Atlas/PZ Build Kit - Dos and Dont’s of Barrel Fitting

Added: 2026-05-18

[00:00:04]What's up YouTube? We're back here today and as you can see a very different scenario. That's because I am traveling.

[00:00:10]Uh I'm traveling for work. So um you know I actually found a match where I am. So I brought the 4.6 in build with me. And that's because first of all I know it works but I want to make sure that you know everything is working as intended. gun is accurate and I can go through a match without any problems, which should be fine, like should happen. And then it was also a good opportunity to, you know, just sit down here and talk to you guys. Um, I know a lot of you asked about the barrel feeding process. And even though I was recording everything, uh, like as you can see on the channel, I already put the ejector in there. The thumb safety uh, video is in there, everything is in there. um showing you how to put the whole kit together. The critical part is the barrels. So, I started recording, but the barrel took me, I'm not kidding, over 6 hours to get fitted. And I'm going to go over like all the details here with you guys right now. Uh and tell you, um you know, what you should expect if you're trying to fit a barrel by yourself. So before we start, you should know that uh even though we're not using a mill, uh we're using a couple of specialized tools and they are a lower lug cutter, uh a barrel alignment block, and a barrel holder.

[00:01:35]These three you can purchase at Brown Nails. And uh I'll try to pin a comment down below here with the link for each one of them. I think those are essential for you to fit a barrel. um at least fit it accurately. Um and I will explain why. So, let's start by saying how you fit a barrel. So, here is my barrel.

[00:01:57]Here's I took the gun apart before the video started. And when you get the barrel, when you get the gun, the kit, uh when you slide the barrel in, it gets to about here on the hood and it stops just like this. So, what you need to do is file the sides this. So, let me see if I can show this to you guys. You got to file this side and then this side of the hood. So, the width of the hood is equals the width of the brereech face.

[00:02:33]But you got to make sure that this barrel is aligned because if you file too much on one side or the other, you end up with like a barrel that is going to be twisted and that's not what you want. So once you do this, then you're going to start sliding your barrel in until it locks in place. So let me see if I can show you guys. But here's the barrel and it's kind of like down there and it locks in place like this. So it goes all the way to the back and then to the top and it locks in place. So for this to happen then you have to start filing the barrel the hood length which is this surface right here. And um this is what I did wrong on my first barrel because I started filing the sides of the hood and then when I slid the barrel into the the slide, it would go but not all the way down. So it would not lock in place like this one is locking. So I thought, okay, my hood length is too long. And I started filing the hood length. But it was actually because since I'm doing everything by hand, it is extremely hard to file this surface square and flat. So I ended up filing it in a little bit of an angle. So it was something like this. So it would slide in and then bind on the sides. And I thought it was binding on the hood. So, I ended up like filing the hood. Uh, and when I figured that it was the sides, I then, you know, made them square, it got in, but it had a little bit of a gap, a futile uh on the hood length. And because of that, I had to then work on the the top the the top lugs and then uh by that point, you know, the barrel was was shot. So, um, if you're doing this, make sure that when you're filing the sides of your hood, uh, make sure that they are square, they are flat before you even start doing anything to your hood length. Uh, the hood length, um, I don't have the measurement by the top of my head here, but I I think it's like 1.315 in is what you're looking for for Atlas.

[00:05:10]uh slides. They're all pretty much going to be in that range, plus or minus a towel. And I think like the most important advice that I can do, and that's why it took me like six plus hours to fit this barrel, is go slow.

[00:05:26]So, take one stroke with the file and then try it and then measure. And then if you need more, take another stroke and then go and measure. And keep doing this until you get a hard fit. So that's what I got with my barrel. It was like a hard fit. So it would go in and then had some resistance going into like battery and everything. So uh and even like locking up. Um so that's that's kind of like what you want because you don't want a barrel that is going to be too loose in there. Um and then after that I just started like literally like just sanding a little bit like you know polishing a little bit to make sure that it was like smooth. So, this is how you go and you fit your uh barrel hood.

[00:06:12]Start by the sides. Uh, and here is my advice. Go to Engineers Armory on YouTube. That guy is a master. Um, and him and Chem Firearms, both of them were like, you know, heavily involved in uh my fitting of this barrel. Jaden from Cam Firearms. Uh he was like with me on uh on a you know messages all the time because I I would have a question reach out to him and he would he would say like do this, do that. And then uh Engineers Armory um his videos are extremely informative. Like if you if you follow it step by step uh his you know barrel fitting uh guide uh you will for sure be able to fit a barrel. And that's what I did. So, after you get your barrel hood fitted, everything is squared, everything is is is good, and your barrel locks in place. So, you're going to have something like this that you put it up there, it locks in place. And now you need to address your uh lower lugs. And this is where the brown nail's lower lug cutter gets important because um as you guys can see I don't know if I can show but you have like a very nice cut there very nice radius and that's done with uh with the lower lug cutter because like essentially what it does is it goes through your frame here where your uh slide stop is going and it you just like turn a lever and that starts starts cutting the lower lugs uh on the exact same uh radius that you need. It's just a little bit less than what you need. And then you just finish with like a sandpaper uh and a three I think it's a 3/16 uh pin punch. So you just like wrap the the the sandpaper on that punch and then you just like starting start sanding everything so you get like a smooth u and beautiful surface. And I have mine kind of still marked in there, but you can see the shiny spots. That's where the the the link, not the link, but the the slide stop is sitting. So, it's it's getting like an even uh wear on both sides, which I'm pretty happy with. You can try to do this by hand with like a a round file or something, but I highly advise you not to. Um I think you're going to pay like you're probably going to spend 200 bucks in specialized tools, but they can be used for like many many builds. So, this is how I fit the barrel for the 4.6. That's why it took me six plus hours to fit this barrel because I went really really slow. Um, measured three times before I filed again. Uh, so like remember it's easier to uh remove material than to add material. So goes slow, have patience and follow the steps on the engineers armory uh video. All the measurements, the barrel hood formula, everything is going to help you to get this fitted uh precisely.

[00:09:33]So here is with the barrel fitted. And as you guys can see, very smooth.

[00:09:45]Goes down, locks up. All right. So, that's how it's done. If you uh if you think it's a little too much, it looks like Perfect Hero Atlas, they are releasing the 5 in.

[00:09:59]So, the the latest upgrade to the 5-in build uh build kit was that the the barrel was actually an easy fit. Uh and it looks like the hood comes already pre fitted. So, it's already cut for uh the barrel to lock up in place. The only thing left is to cut the lower lugs. So, um, you know, that's an easier task in my opinion because you're using the lower lug cutter and, uh, you don't need to be as precise with the file, for example. And you can check it out on Tactical Bearded Dad. U, I'll leave a link in the description below for his channel. He is doing a 5-in kit uh, that came with a pre fit barrel. So, go and check it out.