My review of the Smith and Wesson Sport model AR-15 as a budget AR is one of this site’s most popular articles. A lot of people want to buy an AR style rifle while they still can. But for many, money is tight and they may not have the cash needed to buy a decent AR. So to these folks I say, “Then buy the parts you need over time, and build it yourself!”

Before you completely dismiss this idea because you believe it is too hard, too complicated, and you just don’t have the know-how, stop! Putting together an AR is really NOT that hard. You can do it in about 30 minutes or so. And you do not need a wide variety of tools. In many cases, you can purchase a completed upper and lower receiver, and simply connect them together yourself in mere minutes.

At the end of this article I have all sorts of links and resources available to help you buy the parts and build your own AR, including a video showing you step by step how to completely assemble an AR. So if you don’t need any further convincing, skip to the bottom of this article to get started! Be sure to check out part II of this series, Premium Builds!

Now if you still aren’t sure, let me give you some reasons why I think now is the time to get this project started!

Regardless of whether you build or buy an AR, if you want one I strongly encourage you to get one now! This site is not a political site, as I believe that being prepared transcends political parties. But the “gun control” drum is being beaten loudly, and it would not surprise me to see some in our government try to strip away the 2nd amendment rights of its law abiding citizens.

These rifles have been banned before, and it can happen again. This despite the fact that a majority of Americans are opposed to banning these types of rifles. So if money is a concern but you want to own an AR rifle, then start buying the pieces now while you can!

For the purposes of this article, I will be talking about building an AR-15 that is calibrated to fire the 5.56/.223 round. You can build variants that shoot the 300 blackout round, the 6.8 mm round, or the .308 round. (AR-10) But these builds are generally more expensive than the standard AR platform. So I am just focusing on the 5.56 version. (Although there is no real difference in building them, just different part sizes.)

Keep in mind that there are rifles out there that are chambered in .223. These rifles CANNOT fire a 5.56 round. But a rifle chambered in 5.56 can also fire the .223 round. So I strongly urge you to buy a 5.56 caliber rifle or barrel.


Benefits of Building

To me, there are some big advantages to building your own AR as opposed to buying a completed one. The first advantage is that you do not have to drop all your money on it at once. When building an AR, you can buy the parts over time, as funds become available. And if money is a concern, you can save a considerable amount by building your AR yourself. In some cases, you can save 20% or even 30% of the cost of buying a completed one!

Second, when you build your rifle, you are able to customize it and build it the way you want! This isn’t to say that you cannot accessorize a store bought AR. But it is easier to do when building your own!

Third, I believe you gain a better understanding of your rifle and how it functions when you build it yourself. I have built three ARs, and my knowledge on this type of rifle significantly increased when I put them together myself.

Sure, I had field stripped an AR before to clean it. But now I had a better understanding of what the pins, springs, and detents did, and how they worked. I had a better understanding of how the trigger group worked. I learned so much more by building my own AR!

Before we go any further, I do have to say that you need to check your local/state laws and ordinances to ensure you can legally own and possess these rifles. Unfortunately, these rifles are banned in a few states, and are heavily restricted in others. So make sure you can legally own one and if there are any restrictions in your area before going any further.

Parts of AR

If building your AR is the route you want to take but are completely new to ARs, let me fill you in on some of the nomenclature of the AR. This will make it easier when you go to buy parts.


It looks daunting, but do not feel overwhelmed. It’s easier to assemble than you think!

AR Lower in mid build

The only part that is serialized on an AR is the lower receiver. So in order to purchase this part, you must fill out a ATF 4473 form and complete the back ground process. If you order the lower receiver through the mail, it will be shipped to a FFL dealer, who can do the transfer for you. (For a small fee usually.)  So find a local firearms dealer you trust! All other parts can be sent directly to you.

As for the upper (or barrel), the National Firearms Act (NFA) states that any AR barrel under 16″ in length (or the overall length of the rifle is under 26″ and has a collapsible stock) is considered a “short barrel” rifle (SBR). SBRs fall under the rules set by the NFA.

Note: in addition, you can have a barrel that is 14.5″ in length IF it also has a permanently attached flash hider and/or compensator that brings the length out to 16″. 

SBRs are legal in many states, thought there are some guidelines you need to follow. I won’t be going through all that here, as those rules and guidelines could take up their own article. Suffice to say that the links and resources I’m listing here are for rifles barrels that are at least 16″ in length so that you do not have to worry about violating the NFA with a short barrel rifle.

I would also recommend an AR wrench to help tighten the “castle nut”and a bench with a vise. But you don’t have to have them.

Having a AR block which you can set you AR on is pretty handy as well. And none of these tools are terribly expensive. Yet each will help you every time you need t0 work on your AR. So having them available even if you buy a completed AR is not a bad idea.

Lower Receiver

There are four  types of lower receivers. You can purchase a lower receiver that is cast aluminum, billet aluminum, forged aluminum, or one that is polymer.

I will be upfront and tell you that I have never owned nor shot an AR with a polymer lower. (Glock pistol frames are polymer.) So I do not feel qualified to give an experienced opinion on these. Polymer lowers are typically lighter than their aluminum counterparts. But there were initial concerns with polymer lowers breaking at the buffer tube threading. There was also some concern about polymer receivers being weak at the front hinge pin. But again, I have never owned nor used one.

Completed lower receiver with buffer tube spring and stock

If you decide that you want to go with a polymer lower receiver, do your home work on it! I’m not saying polymer lowers are bad. Some of the arguments against them are similar to the arguments against Glock pistols back in the 80s. And look how that turned out.

But I’m not saying they are good either. There simply isn’t enough long term data out there on them. So know the risks before you purchase one.

Cast aluminum receivers are made when molten aluminum is poured into a mold. These are typically cheaper to make and buy. If purchased from a reputable manufacturer, these receivers will work just fine.


Billet aluminum receivers are formed from a solid piece of aluminum. It is “cut” into the shape of the receiver. A forged aluminum receiver is also formed from a piece of aluminum, but it is “hammered” into shape.

Forged receivers are considered the strongest of the receivers, though many people like billet receivers because they are much easier to personalize and more aesthetically pleasing.

When you purchase a striped lower, you will have to add the parts kit yourself. The parts kit typically includes things such as the trigger group, pins and detents, etc. You will also have to add the buffer tube, spring, stock, etc.

You can also purchase a completed lower which already has these items installed.

Many times I see various companies sell “blemished lowers”. These lowers are perfectly fine. They simply have scratches and scuff marks on the outside finish. You can get some REALLY good deals on these if you shop around.

There are all sorts of things you can do to customize your AR lower. From adding in a high end trigger group, to tungsten heavy buffers, etc, you can certainly spend a great deal of money here. But when trying to stay on a strict budget, I’d skip these pricey upgrades for now.

As I said, the lower receiver is the part of the rifle that requires a background check. If ARs are banned, this will be the part that can no longer be sold legally. I have seen striped lowers for as cheap as $30. So this is the part I recommend getting first.

Upper Receiver

There are some things you need to know about AR uppers. For starters, there is a lot more complexity with the uppers than with the lowers. I’m going to give you just an brief run down of the AR upper systems, barrel types, and other terms and differences you might encounter while shopping for parts.

Direct Impingment vs Piston

There are two types of systems in an AR. The first is a “direct impingement” system.  Wikipedia defines that system as:

Gas-operation is a system of operation used to provide energy to operate autoloading firearms. In gas-operation, a portion of high pressure gasfrom the cartridge being fired is used to power a mechanism to extract the spent case and chamber a new cartridge. See pic below….


With a long-stroke system, the piston is mechanically fixed to the bolt group and moves through the entire operating cycle.


Both systems have their pros and cons. Gas systems are usually lighter weight, more accurate, and the parts are MUCH easier to interchange. Piston systems are cleaner, cooler, and are not as finicky about ammo.

There is so much more we could cover on these two systems. But the purpose of this article is to help you build an AR on a budget. And gas systems are generally MUCH cheaper than piston systems. So with that, we will stick with a gas system.

Gas System Length

When it comes to gas systems, there is a small gas port in the barrel that vents gas with every round. This gas travels through the gas block and gas tube into the receiver, where it powers the bolt carrier group and cycles the next round. (See above pic.)

As the length of the barrel increases, so too will the length of the gas system, ie the length from the receiver to the gas port. For a rifle with a barrel of at least 20″, the distance from the receiver to the gas port is 12 inches.

For the M4 carbines with a barrel of 14 inches, the carbine gas system length is 7″.

With the introduction of civilian ARs with a 16 inch barrel, the mid-length system (9″) was brought in. So when you see a carbine system vs a mid-length riflesystem, you will now know what they mean.

I prefer the mid-length gas system over a carbine system for my 16 inch barrels. Why? Because there is less recoil and the cycling is smoother. But there is nothing wrong with having a carbine system with your 16″ AR. (Especially if you use a heavy buffer.)  Some folks believe that the carbine system is more reliable. It really comes down to personal preference, and I have not noticed a huge price difference between the two.


Most barrels you look at will be chrome lined, though there are stainless steel barrels as well. Chrome lined barrels are more durable and easier to clean, while stainless steel barrels are more accurate. I have owned a stainless steel barrel AR, and I did find it to be more accurate.


I would usually recommend a chrome line barrel as they are more robust and will have a greater life span. If money is a huge issue, you could get the non-chrome lined barrel. Just be forewarned that the life span of the non chrome lined barrel won’t be as great.

Rifle barreling will typically be either in a 1:7 or a 1:9 twist. There are rifle barrels out there that come in a 1:8 twist. My stainless steel barrel was a 1:8 twist rate.

Wait…..what? What is twist rate you ask?Ok…to break it down in layman’s terms, the bullet needs to spin in flight in order to maintain accuracy. The rifling in the barrel is what makes the bullet spin.  The tighter the twist, the more revolutions the

So a bullet in a barrel with a 1:7 twist will make one complete revolution every 7 inches. A twist rate of 1:8 is one revolution every 8 inches, and so on. The heavier/longer the bullet, the more spin it needs to stabilize. The more spin the bullet needs, the more revolutions it needs to make. So the lower the second number on the twist rate, the more revolutions your barrel will make on a bullet.

As you can see in the picture below, the better the twist rate, the larger the bullet you can accurately fire. A 1:9 twist barrel a usually a bit cheaper than 1:7 barrel, but I still prefer the 1:7 twist. It seems to handle the difference size rounds better.


If you are on a budget, I would probably suggest a barrel with a 1:9 twist to save a little money. 55 grain ammo is cheaper than the heavier grains, and a barrel with a 1:9 twist fires the 55 grain very well.

I mentioned earlier about various rifle barrel lengths. In addition to the 14.5″ and 16″ length, you can also get barrels that are 18″, 20″ and longer. But again, if you are on a budget and looking for a purely defensive AR, I would stick with the 16″ barrel. They are usually lighter, and easier to control in tight situations.

Barrel thickness might also come up. There are lightweight contours (pencil), standard M4 barrels, and heavy duty barrels. Obviously the pencil barrel will be lighter, while the heavy duty barrel will be more durable and have a longer life span. I would recommend the standard M4 as it offers the best of both worlds. But again, if money is an issue, the cheaper pencil barrel is not bad.

A word of advice here…the two areas on your AR where I would spend the most money possible to get the highest quality you can would be the barrel, and the bolt carrier group.

Bolt Carrier Group (BGC)

The BCG is the “heart” of your AR. Below is a video explaining exactly how the BCG works.

As I stated above, if you can spare the money, I would get a high quality BGC.


With any BCG, make sure that the gas keys are well staked with grade 8 fasteners. These are the two small hex bolts on the top of the BCG. This is important to prevent the hex bolts from backing out or coming loose due to the pressure of the gas. The bolts coming loose or out will cause a failure with the BCG.

I also want a BCG that has been magnetic partical inspected and high pressure tested. This means the BCG has been tested to ensure that there are no slight cracks or fractures in the metal.

Two of my ARs have a nickel boron BCGs. Nickel boron is a coating process that makes the BCG slicker and easier to clean. which make them much easier to clean. I also recently purchased a nickle Teflon BGC as well. More on that later. But again, this is a luxury you may not be able to afford. Just make sure the gas keys are staked properly and it has been properly inspected.


Most uppers that I see will already have handguards (or free floating tubes) in place. I really like the free floating tube as shown here on the rifle on the left. But I also have the Magpul MOE hand guard on my other AR, as shown on the right.

The standard handguard is the cheapest, though the rail guards and tubes are easier to accessorize.

Basically, it comes down to cost and personal preference. Both work well.

Other things to keep in mind

You will hear the term “Mil-spec” repeatedly when it comes to ARs. This is short for Military Specifications. For any item produced for the US military, it must meet certain standards before the US military will accept it…ie it must meet Military Specifications.

For example, Colt currently has a government contract for producing rifles for the US military. Their military rifles must be true “Mil-spec”. While Colts does sell ARs to the general public, they are close to mil-spec but not TRUE mil-spec. (The Colt 6920 is the closest a civilian can get to owning a TRUE mil-spec rifle.) Colt obviously has to make subtle differences to the civilian ARs so that they can legally sell them.

For civilians, the term “Mil-spec” is more of  an industry standard dealing with dimensions and tolerances. Companies that manufacturer ARs and AR parts try to get as close to the military standard without actually having the military inspection process. This ensures that the different parts will fit together correctly.

So regardless of your AR budget, don’t get too caught up in this terminology. For example, billet lower receivers are not considered “mil-spec” because the US military does not use billeted receivers. They use forged lower receivers. That does not mean billet is no good. In fact, billet receivers are typically well made.

rifles3So do not worry too much about this or that being mil-spec. You can still have a decent AR rifle even if it is not “mil-spec”!

However, keep in mind that there are two “sizes” when it comes to AR-15s buffer tubes; mil-spec and commercial. These sizes are not interchangeable with each other. So be sure that all the “buffer” parts you buy are either Mil-spec or commercial. Commercial tubes are usually cheaper, while mil-spec tubes are stronger, especially in the threading.

It is also important to note that many companies that sell rifles and parts buy those parts from the same manufacturers. For example, CMT produces parts for companies like Colt and Smith & Wesson. LAR produces parts for companies like Bushmaster, Spike’s Tactical, and Noveske. So keep in mind that many times the actual brand of the parts you buy do not mean much. It’s the manufacturer who matters.


Links and Resources

Ok…I hope you don’t feel inundated with all this information. I know that was a lot to take in. But trust me, there was A LOT I left out. Trigger groups, optics, sling mounts, etc. Those items can be added/upgraded later, when funds become available.

Anyway, I wanted to list some excellent resources where you can buy quality parts, tools, etc. On some of these sites you can find great deals and really save some money.

I do not have any sort of monetary arrangement with any of the websites listed below. I have these sites listed because I believe in them and have used them, and NOT for any sort of compensation purposes or personal gain. (ie I’m not getting paid to list them. I’m listing them because I personally believe in them!) – an absolute treasure trove of information about AR15s.

Palmetto State Armory (lowers) – They have some really good deals. I check here often

Palmetto State Armory (uppers/kits) – Some really solid parts. PSA makes quality parts

Kentucky Gun Company – They have some good deals from time to time

Cheaper Than Dirt – I don’t use this site as much now as I used to. But you can still sometimes find some nice deals – Great resource site for finding great deals on firearms, ammo, and accessories

Full30 – Website with videos dedicated to firearms and the 2nd amendment. Think of it as Youtube for guns!

Building your own AR revisited – Premium Build – If you have more $$ to spend and want a high quality AR, click this link to learn more.

Did I miss some sites? Let me know by messaging me here. I’m always on the look out for more great firearms websites and vendors!

Using the above websites, here is an AR 15 (parts) I could purchase and assemble for around $468 not counting shipping costs or the tools needed. And this is me just spending 20 minutes or so online. If you shop around, and take your time and wait for good deals, you could get it even cheaper!


Once you have all your parts, below is an excellent video that takes you step by step through the AR15 construction process.





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