Lets discuss AR-15 gas block installation techniques

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    DAVE_M

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    If you're planning to dimple the barrel, a dedicated jig is certainly the way to go. Using the gas block as a jig is a horrible idea. First of all, the dedicated jig lines itself up on the gas port to make sure the dimple is in the right spot. Secondly, putting a spinning bit into the screw hole of a gas block greatly increases the chances of ruining the threads on the gas block. And you're not saving any time. It's the same number of steps each way bit the jig saves you a few minutes. You lock the gas block or jig to the barrel. With the jig, the screw automatically centers itself on the gas port. With the gas block, you have to guess and then clamp the gas block down or take more time to ensure the gas block is in the exact right position. After you drill the dimple, you have to remove the jig or gas block to clean up the shavings. At that point, you might as well have used the jig.

    That’s the main issue with not using a jig. They have no means of confirming alignment of the port and block, but also have no way to locate where the dimple should be. Using the gas block as a template is a bad idea, because again, there is no way to accurately locate the dimple location. I’ve seen multiple examples of dimpled barrels done improperly. A bore scope is inserted and can show the block is misaligned. Best way to do it is by locating the gas port and drilling a dimple opposite of it. That simply can’t be done accurately using this gas block as a template.
     

    Magdump

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    So you use a bit much smaller than the hole in the gas block and hope the dimple is nice and centered so the gas block is correctly oriented with the gas port?
    I clamp the barrel in the vise with barrel blocks and get a bit centered and start the hole. Remove the block and drill the dimple. I don’t always do it like that but I’ve done it more than enough times to feel comfortable doing it that way and by some miracle it always seems to work out. Go figure. Other times I dig out the jig and use that. Somehow, same end result. If I hadn’t done it so many times I might take stock in someone’s advice telling me it’s a really bad idea, but it’s too late for me to buy that. I guess all the people who’ve brought me half built or broken rifles to fix for them just hope I’m able to make things right, and again, by some chance I wind up getting it right just pissing in the wind...
    It’s entertaining to read all these posts from expert builders with a degree in rocket science talking about the only way to assemble the AR15. Again, if I hadn’t successfully built so many over the past near 40 years I might doubt myself.
     
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    thperez1972

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    I clamp the barrel in the vise with barrel blocks and get a bit centered and start the hole. Remove the block and drill the dimple. I don’t always do it like that but I’ve done it more than enough times to feel comfortable doing it that way and by some miracle it always seems to work out. Go figure. Other times I dig out the jig and use that. Somehow, same end result. If I hadn’t done it so many times I might take stock in someone’s advice telling me it’s a really bad idea, but it’s too late for me to buy that. I guess all the people who’ve brought me half built or broken rifles to fix for them just hope I’m able to make things right, and again, by some chance I wind up getting it right just pissing in the wind...
    It’s entertaining to read all these posts from expert builders with a degree in rocket science talking about the only way to assemble the AR15. Again, if I hadn’t successfully built so many over the past near 40 years I might doubt myself.

    There's a bit of uncertainty in your method. Hopefully the gas block is oriented correctly with the gas block when the gas block is clamped down. Hopefully the bit is centered when you start the hole. If you've never had an issue with it, good on you. Just because it's worked out so far does not mean it's good advice. Especially when you have a tool, the jig, that is designed to eliminate the sources of uncertainty in your method. That would be like me moving a hammer to grab a 15 inch adjustable wrench to hammer in some nails. Sure, it might get the job done and I might have never had any issues with that method but I doubt anyone would suggest the wrench over a hammer when both are available. Out of morbid curiosity, if you have the jig, why do you use the gas block? Can you at least see how, from an engineering point of view, the jig is more precise?
     

    Magdump

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    There's a bit of uncertainty in your method. Hopefully the gas block is oriented correctly with the gas block when the gas block is clamped down. Hopefully the bit is centered when you start the hole. If you've never had an issue with it, good on you. Just because it's worked out so far does not mean it's good advice. Especially when you have a tool, the jig, that is designed to eliminate the sources of uncertainty in your method. That would be like me moving a hammer to grab a 15 inch adjustable wrench to hammer in some nails. Sure, it might get the job done and I might have never had any issues with that method but I doubt anyone would suggest the wrench over a hammer when both are available. Out of morbid curiosity, if you have the jig, why do you use the gas block? Can you at least see how, from an engineering point of view, the jig is more precise?
    You mean gas block is oriented with the gas port? Don’t worry, I’m not going to discount your entire post over a small mistake because I’ll admit I knew what you meant.
    Yeah Perez, I can see how it’s more precise. I’m not telling anyone they should avoid a jig. Just sharing what has worked fine for me. I even offered the use of mine. Can you at least see that there’s a huge difference in the size of any gas port on any AR barrel and the opening on the gas block? Any idea the diameter range on AR15 gas ports for different barrel lengths? Do you think a couple of thousandths of an inch from center of the hole in the gas block is gonna make or break the build? Try this, next time you pull a FSB that’s pinned to the barrel, inspect the barrel at the gas port. Look specifically for the carbon mark around the gas port and decide whether the gas port was exactly centered under the hole in the gas block. The majority that I have seen are not (wonder how thick a handguard cap is?). It’s not at all a challenge for me to get at least that close. If someone wanted to dimple the barrel and didn’t have a jig, they could easily and successfully do so by using the steel gas block without damaging the threads. I’ve completely drilled stainless screws from aluminum parts without damaging the threads in the least. It was not a challenge. There are pics of the procedure that I posted on this site. If you like, the next time I dimple a barrel I’ll take step be step pics and post them for you.
    Btw, you don’t have to be an engineer to assemble an AR. I’m not even a mechanic. I’m just mechanically inclined.



    https://www.bayoushooter.com/forums/showthread.php?163317-How-the-H-E-double-L-!!&highlight=
     
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    thperez1972

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    Yeah Perez, I can see how it’s more precise. Can you at least see that there’s a huge difference in the size of any gas port on any AR barrel and the opening on the gas block? Do you think a couple of thousandths of an inch is gonna make or break the build? Try this, next time you pull a FSB that’s pinned to the barrel, inspect the barrel at the gas port. Look specifically for the carbon mark around the gas port and decide whether the gas port was exactly centered under the hole in the gas block. The majority that I have seen are not. It’s not at all a challenge for me to get at least that close. If someone wanted to dimple the barrel and didn’t have a jig, they could easily and successfully do so by using the steel gas block without damaging the threads. I’ve drilled stainless screws from aluminum parts without damaging the threads in the least. It was not a challenge. There are pics of the procedure that I posted on this site. If you like, the next time I dimple a barrel I’ll take step be step pics and post them for you.

    Yes, there is a size difference. I just don't see that as an excuse for sloppy work when the right tool is right there. But putting that issue aside, the jig is simply easier to use. There's no having to eyeball the orientation or use air to make sure it's lined up. The aligning screw does all that for you. And it's designed to hold the bit centered while the jig is attached. In every aspect of the task, lining up, starting the dimple, and drilling the dimple, the jig is easier and more precise. There are literally no advantages to using the gas block over a jig. So if someone has both, I cannot think of any reason to use the wrong tool for the job.

    I have no illusions that anything I say would ever change your mind. You are your 40 years of experience are going to do what you're going to do. But if you publicly suggest a horrible idea to someone looking for advice, expect for the advice to get questioned. You've offered nothing to show using the gas block over the jig is better or even on par. You've only indicated that your using the wrong tool has so far resulted in acceptable outcomes.
     

    Magdump

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    Yes, there is a size difference. I just don't see that as an excuse for sloppy work when the right tool is right there. But putting that issue aside, the jig is simply easier to use. There's no having to eyeball the orientation or use air to make sure it's lined up. The aligning screw does all that for you. And it's designed to hold the bit centered while the jig is attached. In every aspect of the task, lining up, starting the dimple, and drilling the dimple, the jig is easier and more precise. There are literally no advantages to using the gas block over a jig. So if someone has both, I cannot think of any reason to use the wrong tool for the job.

    I have no illusions that anything I say would ever change your mind. You are your 40 years of experience are going to do what you're going to do. But if you publicly suggest a horrible idea to someone looking for advice, expect for the advice to get questioned. You've offered nothing to show using the gas block over the jig is better or even on par. You've only indicated that your using the wrong tool has so far resulted in acceptable outcomes.

    I’m laughing at your post. You take this way way way too serious.
    I did not condone using a gas block in place of a jig. I simply said if you don’t have a jig, you can use a gas block. I also never said it was better to use a gas block. But there you go. And you can. Yes you can. But keep up the vigil good knight. Don’t allow any horrible advice to seep through the cracks and sabotage someone’s build.
    Because without all you internet hero types out there this world would likely crash.
     

    MOTOR51

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    Who besides me saw this train wreck coming? Build the rifle however you want, who cares. OP, obviously there are a few different ways to do most things, take it to an actual armorer if you want to avoid 20 pages over the next 2 weeks of arguing back and forth. Or just google it, that’s where most of the internet advice on gun forums comes from anyhow


    Sent from my iPhone using Tapatalk Pro
     

    Magdump

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    Who besides me saw this train wreck coming? Build the rifle however you want, who cares. OP, obviously there are a few different ways to do most things, take it to an actual armorer if you want to avoid 20 pages over the next 2 weeks of arguing back and forth. Or just google it, that’s where most of the internet advice on gun forums comes from anyhow


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    You’re absolutely right Motor. On all counts. Night all.
     

    thperez1972

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    I’m laughing at your post. You take this way way way too serious.
    I did not condone using a gas block in place of a jig. I simply said if you don’t have a jig, you can use a gas block. I also never said it was better to use a gas block. But there you go. And you can. Yes you can. But keep up the vigil good knight. Don’t allow any horrible advice to seep through the cracks and sabotage someone’s build.
    Because without all you internet hero types out there this world would likely crash.

    Well...yeah.

    Who besides me saw this train wreck coming? Build the rifle however you want, who cares. OP, obviously there are a few different ways to do most things, take it to an actual armorer if you want to avoid 20 pages over the next 2 weeks of arguing back and forth. Or just google it, that’s where most of the internet advice on gun forums comes from anyhow

    There's no train wreck here yet. At least not in this thread.
     

    John_

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    Who besides me saw this train wreck coming? Build the rifle however you want, who cares. OP, obviously there are a few different ways to do most things, take it to an actual armorer if you want to avoid 20 pages over the next 2 weeks of arguing back and forth. Or just google it, that’s where most of the internet advice on gun forums comes from anyhow

    There is a lot of good info being shared here and I knew we have a few guys who are really knowledgeable on the topic. Your suggestion is like saying "lets not have any discussion because its just gonna go to **** show" which is a pretty foolish comment on a discussion forum. You can best believe others here are, or will learn from this thread going forward.

    I actually had thought (before I started this thread) of removing the one setscrew (180 from gas port) from my functioning GB and center punching the barrel if my thinnest punch will fit thru the hole. Or maybe the setscrew has made a visible mark already on the barrel (very likely). When I assembled it to the barrel, I did my best to align it visually, and used an .020 feeler gauge off the barrel shoulder (so many people just butt it right up to barrel shoulder and that is not correct) but in the end, it is probably a couple degrees off rotation eyeballing it after with the handguard installed for a better visual reference. It ran fine for its first 40 rounds, not a single issue, but clearly using a precision jig to dimple the barrel is superior in every respect.

    I bet a lot of assemblers here just push the GB up against the shoulder of the barrel, visually align the GB to the barrel, and tighten the setscrews. And that is not the correct way to install a low profile GB, clamp on or set screw unit. Evidently the PSA assemblers do the same because upon close inspection of my 300 BO upper there is no gap between the GB and barrel shoulder. But it still runs fine so far. Like Mag alluded to above, some slight misalignment is tolerable/workable. But if you had your choice in the matter, would you choose misalignment vs correct alignment?

    You only get one shot to dimple the barrel accurately. Me personally, I prefer accuracy to "well it might work right". The 18" FN chrome lined barrel cost me $210, and that was on sale. FN America produces a very high quality barrel, and they have been doing so for over 100 years.
     
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    103M 95G

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    Buy the tool. Use A good quality drill bit. 8AD682F5-C6E7-4BE9-AAE5-9F790D65B2F4.jpeg
     

    ozarkpugs

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    You mean gas block is oriented with the gas port? Don’t worry, I’m not going to discount your entire post over a small mistake because I’ll admit I knew what you meant.
    Yeah Perez, I can see how it’s more precise. I’m not telling anyone they should avoid a jig. Just sharing what has worked fine for me. I even offered the use of mine. Can you at least see that there’s a huge difference in the size of any gas port on any AR barrel and the opening on the gas block? Any idea the diameter range on AR15 gas ports for different barrel lengths? Do you think a couple of thousandths of an inch from center of the hole in the gas block is gonna make or break the build? Try this, next time you pull a FSB that’s pinned to the barrel, inspect the barrel at the gas port. Look specifically for the carbon mark around the gas port and decide whether the gas port was exactly centered under the hole in the gas block. The majority that I have seen are not (wonder how thick a handguard cap is?). It’s not at all a challenge for me to get at least that close. If someone wanted to dimple the barrel and didn’t have a jig, they could easily and successfully do so by using the steel gas block without damaging the threads. I’ve completely drilled stainless screws from aluminum parts without damaging the threads in the least. It was not a challenge. There are pics of the procedure that I posted on this site. If you like, the next time I dimple a barrel I’ll take step be step pics and post them for you.
    Btw, you don’t have to be an engineer to assemble an AR. I’m not even a mechanic. I’m just mechanically inclined.



    https://www.bayoushooter.com/forums/showthread.php?163317-How-the-H-E-double-L-!!&highlight=
    When the shtf and the internet is down and the sexual intellectuals can't help them build an AR from parts because the appropriate tools are non available who are the people going to go to ? The smart ones will say " AR s are simple pieces of machinery " and seek out mechanically inclined people . People who can use a rail road spike and assortment of nails ,and a file to cobble together a working gun from a pile of parts if need be . I'm sure Mag will be pretty buisy .

    Sent from my moto g(7) play using Tapatalk
     

    John_

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    ↑ words of wisdom and snarky remarks from the retired auto mechanic. The guy who advocates sealing your GB with a liberal application of blue loctite when you assemble it.

    Oh brother.....
     

    thperez1972

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    When the shtf and the internet is down and the sexual intellectuals can't help them build an AR from parts because the appropriate tools are non available who are the people going to go to ? The smart ones will say " AR s are simple pieces of machinery " and seek out mechanically inclined people . People who can use a rail road spike and assortment of nails ,and a file to cobble together a working gun from a pile of parts if need be . I'm sure Mag will be pretty buisy .

    Sent from my moto g(7) play using Tapatalk

    It's an illogical conclusion to say those who know how to use and prefer to use the appropriate tools would not be able to build an ar from parts if those tools are not available. You conclusion is based on those people not knowing how to do the field expedient method when the opposite would be more likely. Because they know the reasons for using the right tools, they are usually better able to adapt to not having the tools.
     

    ozarkpugs

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    ↑ words of wisdom and snarky remarks from the retired auto mechanic. The guy who advocates sealing your GB with a liberal application of blue loctite when you assemble it.

    Oh brother.....
    Please copy and paste where I advocated liberal use of blue loc-tite . And you can suck up all you want but you are the one who said building an AR lower was a piece of cake then when your sexual intellectual buddy started talking about people who referred to people who were ignorant enough to compare AR building to cakes instead of defending your statement you jumped on me to take the light off yourself . And for your information if you get the barrel hot enough to transfer enough heat to the block to melt even blue must less red loctie you will have more problems than a knurled screw vibrating loose.

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    JR1572

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    Nothing better than reading improperly assembled sentences about how to properly assemble a firearm.

    103M95G, I would ask to use the tool to assemble an upper, however I’m not a certified WECSOG armorer. Thanks for the offer though...
     

    ozarkpugs

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    It's an illogical conclusion to say those who know how to use and prefer to use the appropriate tools would not be able to build an ar from parts if those tools are not available. You conclusion is based on those people not knowing how to do the field expedient method when the opposite would be more likely. Because they know the reasons for using the right tools, they are usually better able to adapt to not having the tools.
    If they knew as much as they like to pretend to they would not be blowing their horns and knocking everyone's opinion as junk if it is not the same as their opinion . If you do not recognize an AR as a loose tolerance piece of machinery you are not very educated on ARs . No one is suggesting it is not best to use the right tools , one member who was criticized for describing an alternate way to dimple a barrel offered to loan his proper tool . I never said anything about not building an AR or anything else half a&& I said you don't have to be a pompas sexual intellectual to do it right .

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