member: 45524"] i've dealt with getting a 7.62x39 short barrel upper to run. there's a good bit of info you can find about the manufacturing of the bolt itself, but mostly from what i can recall the gist is: >earlier model used a 5.56 bolt and just milled the face to accept the 7.62x39 case, which has a thicker rim than 5.56. >the shaving of the bolt face led to the lugs on the bolt receiving a different amount of force due to different dimensions from the alterations to the bolt face. >this would lead to situations wherein lugs would dig/drag/wear, carrier tilt could occur, you can find reports on forums of ALL sorts of "maybe it's this, look at this" type posts >in later models that were made with dedicated bolts, this issue supposedly doesn't present itself as much i'll link just a *few* posts that came up when searching today, i *know* i've read several of these when i had issues. [URL unfurl="true"]https://www.65grendel.com/forum/archive/index.php/t-24276.html[/URL] [URL unfurl="true"]https://www.northwestfirearms.com/threads/7-62x39-ar-issue.300931/[/URL] [URL unfurl="true"]https://www.theakforum.net/threads/7-62x39-ar-15-build-questions.314499/[/URL] after doing LOTS of autismo research, what i *personally* think is causing this issue for MOST people is simply a gas issue. while i agree about the bolt issues, and trying to source who *actually* made the one you are looking at can be trite, from my personal situation, i cogged it something like this: >trigger pulled >firing pin hit primer >bullet go bang >sometimes the bolt wouldn't even go back, or if it did, imperceptibly >bullet definitely exited >spent case seems "stuck" (this is because the force of the bullet going boom usually cycles and extracts for you; extracting a spent round manually is usually "harder" in most guns due to the case being swollen and is just a weird phenomenon thing; it's not really harder to extract than it would normally be. usually when something is amiss, people start being "careful" and being "careful" and then trying to say manipulate a charging handle to eject a spent case that has swelled a bit after firing you probably aren't going to be using your normal amount of dummy force, so you'll think it's "harder" or "stuck" because you aren't just he-manning it like usual) >get case out, looks fine >load another round >pull trigger >firing pin hit primer >bullet go bang >same thing >bullet must be exiting barrel before enough gas gets thru gas system to force open bolt and force ejector to function >gas taking path of least resistance and following the barrel after the bullet exits might not be the most "suggested" solution, but i widened my gas port by drilling it out a teeeeny bit and it literally made ALL the difference in the world. i think the whole thing is a gas issue that leads to other problems because their isn't enough force in the system to really function it properly and stuff doesn't move like it should, resulting in odd hang-ups or unusual wear patterns/dragging. you can test this by using a suppressor or even a fake one. any long enough muzzle device would test this because then the gas wouldn't escape *quite* as quickly and more of it should theoretically go thru the gas port and thus cycle the rifle properly. many people in many posts reported their firearms working fine with a can or long brake, but not without. this was because it's a gas issue. too long; didn't read: not enough gas going thru gas port before bullet leaves barrel. make gas port wider for more gas, rifle functions. [/QUOTE]
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