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How To Build An AR-15 Rifle – The Ultimate Guide To What You Need for Your AR

So you want to build an AR-15? Well it’s not as daunting as you might think. The AR-15 is almost without a doubt the most easily configurable rifle platform on Earth. That doesn’t mean that it’s hard to put one together though.

So the AR-15 isn’t exactly what the military carries but it’s pretty darn close. The AR-15 is now what is considered the most popular civilian sporting rifle. While it’s a far cry from the fully automatic, grenade-launching assault rifle the Marines carry, it’s a great rifle capable of incredible accuracy and precision at great distances. Plus it’s a hell of a lot of fun to shoot.

how to build an ar-15

If this will be your first AR-15, then you’ve come to the right place. We’re going to go over everything you need to know about building an AR-15 of your own including what parts you’ll need, what tools you’ll need, what accessories you should consider and how to put it all together into an awesome custom AR rifle that you’ll cherish for decades.

So if you’re interested in building an AR, keep on reading!

How You’re Going to Build Your AR

First things first, you need to decide on how you’re going to put this thing together. There are several options and they really depend on just how much time and patience you have.

Buying a Completed Upper and Lower

Probably the easiest way to build an AR, whether it’s an AR-15, AR-10 or even a 9mm AR is to buy a completed and pre-assembled lower receiver and upper receiver separately and just put them together.

This method is very straightforward and simple. You buy a completed lower receiver, either online or through your local gun shop. A completed AR lower receiver includes everything you need already assembled. That includes a butt stock, grip, trigger assembly, buffer spring, safety selector switch and various other small parts. In most cases, you will need to have your completed lower shipped to your FFL (if you ordered online) or be subject to a waiting period at your local gun shop.

Then comes the upper receiver. Again you can buy it online or at a local gun shop and there are a TON of different ways you can go with this. Completed uppers have everything you need to mate them to a completed lower to make a functioning rifle. That includes the bolt carrier group (not all completed uppers come with this essential part), charging handle, upper receiver assembly, dust cover, barrel, handguard and some even come with iron sights. Unlike a lower receiver, you can have an upper receiver shipped right to your door in most states.

Buying a completed upper and lower is very simple and once you have the two parts along with a charging hand and bold carrier group, you’ll be good to go.

Building Your AR Completely from Scratch

So what do I mean when I say “from scratch”? Well, it can get as complicated or as simple as you want it to be. You can mix and match all of the components of your AR-15, making it completely custom. Going this route also means that you are going to learn about every piece and part of your AR-15 and how it works intimately. It’s definitely not the easiest route to take and we definitely don’t recommend doing this for your first AR-15 build but the option is there.

First you’ll buy a lower receiver that is stripped, that means that it’s just the metal piece without any of the goodies like a butt stock, trigger, buffer spring, etc. Buying a stripped lower receiver these days (2017) costs about $50.

We recommend buying a parts kit complete with trigger assembly and all the other goodies to complete your lower receiver (apart from the butt stock) for around another $50.

Next is a stripped upper receiver. These will run about another $50 but you’ll be spending a bit more money to complete your upper than you did your lower. The reason for that is because the hand guard and barrel are going to cost you. A decent barrel will go for around $120 and a hand guard can cost as much as $200.

This is the point where many prospective AR-15 builders say, “Screw it, I’m buying a completed upper and lower.” We’re going to tell you right now that’s not a bad idea at all.

If you are dead set on continuing on building your AR from scratch then you’re going to need some tools to do it.

Here’s the short list of tools you’ll need to build your AR-15 from scratch:

  • AR-15 Armorer’s Wrench
  • Roll pin punch set
  • A set of allen keys
  • AR vise tool

There can be more tools that you’ll need but the ones listed above are essential to any AR build project.

The Main Components of Any AR-15: The Upper and Lower Receivers

I always like to think of any AR rifle as somewhat of a “Lego” gun. That’s because there are so many things you can put on these rifles to suit your needs. In fact, the upper and lower are held together by two pins making this essentially a 2-part gun.

Generally speaking, the upper receiver is taking the lion’s share of abuse after a range visit. The bolt carrier group is moving back and forth and getting dirty. The barrel is subjected to some extreme heat and is getting worn down slowly by the ammo you’re shooting. Meanwhile, the only sexy part of the lower receiver is really the trigger.

Both the upper and lower are working together to give you a reliable firearm that you can depend on to shoot consistently time and time again.

Lower Receivers

Let’s talk about lower receivers. The lower on any AR-15 basically consists of the buttstock, the trigger group and the grip. Those are the things you mainly have to worry about.

When buying a lower receiver, stay with a metal one and avoid the polymer lowers that are out there. They’re just not strong enough to take the abuse and remain consistent like a nice billet lower will be.

Spend More on the Upper Than Your Lower: Here’s Why

If you’re on a budget, we’d advise you to splurge more on the upper than you would on the lower. The reasoning is because you want to make sure that you’re going to have a reliable and accurate rifle.

Many stripped lowers can be had for under $70. They’re all high-quality and essentially work the same way. Now if you’re buying a completed lower, you’ve also got some options in terms of what kind of furniture comes with it. In many cases, it is more cost effective to buy a completed lower than put it together yourself.

If you are going to be piecing together the lower yourself, consider that you need to tack on at least another $50 for a good quality lower parts kit.

AR-15 Upper Receivers – Build or Buy a Completed AR Upper?

As with lower receivers, you have to decide whether to build your upper part by part yourself or just go out and buy a completed upper. More often than not, you’ll be spending more money doing it yourself vs. buying a quality completed upper.

Similar to lower receivers, you’ll also need to buy a parts kit for your stripped upper receiver if you choose to do it yourself. Also figure in the cost of a barrel, hand guard and other essentials to put it together yourself.

A quality AR-15 completed upper will run you a minimum of $400.

AR Uppers – What to Look For Based on Your Intended Usage

Lots of folks ask us what they should look for in a completed upper. It really depends on what you’re going to use the rifle for.

If you want a range toy that can do everything from 50yds to 500yds, consider a full length gas system on an 18″ barrel. Throw on a good 1-4x scope and you’ll be smiling ear to ear.

More of a CQB guy? Try a carbine length gas system on a 16″ barrel. Pop a solid Aimpoint on there and you’ll be in heaven.

Will your AR be a duty gun? Forget about “budget” components because you should be spending no less than $1,200 on a quality Colt or Daniel Defense AR that has already been assembled at the factory. Your life depends on the reliability of the gun so we would advise not to build your own in that case.

AR-15 Optics – From Red Dots to Scopes

Here are our recommendations for AR optics based on what you’ll be using the gun for:

Red Dot Sights

These are great for CQB (close quarters battle) type rifles that are going to get a lot of use up close. If this is your duty gun, go for an Aimpoint. If this is a range toy, check out Bushnell’s TRS-25 or one of the Vortex RDS that we reviewed here.

Red dot sights on AR-15’s are flat out a blast to shoot and the fast target acquisition is awesome. Much better than iron sights, plus they look cool while being functional.

Variable Zoom Scopes

It’s hard to beat a good 1-4x or 1-6x scope on an AR, especially if this is going to be your all-around range toy. The variable zoom will allow you to use scopes like these similarly to how you would use a red dot sight, while still giving you the option to zoom in and shoot at ranges exceeding 300 yards.

Variable zoom scopes are our recommendation for people that are building a budget AR as well as others looking for a SHTF gun because of their cost effectiveness and versatility.

Iron Sights

We believe every AR should not go without a set of backup iron sights. If your life depends on your gun working, you absolutely must have iron sights on your AR-15. Even if you’re at the range and the battery on your red dot goes out, you still should have iron sights mounted on the gun.

Laser Sights for AR-15: What You Should Know

If you’re looking for laser sights for your AR-15, you’ve come to the best place on the internet. We won’t go into too much detail on what laser sights you should get for your AR or what you should look for here because we already wrote the best resource on the planet here about AR lasers.

Here’s a quick rundown just for fun though:

Green lasers are best suited for AR-15 rifles because they are much easier to see than red lasers in both nighttime and daylight conditions. Also, you should be looking for an easy to use laser sight that either has a momentary switch or a very easy method of activation.

Lastly, you should be putting some serious consideration into laser and light combos for your AR build. Those are best suited for home defense AR-15 rifles as well as any purpose-built AR that will be used indoors.

AR-15 Lights: An Essential AR Accessory for Home Defense

In addition to a quality laser, you need to be thinking about a white light for your home defense AR-15.

There’s a lot of options out there, but you just can’t go wrong with anything built by Streamlight. Also think about a laser/light combo, many of which are of super-high quality and are reasonably affordable.

If this is going to be going on your home defense gun, stop thinking about cheap Chinese lights and start thinking about rugged flashlights that are going to turn on every time. Also consider lights with multiple modes like strobe and stronger/weaker light modes.

We wrote a great post on AR lights here if you were interested in reading more.

AR Magazines – Plastic or Metal?

In this day and age of PMags, you really don’t have to be dead set on metal magazines anymore. A set of 5 or more PMags will last you longer than the rifle’s useful life. Of course, there are lots of guys that have sworn their lives to using metal magazines in their AR-15’s and that’s cool too.

If you’re new to the AR platform, be sure to buy a few 30 rounders as well as 10 rounders for bench shooting.

The Best Ammo for Your AR-15 – Brass vs. Steel Case

If you’re looking for the best type of ammo for your AR, then brass cased ammo is the hands down winner. There’s just no doubt that brass shoots cleaner, ejects and chambers better and it will beat up your gun a lot less than steel cased Tulammo or Wolf.

With that said, we love steel cased ammo in our AR rifles. Reason number one being that it’s cheap and it flat out works well most of the time.

The faults of steel cased ammo are that it can expand inside your chamber causing a failure to eject. Another problem is that it gets your gun dirty as a pig in mud after you’re done shooting. Malfunctions are almost guaranteed to happen when shooting with steel case stuff but at the price you’re paying, it might be worth it to you to get over it and clear a few double feeds or stuck casings inside your rifle.

In fact, by the time you wear down your barrel and AR internal parts with steel ammo, you’d have saved enough money vs. buying brass to buy yourself a whole new gun anyways.

If you love going to the range and actually using your AR, go ahead and buy steel cased ammunition. That is unless you’ve got the money for brass.

AR-15 Cases – What to Buy

Here’s another topic that we wrote a comprehensive guide on. In fact, our guide to the best AR-15 case is over 2,000 words long and contains reviews of several soft and hard cases for AR-15 rifles.

In short, you should be looking for adequate padding, an easy to use latch system or zipper and plenty of magazine storage in your AR-15 case.

There You Have It

We hope that after reading this entire article on how to build an AR and learning about the different parts and such that you’ll come away as an educated consumer. We’ve helped many AR-15 newbies with their builds and fielded a whole ton of questions about the topic of building an AR.

At the end of the day, your budget and skill level will determine what you buy. The good news is that you have an incredible amount of options to build the AR rifle of your dreams.