The Ultimate Guide to Buying Your First AR-15

Although many of you are already well-versed with the AR-15, there are many new firearm enthusiasts that are entering the market every day.

Because of the popularity of the AR, almost everybody wants to get at least one. When deciding on your first AR-15, there are a couple of key things you will want to consider before making your purchase.

Let’s take a look at what you want to look for when buying your first AR-15.

Build Type: Fully Assembled, Partially Assembled or From Scratch

There are three main AR-15 build styles:

  • You can buy a complete rifle.
  • You can piece together completed upper and lower receivers.
  • You can do a complete build from scratch.

For your first AR, I would suggest selecting a good-quality complete rifle from a reputable manufacturer. This tends to lead to a more reliable firearm, especially if you don’t have experience building an AR-15.

If you don’t find a complete rifle that you like, then you may want to consider purchasing a complete upper and lower receiver assembly. That is much easier to piece together—just two pins—and can still lead to a reliable rifle.

This allows you to make sure your complete firearm has all the features you want if you cannot find them on a factory-built rifle.

(Learn more about AR-15 builds here and here.)


Classification: Commercial or Mil-Spec

Commercial or Mil-Spec? This will determine the buffer tubes and stocks you are able to use. The two need to match—Mil-Spec with Mil-Spec and commercial with commercial.

With modern-day components, there is not really much of a difference in quality and availability, but most shooters tend to prefer Mil-Spec.

Mil-Spec was the original, but companies realized they could produce the tubes cheaper by making the tube slightly larger in diameter (0.02-inch) and cut the threads in, as opposed to Mil-Spec where threads are rolled in.

There is no evidence to suggest that either option is stronger or more durable.

AR Receivers and Buffer Tubes
Credit: @BDavidson78681 (Twitter)

Operation: Direct Impingement or Gas Piston

Piston is more expensive, but it is thought to be a lot cleaner on internal parts, though I have had no problem with my direct-impingement firearms.

Direct impingement is a simpler mechanism with less to go wrong. In a direct-impingement firearm, the gas is directed up into the gas tube and forced back into the gas key.

This force pushes the bolt carrier group back and operates the semi-automatic action. In a gas piston firearm, when gas forces reach the gas block, they stop and hit a solid piston.

The piston then cycles back and forces the bolt carrier group back and operates the semi-automatic action.

The piston traps most of the carbon build-up and keeps the rest of the rifle cleaner, making it easier to clean and theoretically able to run longer between cleanings.

Rifles on Table
Credit: @hisbabe12082017  (Instagram)

Receivers: Forged, Billet or Cast

Most AR receivers are made out of heat-treated aluminum and are either forged or billet. Cast receivers exist, but they are scarce and not typically great. Receivers are either constructed of 6061 or 7075 aluminum.

  • 6061 tends to be less expensive and durable, but is also more corrosion resistant.
  • 7075 is a stronger material and more costly, but tends to stand up to abuse a little bit better.

Forged receivers are made by hammering two roughly shaped halves together, then cleaning them up later with machines. This method is quicker and cheaper to produce and still leads to a quality rifle.

Billet receivers are made by taking a single block of aluminum and a CNC machine milling out the lower. This method takes longer and is more expensive but allows for more unique designs and patterns.

Hammer-hardened forging tend to make the lower more durable and they are lighter weight because of less excess material, but with modern materials, a good 7075 billet lower is basically just as strong.

There are also polymer receivers, which have come a long way in past years. However, my suggestion would be to stay away from polymer lowers because they tend to have issues.

Unless you’re going for an extremely light-weight build, they are not the best choice, especially for your first AR-15.

AR-15 Receivers
Credit @trevor_hirby (Instagram)

Parts and Accessories

Gas Block

You will also want to take a look at the style of gas block used in the rifle. Many starter AR-15s are equipped with a standard A2 front sight post and gas block.

This is a solid starter option, especially if you only intend to use iron sights. If you want to install a free-float handguard, you will need to have a low-profile gas block.

This is easy enough to install later on if you choose. If the rifle or upper receiver you are looking at already has a free-float handguard, it will already have the low-profile gas block installed.

One final consideration to make would be an adjustable gas block. These are typically not recommended for defensive use because they can sometimes affect reliability, but they are great for competition.

Adjustable gas blocks allow the user to regulate the amount of gas pressure sent back to the bolt for different ammunition loadings.

They are also great for suppressor use because you can adjust the gas pressure to make sure your rifle functions properly.


Many budget rifles do not come with iron sights. This is a cost-saving measure on the part of the company, as they assume most users will want to install their preferred sights or optics anyway.

If they are not included, however, you will want to factor this into the overall cost, as your AR-15 will be virtually useless at any range without a sighting system.

If you are looking for basic sights for your first AR, Magpul makes a quality set of both polymer and metal flip-up sights that can be had at an affordable price.


Most ARs will come with at least one magazine, though I have seen some that don’t.

Make sure to check on this when you do decide to purchase, and you may want to consider grabbing some additional mags for an easier time at the range.

Magpul P-Mags have basically become the industry standard, and have even made their way into military service. They are incredibly affordable and reliable.

P-Mags can be found for incredibly low prices, usually between $12-20 a piece, depending on the generation and whether you would like clear window cutouts to quickly view your remaining ammunition capacity.

How many magazines do you need? This is entirely personal preference and dependant on what you purchased your AR-15 for. However, I personally like to keep around 10 magazines per rifle.

You do not need to gather theses all at once, you can add to your collection as your budget allows, spending another $15 here and there. (Read a review of the above UTG AR-15 mag here.)


There are tons of options for handguards for the AR-15. Most budget rifles will include a standard GI style, plastic two-piece system.

This is an OK start, especially if you don’t plan on firing the rifle much, but it certainly is not the best option. These typically don’t contain a heat shield and can easily crack if dropped.

You can easily replace these with two-piece handguards from Magpul that are a bit more robust and include a steel insert heat shield that aids in heat dissipation.

They also allow for the attachment of rail sections so you can mount forward grips, lights and lasers.

If, however, you want the full tactical look, you may want to consider finding an AR with a free-float rail (either KeyMod or M-LOK). This can be added on later as well, but it is more difficult.

This can not only aid in improving accuracy in the hands of experienced marksman but allows for a multitude of attachment points for your various gadgets.

Deciding between M-LOK and KeyMod is mostly up to user preference. Both allow for more space on the rifle to place your hand and attach accessories, the difference is only in the method of attachment.

Most people turn to M-LOK because it is more secure.

But KeyMod will most likely serve you just fine and these handguards are often discounted, though only time will tell whether parts availability with KeyMod will begin to die down.

One final consideration is the quad rail handguard.

The modern tactical community typically considers these outdated because they add unnecessary weight, but they are perfectly functional and offer quite a lot of attachment space.

These can be found in either two-piece systems as well as free-float versions.


Choosing a stock is largely dependent on personal preference. Most are collapsible, six-position variants (if that is legal in your state).

However, you can also find fixed stocks and attachments to make folding stocks.

One important thing to remember is that you must have, at minimum, a 16-inch barrel to attach a stock without filling out required ATF paperwork to file for a short-barreled rifle.

We’ll touch more on this later, but for now, just keep that in mind. Most stocks will feel very similar when pressed up against your shoulder and will perform the same basic function.

If you are not satisfied with a standard M4 stock, just select a one from a reputable manufacturer such as Magpul, BCM or FAB Defense.


Most entry-level AR-15s will come with a standard single-stage trigger. A single-stage trigger has very little, if any, take-up and has a nice, crisp break right as you pull.

This is a good starting point for most users and is great for quick follow-up shots, but tends to not be as conducive for accuracy at long ranges as a two-stage trigger.

A two-stage trigger has some travel before the break, referred to as “slack” and then reaches the crisp break.

This allows you to stage the trigger until the breaking point, and can then complete the travel when you find your perfect shot.

Depending on what you want to use your AR for, finding a rifle with a reputable two-stage trigger may be preferable. Deciding on a single-stage or two-stage trigger is personal preference.

Some like the security of having some slack in the trigger before the break—whether that be for accuracy purposes or a sort of safety in a defensive scenario—and therefore lean towards two-stage triggers.

Others prefer the quick, crisp break of a single-stage trigger. My suggestion is to try out each at your local range or gun store and decide for yourself.

(Learn more about AR-15 triggers here.)


Staking the gas key keeps it properly attached to the bolt carrier through the extreme force the gas exhibits on the unit. The point of staking the gas key is to keep the screws from working loose.

This is due to the frequent back and forth movement by adding extra friction, while still allowing the removal, if necessary for maintenance or replacement, through extreme force.

If the gas key comes loose, it can cause malfunctions and your AR-15 to not operate correctly.

There’s a lot of debate about this one, but you may want to consider finding a rifle with a staked castle nut or staking it yourself. The reason for this is that staking makes sure your castle nut doesn’t come loose.

The castle nut holds your buffer tube assembly to the AR-15 lower receiver, if this works itself loose it can cause issues in reliability and durability of the firearm.

Most castle nuts will have a notch included where you will be able to stake them down. This action is typically considered permanent, but you can remove it if you need to with an armorer’s wrench.

Other options include applying a small amount of Loctite on the threads or simply to torque down the castle nut and hope for the best.

Size/Barrel Length: AR Pistol or Rifle/Carbine

Finally, you will want to decide on the size and barrel length of your AR-15. Most first-time buyers select a 16″ “carbine-length” platform, but that is not to say that it is for everyone.

The emerging trend is to get short-barreled ARs, which are classified as pistols until you decide on filling out the proper ATF paperwork, attaching a true stock and making it a short-barreled rifle.

It is important to remember that you can go from a registered pistol to rifle, but not vice-versa. A 16″ barrel is as low as you can go with a firearm that is legally defined as a rifle; anything shorter will be considered a pistol.

An 18″ barrel is considered “mid-length” and anything above is called “rifle-length.”

All lengths have their benefits. The shorter you go, the more maneuverable and lightweight the firearm is, while longer barrels have higher ballistic performance and longer range capabilities.

Decide on what you want to use your AR-15 for and then select the barrel length that best fits your application.

AR-15 Pistol
Credit: @hilltoptactical (Instagram)


Whatever AR-15 you decide on, make sure you are happy with it. Don’t go out of your way to buy the firearm other people think you need.

You do not need to spend thousands of dollars on a Gucci AR. For example, many shooters are completely satisfied with a standard Ruger AR-556 or Smith & Wesson M&P Sport II.

ARs are like the LEGOs of the firearms world. If you want to add or change features later, you can always do so on your own time.

Just make sure you take the time to know what you are looking at before you buy so you don’t regret your decision later.

Buying First AR-15
Credit: @bjiep11 (Instagram)

What was your first AR-15? Which style did you choose? Let us know in the comments below!

About the Author:

Alex Cole

Alex is a younger firearms enthusiast who’s been shooting since he was a kid. He loves consuming all information related to guns and is constantly trying to enhance his knowledge, understanding, and use of firearms. Not a day goes by where he doesn’t do something firearms-related and he tries to visit the range at least a couple of times a month to maintain and improve his shooting skills.

His primary focus is on handguns, but he loves all types of firearms. He enjoys disassembling and reassembling firearms to see how they work and installs most of the upgrades to his firearms himself, taking it as a chance to learn. He’s not only interested in modern handguns and rifles, he appreciates the classics for both historical value and real-world use.
The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (20)

  1. I’d argue that Keymod is already going the way of the Dodo. Otherwise, spot on and a great article for people looking for their first AR.

  2. @ALEN — So you are the Jump Master responsible for all the broken ankles during the night jump? — Just kidding … I went through basic back in ’87 — with a large group of airborn-chairborn (clerks destined for the 82nd) — a bunch of them washed out during jump school, apparently on the night jump — we did not see them again during AIT. I do not jump out of perfectly good airplanes, especially at night 🙂

    So to answer your question: The gas key is the block (held in place by two hex bolts) with small tube sticking out above the bolt carrier assembly (it fits into the end of the gas line on the direct impingement AR’s (piston ones do not have it — that’s how you tell the difference at a glance as to what kind of bolt carrier group it is). You “stake” those bolts down — that’s the 2 notches on the left and right of the hex bolts that will prevent them walking out because of the vibration. (see the pic right after the stakes label). You also “stake” the castle nut. it is the nut that holds your buffer tube assembly to your “lower”. It looks like the top of the medieval turret (with crenelations) hence the name. This is the other part that’s always impacted when you are firing — the gas pushes the bolt carrier group back into the spring that will compress and then force it forward again. The reasons for “staking”: The force of the gas shocking the bolt and the castle nut during firing may loosen (the bolts and/or the castle nut) through vibration. See the benefits of drinking with armorers …

    I’m a NOOB myself — I’m just planning my first AR build. I started with a basic S&W MP-15 (butchered to comply with idiotic NJ laws). I’ve already tweaked it a little — I added the HIPERFIRE Enhanced Duty Trigger Sharp Shooter (EDTSS). It completely transformed the feel of the weapon (. Like the article said — AR is an infinitely modifiable platform. With very few tools and after watching excellent video on YouTube — the most difficult part of the job was getting the damn trigger out of it’s packaging. Zero skills required. This is what started me going down this AR modding road, also it combines my two favorite pastimes shooting and making things …

    It’s not at all like an AK build — you’ll need a 12 ton press for that one …

  3. I purchased my first AR-15 just before the ban went into effect. It was a Bushmaster Patrolman carbine, made by the original company when it was still a separate entity located in Maine, with a M16A2 style heavy barrel, a removable M16A2 styled removable handle that converted it into a M16A4 flat top, and everything else Mil-Spec. I put a Bushnel Holosight, really an EOTech 512, on it. I had a great time with it until the firing pin retaining pin broke and probably gouged up the upper receiver. I still have it in mid extraction when the pin broke. One day I’ll slowly take off the extension tube to release the pressure on bolt carrier group and extract the brass from the extractor. Hopefully, the upper receiver isn’t gouged up. Been too busy making AR’s to get around to it.

  4. My first and only AR is a Sig Sauer M400 with a fixed front sight and Magpul furniture. It shoots great with open sights at 300 yards or less. I was a Kalashnikov hardliner, but the comparative accuracy of this rifle has changed my outlook. I have had a few failures to load with ProMag magazines. It has otherwise been reliable with PMC, Winchester, Federal and Wolf steel case 5.56 and .223 – both 55 gr and 62gr when using Magpul Pmag magazines.

  5. Build your own. There are a lot of tutorials -check on YouTube. Pick up a nice lower priced lower like Anderson, then check out a place like Outdoorsportsusa that carries kits that have everything you need for your build. You’ll learn a lot and It’ll mean more to know you made it yourself.

  6. My first AR was purchased in 1991. It is a Colt with a 20″ barrel. I now own a few from a 10.5″ barrel pistol I built the lower for to off the shelf in 16″ carbine configuration. I am planning another build in the future to be a highly customized 18″ barrel rifle. The AR is truly America’s rifle.

  7. As a relatively newcomer to the AR platform I have learnt a lot and against other “well qualified” experts I clean my BCG after each session.

    SOOOO what are the gas keys and where do I find info on them, the Ruger manual makes no mention. This is what confuses us newbies, “experts” trying to explain when basics are overlooked makes the industry look sallow.

    If I trained my first jump students in this manner there would be a few causalities. Same thing in the gun industry..

    Please educate me on where and what the “gas keys” are located and their appearance.

    Thank you

    Wilson Combat AR-15 Bolt Carrier Group
    Staking the gas key keeps it properly attached to the bolt carrier through the extreme force the gas exhibits on the unit. The point of staking the gas key is to keep the screws from working loose.

    This is due to the frequent back and forth movement by adding extra friction, while still allowing the removal, if necessary for maintenance or replacement, through extreme force.

    If the gas key comes loose, it can cause malfunctions and your AR-15 to not operate correctly.

  8. Hi…I started out with a typical Bushmaster AR-15 in the A-2 configuration. But I didn’t like the set-up for 3-gun matches, so I traded it out to put a flat top upper on it. I played around with that for several years, and actually put together a couple of guns from Palmetto, switching out uppers and lowers to see what I liked. Actually..I liked most of them!! Then I finally put out for a REAL competition gun – the BAMF from Cobalt Kinetics. This is a great piece, and really built for 3-gun in 223 Wilde. This is really a good idea for a first AR – get the 223 Wilde barrel, then you don’t worry about shooting 5.56 OR 223 – just shoot anything! Now I went the SBR route, so I can shoot that in PCC matches using the 9mm barrel. This is fun, because you can change out barrels and shoot a variety of calibers on the same platform. Anyway…good article. Need to pass to some of my friends.

  9. My daughter and grandson are both left-handed and also left dominant eyed, so I assembled an AR using a Stag Arms left-handed upper (blem) , an Anderson lower set up all ambi controls. I also added a CMMG LH .22 LR conversion kit. I’m right-right so test firing was interesting with the lefty ejection port in front of my face. cases exited at 90 degrees. Functioned well with both .223 and .22 lr ! Magpul furniture, Keymod forend and 3-9 optic.Nice AR for my Lefties, Good Poppy and grandson project.

  10. I bought the Springfield Saint Victor for my first AR. It’s a very nice, way shooting rifle. At around $850, it included two mags and a nice soft sided case. My buddy bought something a couple hundred dollars cheaper. One mag, no case and you feel every shot. His has the plastic hand guard and it isn’t freefloating. Everything else is basic as well. As the article says, take your time and do your research. And if needed, take the time to save the money so you can get what you want first. You can upgrade later, but to me that’s a waste of time and money.

  11. I shoot a Delton Sport and love it, It serves my purpose. The only changes I have made is to ad a MFT buttstock; a Magpul MOE pistol grip & trigger guard; a short Magpul rail to the factory handguard to mount a light; a magpul flip-up polymer back-up sight & a Walther red dot. The carbine is light, accurate & fast to get on target. It is my plinker, home defense rifle & occasional hog-hunting partner. Everything I need without spending a fortune. She has seen 1000 rounds with no failures of any kind.

  12. Great article! Well written, even handed review. Best advice in the article: try it for yourself and see what you like (ie shoot best, most comfortable) instead of chasing the latest trend. The Freedom to buy, chose, discard, try again, mix and match is only one of the attributes that makes this such a great platform.

  13. Ruger AR556. Only change I made was a flip up front sight, a red dot, and a light. Like Ruger products, they last, and have NEVER given me trouble.

  14. About a year and a half ago, I was at the Navy Seal Museum in Florida where i registered to win an AR15. I bought 1 ticket not expecting to win. A few weeks later I got a phone call from the museum stating that I had won the AR15 and it would be shipped to our nearest gun dealer for pickup. It’s made by Blackhawk and completely customized with scope. At 50 yards, I can group them less than 2″. the manufacturer sent me a list of all the components of the gun. I am very impressed with this customized gun, caliphered at 5.56. It’s not every day that you buy 1 ticket and win. I am extremely happy.

  15. My first AR is a Windham Weaponry MPC. I liked the fact that it has a carry handle. And, I got really good deal on it. The only modification I have made was to replace the trigger with an ALG Defense Advanced Combat Trigger. It was totally unnecessary since the factory trigger was really nice. But, it’s so much fun to modify these.

  16. My first AR was a Stag Arms model 2L. I am right-handed, but left-eye dominant. It’s okay with pistols to shoot right-handed, but from an early age I shot rifles and shotguns left handed. Stag Arms is only one of two manufacturers making left-handed AR’s.

Your email address will not be published. Required fields are marked *

Your discussions, feedback and comments are welcome here as long as they are relevant and insightful. Please be respectful of others. We reserve the right to edit as appropriate, delete profane, harassing, abusive and spam comments or posts, and block repeat offenders. All comments are held for moderation and will appear after approval.