Everything You Need To Know About AR-15s [ULTIMATE RESOURCE]

Everything You Need To Know About AR-15s [ULTIMATE RESOURCE]

Posted by STNGR USA on Nov 17th 2022

Everything You Need To Know About AR-15s [ULTIMATE RESOURCE]

Everything you need to know, all in one place.

This resource is excellent for both beginners and seasoned shooters alike.

The STNGR AR-15 technical team will regularly update this resource to give you the most current information about the AR-15 platform.

Last updated: November 17, 2022


AR-15s 101: The Fundamentals

The AR-15s 101 Fundamentals Series gives you everything you need to know about the AR-15 platform.

You can choose to watch a video or read the info with additional images and graphics (or do both!).

This series is updated regularly with new topics. If you ever have any questions, please get in touch with STNGR's AR-15 technical team :) We're happy to chat any time!


#1: Intro to the AR-15 Platform

  • History of the AR-15
  • Intro to the two main parts of the AR-15: the upper and the lower

#2: Intro to the AR-15 Barrel

  • What an AR-15 barrel is
  • How barrel length impacts shooting accuracy
  • Discussion of twist rate (or rifling) and the effect it has on accuracy
  • Muzzle devices

#3: Intro to the AR-15 Upper Receiver

  • What the upper receiver is and the components of the upper receiver:
    • Bolt carrier group
    • Gas block and gas tube
    • Charging handle
    • Forward Assist
    • Ejection Port

#4: Intro to the AR-15 Lower Receiver

  • What the lower receiver is and the components of the lower receiver:
    • Trigger group
    • Buttstock
    • Buffer Tube
    • The grip

#5: Intro to AR-15 Ammo and Magazines

  • What is ammunition (also known as bullet cartridge) 
  • Full Metal Jacket (FMJ) vs Hollow Point (HP) bullets
  • 3 Most Common Rounds: 6.5 mm Grendel, .300 AAC Blackout, 5.56 NATO / .223 Remington.
  • What are AR-15 magazines

#6: Why does your AR-15 need a handguard?

  • Quick history and origin of the AR-15 handguard
  • How the original handguard was designed
  • 2 main purposes of the handguard
  • Why your AR-15 needs a handguard
  • Other functions of the handguard

#7: Free Float vs Drop-In Handguards

  • What a free float handguard is
  • What a drop-in handguard is
  • Pros and Cons of each handguard type
  • Which one is best for different shooters
  • What to do if you don't like your current handguard and want to swap it out

#8: M-Lok vs Picatinny vs Keymod

  • Discussion of the 3 main handguard mounting systems:
    • M-Lok
    • Keymod
    • Picatinny
  • Pros & Cons of each mounting system
  • Comparisons of all 3 mounting systems
  • Top picks for different functions

#9: Building vs Buying an AR-15

  • Pros & Cons of:
    • Building an AR-15
    • Buying an AR-15
    • Customizing an AR-15
  • How to determine which option is best for you

#10: Choosing an Optic For Your AR-15: Red Dot Sight vs Scope

  • Intro to and Pros & Cons of:
    • Red Dot Sight
    • Magnified Scope
  • How to choose the one that best suits your needs

#11: The Red Dot Sight for the AR-15

  • Intro to the red dot sight (RDS)
  • How it works
  • The different types of red dot sights
  • The mounts it uses
  • Advantages of the RDS & why you'd consider using it over a traditional iron sight

#12: The Low Power Variable Optic (LPVO) for the AR-15

  • Intro to the low power variable optic (LPVO)
  • How it works
  • Pros and cons of the LPVO
  • When to use a LPVO

#13: The 5 Best and 5 Weirdest Accessories

  • Top 5 picks for the best, most functional accessories for the AR-15 handguard
  • What we think are the 5 weirdest AR-15 accessories

#14: Single Point vs Two Point AR Slings

  • What are single point and two point slings
  • Where they attach on your firearm
  • Pros and cons of each
  • When is best to use single point vs two point slings
  • How to choose the one that best suits your shooting needs

#15: AR Pistol vs Short Barreled Rifle (SBR)

  • What is an AR Pistol
  • What is an SBR
  • Similarities and differences of AR pistols and SBRs
  • How to know if an SBR or an AR pistol is right for you

#16: The AR-10 vs AR-15 Platform

  • Intro to the AR-10 and AR-15 Platforms
  • The rounds that each one shoots
  • Situations where AR-10s are best vs when AR-15s are best
  • Discussion of whether you can interchange parts between platorms
  • How to know which platorm is best for your needs

#17: Should You Build Your Upper or Get a Complete Upper?

  • What you need (components, tools, skill) to build an AR-15 Upper
  • What's needed if you choose a complete upper
  • Pros and cons of a complete upper vs building an upper
  • How to decide which one is best for you

#18: Forward Grips vs Handstops

  • What is a forward grip? And what's a handstop?
  • Pros and cons of grips vs handstops
    • Weight
    • Control
    • Heat Management
    • Legality
  • How to choose the one that's right for your needs

#19: Rifle vs Mid-Length vs Carbine Gas Systems

  • Overview of the rifle, mid-length, and carbine gas systems
  • How the rifle, carbine, and mid-length gas systems are different
  • Recommendations for gas system lengths

#20: AR-15 Cleaning and Maintenance

  • Why regular AR-15 maintenance is important
  • How often you should clean your rifle
  • The right tools for the job
  • How to clean & maintain your rifle

#21: Matching Ammunition to Barrel Twist Rate

  • Overview of AR-15 rifling and twist rate
  • Which twist rate you should go with when choosing a barrel or upper receiver
  • Discussion of common twist rates and what they're used for

The Top Asked AR-15 Questions - Answered

All of your most pressing questions about AR15s, answered. The AR15 technical team here at STNGR will updating this list reguarly with new questions & answers.

If you have a question that isn't answered here, shoot us a message with your question and we'll add it to this list 👍


AR-15 Ammo/Bullets

Q: What kind of bullets does an AR 15 hold?

A: The kind of bullets an AR15 was originally chambered in was .223 Remington. Very similar to this is the 5.56mm NATO cartridge: AR15s chambered in 5.56 can fire .223 Remington, but .223 chambers should not be used to shoot 5.56mm NATO.

Q: How many bullets does a standard AR 15 hold?

A: The number of bullets an AR15 holds depends on the magazine. Without a magazine an AR15 only holds one bullet. Originally issued with a 20 round detachable magazine, capacity now depends on local laws and purpose (target shooting or hunting or defense or security), the popular capacities are 5, 10, 15, 20, 30 or even 40 and 90rd drum magazines.

Q: What is the most common ammo for AR 15?

A: The most common ammo for an AR15 is .223 Remington or 5.56 NATO. While almost identical, the NATO round is a little longer and should only be fired in 5.56 chambers. The .223 can be fired in its own chamber or 5.56 NATO. Another chamber called .223 Wylde can take both as well as its own. The AR15 can take different upper receivers in other calibers as well.

Q: What is the best AR 15 ammunition?

A: For the “standard” caliber of 5.56mm NATO, the best AR15 ammunition is often considered to be Federal XM193 55gr FMJ for 1:9 twist barrels and Federal XM855 62gr for 1:8 twist barrels. Similar bullets are made by other manufacturers such as PMC and PRVI Partizan.

Q: How much does AR 15 ammunition cost?

A: AR15 ammunition costs vary because AR15 firearms come in multiple types of calibers. The most common is .223 Remington which currently (November 2022) can run around 30-40 cents per round if purchased in bulk cases of target ammo or from 50 cents or over a dollar a round for specialty bullets for hunting and defense.

AR-15 Calibers

Q: What is the best caliber AR 15 to buy?

A: The best caliber to buy for an AR15 depends on what you want to do with it. The most popular caliber is .223/5.56NATO so this provides the most in aftermarket and spare parts. .22LR is more economical for target shooting and other calibers are available for different applications and tastes.

Q: What is the strongest AR 15 caliber?

A: The strongest caliber for the AR15 depends, again, on purpose. For range and holding knocking power out to about 1,000 yards, the 6.5 Grendel is the strongest. For greater “knockdown” potential at ranges under 300 yards, the .458 SOCOM and .50 Beowulf have similar performances. While these specialty calibers offer specific advantages, the standard .223 Remington comes in a variety of bullet types to deliver higher performances also.

AR-15 General

Q: Is a background check required to buy an AR 15?

A: A background check to buy an AR15 depends on your state and who you are buying it from. Federally speaking, any firearm purchased from a licensed Federal Firearms License (FFL) holder MUST go through a background check. Some states, however, allow sales between two private individuals: check with your local law enforcement to be sure.

Q: Is there a waiting period to purchase an AR 15?

A: A waiting period to purchase an AR15 or any firearm is no longer required *federally* – some states or local jurisdictions may have their own laws: check with your local law enforcement to be sure.

Q: Is there a break in period for an AR 15?

A: An AR15 does not need a break in period, but some believe that the barrel needs to have 20-200 rounds through it before they start trusting its accuracy and fine tuning the optics.

Q: What makes an AR 15 different than other rifles?

A: What makes an AR15 different from any other rifle is its modularity. Despite uninformed opinions, there are other rifles as effective as the AR15, or capable of quickly firing more powerful cartridges. With the ability to swap out the upper receiver, however, the AR15 can serve multiple roles from long range to close tactical/security. This includes changing calibers as well.

Q: What's the difference between an AR 15 and a shotgun?

A: The difference between a shotgun and an AR15 is that the shotgun generally has a larger bore that is smooth and does not (though can) shoot solid shot. An AR15 has a rifled barrel and shoots one solid projectile at a time.

Q: How many different AR 15 rifles are there?

A: There are hundreds of different AR15 rifles to choose from: between the brands and styles, the AR15 is the most variable and versatile of firearms on the market: which is why it is so popular.

Q: How many manufacturers of AR 15 are there?

A: From 1964 to 1977 Colt held the only patent to manufacturer the AR15 rifle. In the 1990s and 2000s most other gun manufacturers began producing their own AR15 style rifle and many more companies are an AR15 only maker. Today there are hundreds of AR15 makers with prices from just over $400 to thousands per gun.

Q: Are AR 15 more dangerous than handguns?

A: An AR15 is no more or less dangerous than any other type of firearm. While most gun crimes in the US are committed with handguns, the AR15 gets “bad press” more because of politics than anything else.

Q: How much does an AR 15 rifle weigh?

A: An AR15 rifle’s weight will depend on how many accessories are put on to it. To start, a 16” barreled “carbine” with iron sights without magazine weighs around 6.5 lbs (3 kilograms). A loaded 30 round magazine will add about another lb or about half a kg. Longer, or shorter, barrels and accessories will adjust the weight accordingly.

Q: What to look for when buying first AR 15?

A: What to look for when buying your first AR15 depends entirely on what you mean to use it for. But the AR15 can be rebuilt to new purposes down the road. For example, a general purpose AR15 with a 16” barrel is a good starting point, but if target shooting is the intended purpose than a heavier or longer barrel makes more sense.

Q: What is the difference between a cheap and expensive AR 15?

A: The difference between a cheap and expensive AR15 is both subtle and vast. Think of the two receivers of the AR15 (lower and upper) as cases for all sorts of features that can be put in as upgrades or bought complete. Even the receivers have different grades from forged to billeted, but the primary parts that drive up the price are the barrel, bolt carrier group (BCG), furniture (including stock and handguard with different features), sights and trigger. Because these all can be added on to any AR15 receiver set, it is possible to start cheap and build an expensive rifle – you might come in a little higher than buying an expensive rifle right out, but you can do it at your own pace and make the rifle the way you want it.

Q: Is AK 47 or AR 15 more reliable?

A: An AR15 versus an AK47 in terms of reliability is a varied concept. Because an AR15 is built to tighter tolerances it is generally more accurate than a stock AK47. The AK47 is considered less prone to failure due to fouling or dirt getting into the action. Popularly, an AK can take more abuse without failing than an AR while an AR is more accurate.

Q: What fps does a AR 15 shoot?

A: The FPS (feet per second) an AR15 shoots a bullet depends on the length of the barrel and the bullet itself. Out of a 16” barrel the common load (5.56 or 2.23) is around 3200 feet per second.

AR-15 Barrels, Barrel Lengths

Q: What to look for when buying AR 15 barrel?

A: Besides length, the thing to look for when buying an AR15 barrel is the rifle twist. Expressed in ratios of 1:9 or 1:8 or 1:7. The most common target and general purpose round for 5.56/.223 is 55 grain. This weight and lighter is meant for use in 1:9 twists (rifling makes one revolution in 9 inches). Heavier bullets (80grains or higher) do better (are more accurate) out of 1:7 twist barrels. 1:8 barrels are essentially a middling option.

Q: What is the life of an AR 15 barrel?

A: An AR15 barrel’s life expectancy is contingent on care and abuse. A well cared for barrel can see 20,000 rounds or more before suffering any serious loss in accuracy. Abuse such as frequent rapid firing and infrequent cleaning can reduce this, however.

Q: How many rounds can you put through an AR 15 before it's too hot?

A: It’s not an issue of how many rounds you can put through an AR15 before it’s too hot but how quickly. Usually, the barrel will start to get hot to the touch after firing three rounds in rapid succession. Firing rapidly will affect long range accuracy first and shooting 10 or more rounds as fast as possible will make the barrel too hot to directly touch.

Q: How long does an AR 15 barrel have to be to be considered a rifle?

A: In order to be considered a rifle, an AR15 barrel must be 16". A shorter length barrel is permissible IF the muzzle device is PERMANENTLY affixed to the barrel and the combined length is over 16”, however state laws may have different rules.

Q: What's the longest barrel you can put on an AR 15?

A: There is no maximum length barrel for an AR15, or for rifles in general. For performance with a 5.56/.223 cartridge, anything over 20” is generally considered unnecessary, though up to 24” is available for specialty bullet loads.

Q: What is the shortest barrel you can legally have on an AR 15?

A: The shortest length barrel you can legally have on an AR15 carbine or rifle is 16”. You can have a shorter length barrel if the muzzle device is PERMANENTLY affixed to the barrel and the combined length is over 16”, however state laws may have different rules.

Q: How long does a AR 15 barrel have to be to be a pistol?

A: In order to be considered legal, an AR15 pistol barrel length must be less than 16”. This means if the barrel is under 16” it is considered a Short Barreled Rifle (SBR) UNLESS the lower receiver is registered as a pistol and there is no stock.

Q: Are AR 15 pistols worth it?

A: Only you can decide if an AR15 pistol is worth it. AR15 pistols leave more space for the addition of suppressors and are more manageable than 16” or more barrels. They are only marginally more concealable than a carbine or rifle (if at all). AR15 pistols are also universally considered fun. All that said, AR 15 pistols are worth it if they fit your specific needs. Head over to a range and try out an AR 15 pistol so you can determine if it's right for you.

Q: What is needed to build an AR 15 pistol?

A: What is needed to build an AR15 pistol is the same tools and parts to build an AR15 carbine or rifle. There are 2 important differences: 1) the lower receiver (the part that is registered) MUST be registered as a pistol when purchased. 2) a pistol may NOT have a rifle-like “stock”. Presently, a “brace” may be used instead. Consult local authorities to not run afoul of local/federal rules which may have changed after this posting.

AR-15 Magazines

Q: What kind of magazine does an AR 15 use?

A: The type of magazine an AR15 uses is a detachable box magazine. Capacities range from 3rds for hunting to 5, 10, 15, 20, 30 and higher.

Q: How long does it take to change an AR 15 magazine?

A: The time it takes to change an AR15 magazine varies depending on training and situation. A shooter familiar with their firearm can drop the empty magazine, retrieve and insert the fresh magazine and charge the first round into the chamber in less than 3 seconds.

Q: Is it OK to keep AR 15 magazines loaded?

A: It is ok to keep AR15 magazines loaded, however, many people like to swap out their loaded mags after a period of time 3-6 months for example and let the previously loaded magazines be unloaded thinking it preserves spring tension.

Q: How long do AR 15 magazines last?

A: A well cared for AR15 magazine can last forever. Many believe that a loaded magazine should not be left like that for more than 6 months, but this is debated among experts if swapping out is necessary.

AR-15 Maintenance

Q: What is the life expectancy or lifespan of an AR 15? How long does an AR 15 last before it wears out?

A: The life expectancy of an AR15 (specifically the upper receiver which experiences the most distress) depends on the abuse and care. Small pieces on the bolt carrier group (BCG) may start to wear out before accuracy issues are noticed but an upper that is well cared for and cleaned regularly can serve for over 20,000 rounds and more.

Q: How often does an AR 15 need to be cleaned?

A: Because of the tight tolerances on an AR15, it should be cleaned after every use or at least once a month in general use. It will serve with less frequent cleaning and heavier use/abuse but failures to feed and eject may become apparent if allowed to get too dirty.

Q: How to keep an AR 15 from rusting?

A: To keep an AR15 from rusting you only need to focus on the steel parts which are the bolt carrier group (BCG) and the barrel. These are cared for by cleaning with an oiled rag and keeping in a dry storage place. The rest of the gun is plastic or an aluminum alloy.

AR-15 Accessories and Customization

Q: Where is the proper spot to mount a bipod on an AR 15?

A: The proper place to mount a bipod on an AR15 is as far forward as possible with the legs folding forward. This is done to provide space for other accessories, but also to give the widest base for stability.

Q: How long should an AR 15 sling be?

A: There is no solid answer to how long an AR15 sling should be: it is determined by body type, preference and use. The 54" length is a pretty standard length, but it really is dependent on your body type and carrying preferences. As to types, the typical sling that mounts front and rear is a two-point sling and a three-point has a strap running to a middle point connection, allows the rifle to pulled snug.

Q: Are AR 15 suppressors worth it?

A: Where legal, AR15 suppressors are worth it because of the ease of installation and the capability to use in ranges where unsuppressed use can be distracting to outright uncomfortable (AR15s are loud).

Q: Are angled Foregrips legal on AR 15 pistols?

A: At present (November 2022), per the most recent letter from the ATF, and angled foregrip is legal to install onto an AR15 pistol. Vertical grips are NOT legal and make an AR15 pistol a short-barreled rifle – requiring a federal tax stamp. The best way to tell the difference is if the supporting hand’s thumb can get behind the grip and the other fingers can wrap around – it is a vertical grip and not legal for a pistol.

Q: Do all AR 15 come with iron sights?

A: Not all AR15s come with iron sights. Some may only come with a fixed front sight and no rear sight and many are available with no sights at all (flat top) to use either iron sights or optics.

Q: How much does Cerakoting an AR 15 cost?

A: The cost of Cerakoting an AR depends on how much of the gun will be coated and how many colors or patterns. For cerakoting the upper, lower receivers and the handguard in one color can cost anywhere between $60-150 +/-

STNGR currently offers select handguard models & lengths in Flat Dark Earth (FDE) cerakote. Shoot us a message if you're going for a custom look and need a cerakoter recommendation. We know a guy.

What's the best AR-15 for ...?

Q: What's the best AR 15 for home defense?

A: The best AR15 for home defense would be small: a short-barreled rifle (SBR) or pistol with brace that is easy to maneuver within the close confines of doorways would be ideal. Consider also a suppressor (where legal). The concussive blast of a 5.56/.223 caliber round out of a short barrel is both thunderous and bright: in a closed area in the dark, the first round can be debilitating for anyone in the room – but training can mitigate the penalties for the user.

Q: Is an AR 15 too much for home defense?

A: The AR15 for home defense has bonuses such as being easy to manipulate, weapon mounted lights and/or laser sight, and decidedly potent stopping power. The obvious drawbacks are the size – a full length rifle may be difficult to maneuver within doorways, overpenetration through thinner walls and the noise. But the modularity of AR15 can mitigate many of these detractors.


Disclaimer: The information presented here is for general educational and informational purposes only. This information is not intended as legal or expert advice. Consult your local, state, and federal laws and published ordinances and www.atf.gov to ensure you are in compliance with the current local, state, and federal regulations.

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