AR 15 Barrel Installation

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What is one of the first resources you use when you have a question about something? The internet right? Well for this reason we like to showcase installation videos that can help you with your next build. This AR 15 barrel installation posted on YouTube by Bass Fishing Frenzy goes through the detailed steps of installing his 7.5″ VooDoo Innovation’s barrel.



“Hey guys, today I am going to be installing the barrel on my AR 15 pistol and thought I would film it for you guys.


What you will need


First things first, I am going to go over what you will need. You are going to need a vice, a 4-6″ vice will work perfect, anything smaller is not going to be able to work, anything bigger might be in the way. 4″ is what I have right here and this should work perfectly. One thing you are going to want is of course have your vice mounted as securely as you can. If there is any wobbling on it or movement at all you want to tighten that up because you don’t want any movement when you go to tighten down the barrel. You will need a torque wrench, preferably one that can go up to about 75 pounds. When it comes to the mil spec barrel nut, you can go anywhere from 35 foot pounds at minimum to maximum of 85 foot pounds of torque. So you have a large range there to adjust this barrel nut down too.


There is a lot of controversy on the wide range and what foot pounds is going to get me the best accuracy and longevity and stuff like that. It is really hard to tell because it all depends on your lower and barrel, all the different specs are relatively the same but there are very fine, minor changes within each lower and barrel so it is hard to get an exact foot pounds for best accuracy etc. So as long as you don’t go under 35 foot pounds and over 35 foot pounds your good. What happens when you go under 35 foot pounds there is going to be a little bit of play. Your not going to be able to notice it, but there will be a small amount of play where the barrel meets the receiver and what’s going to happen is when you fire the gun with the huge amounts of pressure, it will cause the barrel to shift forward and back a little bit. You don’t want this because it will mess with your headspace and accuracy etc. If you over tighten it the barrel will shift to one side causing your accuracy to be over a lot and then you having to adjust for windage a lot more than necessary. So you don’t want to over or under tighten it for those reasons.

You are going to need your torque wrench, your barrel, your receiver, your barrel nut, gas tube and gas block. You will need an armorers orous tool of some sort, or some tool that allows you to hook onto your barrel nut to tighten that down. This is a Tap Co. one. Really nice, you have multiple tools on here for castle nut, barrel nut, flash hider, beer can opener and everything on there for I think $20-$30.



Then you will need a upper receiver vice block such as this one. These two pieces here came in a kit from Wheeler Engineering, they make a lot of AR 15 parts if you have never heard of them. This tool right here is not necessary but it is very helpful. You basically put this into your upper receiver, lock down your dust cover to hold it in place and then the rod goes through your gas tube hole. What this will do is once you get your barrel nut on your barrel this will allow you to adjust your barrel nut to allow your gas tube to slide through freely. This is really nice to have, it makes it a lot easier, and simpler to make room for your gas tube but it is not really needed.

You will definitely need a vice block like this. This allows you to simply clamp your lower receiver and then clamp it into the vice and allows you to tighten down that barrel nut really solid. That’s basically all the tools you are going to need. Depending on your gas block, mine has Allen keys right there as you can see, you are going to need your Allen screws and some red Loctite to lock those down once you adjust them and everything. Then of course you will need a hammer and pin punch to put in your gas tube pin for your gas block.

Installing the barrel nut


So now what I am going to do is take my upper receiver, clamp it into the block and I have my vice over here all ready. These have rails here on this Wheeler block that allows you to set it on there like that and tighten down the block. Just get it tight enough where there is no barrel movement at all. That’s tight enough, you don’t want to warp your upper receiver. Now I am going to take some grease of some sort, the best grease for this would be some anti-seizing grease. Something you put on threads to keep from locking up when you get to a certain torque. You definitely want that if you have an aluminum barrel nut because aluminum on aluminum with high torque is going to cause those aluminum threads to seize up. Not necessary, but will help you in the long run if you ever need to take your barrel off in the future. This is just some synthetic silicone grease, but like I said it is best if you get some sort of designated anti-seizing grease for the threads. I am going to put this all over the threads and all over my extension on the barrel to make it slide easier. Rub that in a little bit. So put it all over your threads and extension and go ahead and pop your barrel into the notch on the receiver and make sure it is pushed all the way in. Then put a little more on the inside threads of the barrel nut here.


Now that everything is greased just going to slide that over the barrel, get the thread started here, and just hand tighten that. Now I am going to take my barrel nut tool and pre torque the barrel nut. What that does is pre-stretches the threads because at this point if I went ahead and tightened this down to 60 foot pounds, it would be nice and tight but over time those threads would loosen up a bit and you may in a rare circumstance loose some of that torque, just from shooting and the pressures the rifle is going to endure. I am basically going to tighten it up quite a bit, then loosen it all the way, tighten it up again, loosen it up again. Do that a couple of times and like I said that will stretch out those threads so when you go to final torque down the nut, those threads are pre-stretched and going to stay in that position permanently.


Once you do that, if you have any movement on your vice you can tighten it up a little bit more if needed to keep it from shifting on you when you go to finally tighten it. I forgot to put in my alignment tool; I will take this out of the vice real fast and put this in. Ok I have that in there and as you can see it is acting as a fake gas tube so once I get this tightened down it will allow me to easily adjust the barrel nut to wear the gas tube can slide through without any resistance.


I am going to set the torque wrench to 65 foot pounds and that way if I need to adjust it loosely or tighten it, I have a little bit of room to play with to keep it in the safe zone. Then go ahead and take your armorers orers wrench and of course all of the armorers ors wrench will have the little insert that will allow you to stick your wrench into. Double check and make sure it is at the right torque which it is. Get the notches lined up which can be the trickiest part sometimes. This is a long video but I wanted you guys to see everything without making multiple videos. Now we are just going to tighten her down. So there is 65 foot pounds right there and then I am going to take my little adjustment tool and see where I am at. I am actually just about perfect, now that is luck. It is going to need to be tightened just a little bit. I will quickly adjust this just a little bit more. Finding that notch is a pain. There we go.


Now once you get that adjusted you can go ahead a line up your gas block and put in your gas tube pin into the gas block and you are basically done once you get that set up. Let me get everything organized here and I will show you guys how to put on that gas block.

Checking headspace


One thing I wanted to go over real fast before I go into the gas tube installation is headspace and checking to make sure your rifle is safe after barrel installation. A lot of people are scared about headspace issues, some people say you have to check your headspace after you put on a barrel and some say you really don’t have to. I am one of those people who think it’s really not that big of a deal but at the same time, you should get it checked at some point to make sure it is safe. The easiest way to do that and the most reliable way is to take a bolt carrier group (BCG) like this standard mil spec BCG nothing special. Slide that into your receiver after you get the barrel tightened down to the correct torque and everything. What you want to do is take a quick look at the back of the receiver here and as you can see the BCG is flush with the receiver and that is what you are looking for. If your bolt is sticking out like that, that is very bad, you don’t want that and you are going to blow up your face and your gun when you pull the trigger. First off it probably wouldn’t function and feed but if it were to this would be a big problem and you would have a face full of shrapnel. So what you are looking for is the bolt to either be directly level or tad below the surface of the receiver like this is. That’s what you are looking for and as long as you see that you are pretty much safe.

You can buy some no-go and go gauges. They are shaped like a cartridge and you drop them into your chamber and if the no-go gauge sticks out that’s good if the go gauge is completely flush your good. they are about $60 each so kind of expensive. My recommendation if you are only building a single rifle and your not going to be building more in the future after you get it done just drop it by your local gun smith and ask him if he will drop in a couple of gauges and check it and he will probably charge you like $20. For the piece of mind that you could get if you feel really uncomfortably with it then just do that. As long as your BCG is seated properly like that, you’re not going to have an explosion and you’ll be fine. So just wanted to go over that real fast because a lot of people are concerned about headspace. They think it is a must and sometimes it is but the majority of the time as long as you stick your bolt in there you’re basically safe

Installing the gas block


Now we will throw this back in the vice and get this gas tube on. What you want to do if you haven’t yet is install your roll pin for your gas block and gas tube. Just drive in the pin with a punch and hammer or pliers, whatever your have. It is really not that hard to do.


One thing you do want to look at though is if you have a gas tube and a gas block from a different company (really rare circumstance because SAMMI makes sure the specs are the same on everything so it won’t happen often) you want to look carefully in there and see the hole of the gas block meeting the hole in the gas tube. Like I said in rare circumstances sometimes the hold in the gas tube and the hole in the gas block won’t line up correctly and what would happen is maybe half that hole would be covered by the gas block and that would cause an insufficient amount of gas being transported back through the gas tube and pushing your bolt back. If that happens you will have reliability issues and stuff like that. So just take a look down at that hole to make sure you can see all of the gas tube hole there to allow you to get the most amount of gas pressure going back through and the most reliability. This is of course a pistol length system here, but I am actually using a pig tail gas tube. This fits a pistol length system, but with this curly tube at the end if you were to stretch it out it would be rifle length. So if you had a pistol length gas tube and maybe half that hole is covered up that would be ok because there is so much more pressure and gas with a pistol length than say a rifle or mid length. If you have a rifle or mid length and half the hole was covered you may run into issues, so it’s not a big problem but something you want to look out for.


Now what I am going to do is slide on my gas block and my gas tube, this is a very tight gas tube because that curly cue rides up on the barrel so I have to do some pushing and shoving to get it on there correctly. Once I get this set up I will get back to you guys and show you how to put in the set screws.

Just slide on the gas block. Slide that on and get it roughly aligned with the top of the receiver and what I am going to do now is just eyeball it, adjust that until it is as straight up and down as I can get it. Just eyeball it and get it as straight as you can and make sure your gas tube is not under tremendous stress. Depending on your barrel, and your gas block, and your gas tube and receiver it may be a tight fit. Don’t be scared to push everything. If you need to use a rubber mallet to tap on the gas block that is fine. Just keep an eye on the gas tube to make sure it is not bending or under any stress. Everything looks to be straight and all good, so now I am going to put some red Loctite on the set screws for the gas block and go ahead and clamp those down and we will be basically done.



One quick thing to note about Loctite is to make sure you are using red Loctite. If you use blue Loctite what will end up happening is once a barrel gets up to a certain temperature from shooting, it will actually melt the blue Loctite and then it will basically not have any thread locker left on your screws. So make sure you are using red Loctite, it may even come loose with red Loctite it depends on how many rounds you shoot at one time, it can heat up your barrel pretty hot. So it may even melt the red Loctite but the red is set for a higher temperature so it is safer to use red. That is one downfall of most low profile gas blocks is that they do use set screws. If you have owned an AR with an A frame front site post you’ll notice that the pins go horizontally through the barrel which basically removes any movement within the front site. I wish all low profile blocks had is the pin system those have. As long as you tighten these down and put a generous amount of Loctite on there it should stay solid. That may be something you want to do after every thousand rounds or so; check the gas block, gas tube pin and an overall systems check to make sure everything is still tightened and hasn’t moved.


Once you get that gas block tightened down you guys are done. Just throw in your BCG, flash hider, and handguard and basically you have a complete upper.”


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