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Originally Posted by 79S
If that 1/4 bit don’t work move up to a 5/32 that should get that AR running for sure..

you want the bullet going out the muzzle , not the gas port!! grin


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Originally Posted by antelope_sniper


Harbor freight sells them as well.


I prefer to use good drill bits, not Hobo Freight junk, and wouldn't dare put a HF drill bit in a good barrel. You want to avoid creating a burr on the inside, and starting with a good sharp drill bit that cuts well is pretty important.

Most of their equipment of this nature is only adequate for woodworking anyway. It's getting hard to find good gear on Amazon too, unless you really know what brand you're looking for; there is so much low quality chinese junk being pushed there that it's hard to find the good stuff sometimes.

High quality drill bits are not very expensive, and are easily available from reputable places. McMaster, Fastenal, and Brownells are my main choices, MSC and Grainger if I have to.
I do a lot of metal machining and have learned a long time ago to not waste money on junk drill bits.

Edit - figured I should clarify the recommendations here: there are a bunch of good brands of drill bits, so it's not worth listing them all. Easy choice is to order them from McMaster Carr; they don't sell junk and if you order the right bit for the job, it'll do what you need. A 135° split point HSS stub drill is what I prefer, don't want carbide for this. A tip to reduce the amount of burr in the hole is to drill a couple number sizes smaller first, then finish with the correct size only removing about 5-6 thousandths. Also, for drilling gas port holes I only use the final size drill once or twice, then set it aside for other jobs. This has given good results for me in a bunch of SS and CM barrels.

Also, if you're using a drill press instead of a mill, put a cleaning rod in the barrel before drilling, it'll stop the drill from touching the far side of the barrel.

Last edited by Yondering; 05/14/20.
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Remember to back the port up with a lead slug if you drill it.


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Originally Posted by Yondering
Originally Posted by antelope_sniper


Harbor freight sells them as well.


I prefer to use good drill bits, not Hobo Freight junk, and wouldn't dare put a HF drill bit in a good barrel. You want to avoid creating a burr on the inside, and starting with a good sharp drill bit that cuts well is pretty important.

Most of their equipment of this nature is only adequate for woodworking anyway. It's getting hard to find good gear on Amazon too, unless you really know what brand you're looking for; there is so much low quality chinese junk being pushed there that it's hard to find the good stuff sometimes.

High quality drill bits are not very expensive, and are easily available from reputable places. McMaster, Fastenal, and Brownells are my main choices, MSC and Grainger if I have to.
I do a lot of metal machining and have learned a long time ago to not waste money on junk drill bits.

Edit - figured I should clarify the recommendations here: there are a bunch of good brands of drill bits, so it's not worth listing them all. Easy choice is to order them from McMaster Carr; they don't sell junk and if you order the right bit for the job, it'll do what you need. A 135° split point HSS stub drill is what I prefer, don't want carbide for this. A tip to reduce the amount of burr in the hole is to drill a couple number sizes smaller first, then finish with the correct size only removing about 5-6 thousandths. Also, for drilling gas port holes I only use the final size drill once or twice, then set it aside for other jobs. This has given good results for me in a bunch of SS and CM barrels.

Also, if you're using a drill press instead of a mill, put a cleaning rod in the barrel before drilling, it'll stop the drill from touching the far side of the barrel.


Thanks Yondering.

Good stuff.


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I just went out and measured, no drilling with a normal standard drill bit and a 3/32” fit in the gas port just fine.

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Pardon if I missed it, but what length is the barrel? What gas length?

On a 20" you could stand going up to a #41 or even 42, maybe 43.

A 7.62x39 is going to need little bigger port than a 5.56. My references say a .078" port with carbine buffer is going to run a mid gas 16" 5.56. If that's the case, I'm guessing 3/32" is probably going to be a little too large.


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Tyrone,

It’s a 16” barrel with carbine length gas tube.

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Originally Posted by MontanaMarine
If the bolt won't let the brass case go, maybe check the ejector plunger/spring for crud.

also maybe compare rim diameter between the steel and brass cases. If the brass ammo has oversized rim diameter, that might be an issue depending on boltface diameter.


I compared the rim diameter between the steel case I have on hand and two different brass ones, all three are identical in size.

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Originally Posted by Hudge
Tyrone,

It’s a 16” barrel with carbine length gas tube.
Colt 6920's have a .062" gas port.

Perhaps someone here with a similar barrel that runs well could share their port size.

Last edited by Tyrone; 05/16/20.

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I have no idea what size port a 7.62x39 would run but we need to know if he's having a failure to eject or failure to extract problem before we can offer ideas in the right direction.

But I have a feeling he's just screwing around.

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Originally Posted by TWR
I have no idea what size port a 7.62x39 would run but we need to know if he's having a failure to eject or failure to extract problem before we can offer ideas in the right direction.

But I have a feeling he's just screwing around.


No, I'm not screwing around, I'm waiting on a barrel nut to come in so I can properly put the barrel back on. I got my new gas block and tube last week, I just need to find the time to get everything back together and go to the range to see how it shoots. If the issue still exists, I will take pictures and post them.

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Keep us posted Hudge.
I really like the idea of uppers in that caliber.


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Originally Posted by Tyrone
Originally Posted by Hudge
Tyrone,

It’s a 16” barrel with carbine length gas tube.
Colt 6920's have a .062" gas port.

Perhaps someone here with a similar barrel that runs well could share their port size.


It doesn't work to compare gas ports for different cartridges and expect them to match. You're talking about a 5.56 barrel, he has a 7.62x39.

I don't know why everybody's talking about drilling gas ports anyway; nothing in Hudge's comments indicates the rifle is undergassed.

Hudge, I asked in post #5 in this thread about the type of failure, and you answered in post #8 that it tries to feed a new round while the fired case stays in the bolt. That's a bolt problem, not a barrel problem. You've got issues with either the bolt itself, the extractor, or the ejector. The easy button is to try a new complete bolt, if you don't know what issues you're looking for in the bolt you have. It may be something simple though like a piece of debris jamming the ejector pin.

A dirty or rough chamber may also be an issue combined with brass forming against that better than steel, as we already discussed.

Until you address those issues or provide more info, you'll just continue to get a lot of guessing, and most of it is pretty misleading to be honest.

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Originally Posted by Hudge
Originally Posted by MontanaMarine
I must have misunderstood. I thought the spent case was staying in the chamber, or partially extracted but not ejected.

You are correct. My new gas block and tube will be here today, and I will get it back together and go one by one on the things mentioned to get it fixed.


And then he says this claiming an extraction problem and the somewhere else he says when loading one round at a time it locks back on an empty mag about half the time.

That's why I thought you were just screwing around with us, cause you've described 3 different failures.

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Originally Posted by Yondering
Originally Posted by Tyrone
Originally Posted by Hudge
Tyrone,
It’s a 16” barrel with carbine length gas tube.
Colt 6920's have a .062" gas port.

Perhaps someone here with a similar barrel that runs well could share their port size.
It doesn't work to compare gas ports for different cartridges and expect them to match. You're talking about a 5.56 barrel, he has a 7.62x39.

I don't know why everybody's talking about drilling gas ports anyway; nothing in Hudge's comments indicates the rifle is undergassed.
Exactly.
But it does provide a frame of reference. The .30's need larger ports than the .223s. However, given Hudge's .094" gas port, I think he has a problem with the gun being grossly over gassed as well. It's gotta be bigger than the Colt port, but I doubt that much bigger.

I do agree with you that it is an extraction problem with the bolt, but being perhaps grossly overgassed sure as hell doesn't help. A gun can be so overgassed as to rip off rims.

Sorry I wasn't clear on that, I don't like to speak in absolutes when I don't have experience with the exact problem presented. I much prefer to lay out breadcrumbs and let the person with the problem work their way through it.


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What needs to happen:
Put the broken rifle back together.
Take video of the malfunctions, including close up shots of the malfunction. Preferably close up slow-mo video of the action.
Everybody shut up and stop "helping" until that happens.

People are talking about what drill bits to use to waller out the poor guy's gas port, based on what size port a 20" .223 uses, when there's likely a 0% chance the home built gun's barrel, assembled by a guy who doesn't know what the parts of the gun are called, purchased to feed steel case ammo, has a gas port that's too small.


Originally Posted by SBTCO
your flippant remarks which you so adeptly sling
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Yep, 8 pages of wasted time...................started by someone w/o a clue.

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Originally Posted by Bluedreaux
What needs to happen:
Put the broken rifle back together.
Take video of the malfunctions, including close up shots of the malfunction. Preferably close up slow-mo video of the action.
Everybody shut up and stop "helping" until that happens.

People are talking about what drill bits to use to waller out the poor guy's gas port, based on what size port a 20" .223 uses, when there's likely a 0% chance the home built gun's barrel, assembled by a guy who doesn't know what the parts of the gun are called, purchased to feed steel case ammo, has a gas port that's too small.


Here is the video you requested



Originally Posted by Bricktop
Then STFU. The rest of your statement is superflous bullshit with no real bearing on this discussion other than to massage your own ego.

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Originally Posted by Hudge
Originally Posted by TWR
I have no idea what size port a 7.62x39 would run but we need to know if he's having a failure to eject or failure to extract problem before we can offer ideas in the right direction.

But I have a feeling he's just screwing around.


No, I'm not screwing around, I'm waiting on a barrel nut to come in so I can properly put the barrel back on. I got my new gas block and tube last week, I just need to find the time to get everything back together and go to the range to see how it shoots. If the issue still exists, I will take pictures and post them.


Good luck with it. I hope you get it figured out.


Originally Posted by raybass
I try to stick with the basics, they do so well. Nothing fancy mind you, just plain jane will get it done with style.
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Thanks for all that said it was an extractor problem. I ended up replacing the bolt, not the whole BCG, just the bolt and it runs like a charm.

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