Choosing The Best AR-15 Cartridge

So what is the best AR-15 cartridge?  Maybe you are looking to buy your first AR-15, or maybe you are looking for an alternate caliber to a rifle you already own.  There are a lot of caliber options for the AR-15 shooter right now.  They range from the ever popular 22 Long Rifle, to upper receivers designed to fire the 50 BMG.  How do you wade through the options and choose the best caliber available?

I don't think there is one hands down "best" AR-15 caliber.  But, if you read firearms forums and magazines you will see many claims to the contrary.  I think that many of the calibers serve specific purposes.  They may excel in certain circumstances, but not all.  In this article I want to take a look at some of the common calibers available, their uses, and why you don't have to settle for just one.  

Consider the role:

The first thing you need to think about when picking a caliber is the role of the rifle.  The rifle doesn't have to fit into just one role, but it may not be able to do all of them equally well.  Here are some of the typical roles you might consider for an AR-15:

• Target Practice/ Plinking
• Hunting
• Home Defense
• Precision Shooting
• Duty Gun

Look at the list above and pick out the categories that are most important to you.  This will be the starting point for determining what you will need the cartridge to do.  

Cartridge Class:

Next let's look at the cartridge class and what it does well.  We'll look at rimfire, handgun, standard, medium range, and big bore cartridges.  This discussion isn't meant to be exhaustive, but should give an idea of what is available and how certain rounds fit better in certain roles.

Rimfire:  Target Practice/Plinking, Small game hunting

The classic 22 Long Rifle is probably one of the most widely owned calibers in the world.  The ammo is easy to find at almost any sporting good store and is inexpensive compared to centerfire ammunition.  Rimfire has low recoil and is quieter than most other rounds, making it an easy choice to teach new shooters, especially young shooters.  I believe that every gun owner should own at least one 22.  While the 22 Long Rifle is great for target practice and small game hunting, it isn't suited for home defense or duty use when other options are available.  

An AR-15 in 22 Long Rifle is typically cheaper than other AR variants.  You can also purchase a separate upper receiver in 22 Long Rifle to go with a standard AR-15 lower receiver.  Buying a Ruger 10/22 would be cheaper than an AR-15, but if you already shoot the AR in another caliber it gives you the option of low cost practice ammo on the firearm platform you want to train with.  

Handgun Calibers:  Target Practice/ Plinking, Limited Hunting, Home Defense

9mm home defense ammo

Next up are ARs built in handgun calibers.  I built an AR pistol in 9 mm for cheaper range practice.  Check out the post on it here. Calibers such as the 9 mm  40 S&W, and the 45 ACP bring common pistol loadings to the AR-15. The advantages of a pistol caliber AR are several fold. The first is the cost of ammo. Pistol ammo, especially when purchased in bulk, can often be cheaper than some of the more exotic calibers. It is also easy to find pistol ammo at your local Walmart or sporting goods store. Depending on the lower receiver that is used, some pistol caliber rifles even use common pistol magazines, such as Glock magazines.

Pistol caliber rifles offer the ability to use the same ammunition as your handgun, plus they tend to have lower recoil and noise than a full power rifle round. If you reload, you may be able to use lead bullets in your rifle, lowering the cost of ammunition even more. You may have to check your states hunting laws to determine if you can hunt with a pistol caliber rifle, but in many locations you can. The rifles work well for home defense as well. The longer rifle barrels provide increased stopping power compared to pistol length barrels.

The Standard AR-15 Cartridge: Target Practice/ Plinking, Hunting, Home Defense, Precision Shooting, Duty Use.

The standard, most common AR-15 caliber is the 5.56mm/ 223 Remington.  While I won't get into the differences or variations right now, this standard military loading is the most commonly used caliber in the AR-15.  From the military to law enforcement, the 5.56mm round has seen it's fair share of combat.  While you can find people that are both for and against it, it will probably be the most common choice for a long time to come.  

Because of use by the military, law enforcement and so many private individuals, 5.56/223 ammo is some of the cheapest rifle ammo you can buy.  It is often sold at smaller sporting good stores and Walmart.  There are ammo options ranging from basic, inexpensive loadings to high end, precision loadings.  Many states allow the use of 5.56/223 rifles for hunting, but make sure you check the regulations before buying one for hunting.  It is also the the prime candidate for NRA Highpower competitions.  

Medium Range: Hunting, Home Defense, Precision Shooting, (Possible) Duty Use.

300 Whisper with 208gr AMAX bullet

The next class of cartridge I have decided to call "Medium Range."  This can include cartridges such as the 300 Whisper/Blackout, 6.8 SPC, 6.5 Grendel and other similar cartridges.  These loadings tend to offer heavier bullets than a 5.56/223 can provide, but at slower velocities.  They are typically limited by the fact that they have to be loaded to an overall length that is compatible with a standard AR-15 magazine.  

These cartridges were designed to improve the terminal ballistics of the 5.56/223 at longer range.  For that reason they tend to do well for home defense, duty use, and hunting.  Not only are the terminal ballistics improved for hunting, but the larger calibers makes them more likely to be allowed by your state's hunting regulations.  There are also rifles built in less common calibers such as the 6mmBRX that are quite the tack drivers.

One disadvantage of this class of cartridge is the cost and lack of availability of ammo.  Although most of the ammo is considered "premium" ammo, it comes with a price to match.  There are a few cheaper alternatives available for those that are willing to seek them out.  Another issue is availability.  I own a 6.8 SPC and there are very few local places for me to buy ammo.  That isn't a huge concern for me, as I reload, but if you buy factory ammo you may want to find out what is stocked locally, or buy in bulk when you find a good deal online.  

Big Bore:  Hunting, Home Defense

450 Bushmaster loading from Hornady

The last category I want to look at are the big bore loadings.  The three most commons are the 450 Bushmaster, 458 SOCOM and the 50 Beowulf.  These rifles fire big, heavy bullets when compared to the puny 5.56/223.  These loadings bring true knock down power to the AR-15 platform, requiring no more changes than a barrel, bolt and possibly a different magazine.  Although they may not have the range of the medium range cartridges listed above, they can provide plenty of knock down power at reasonable ranges.  

The biggest disadvantage of these rounds is the cost.  While I have seen 450 Bushmaster ammo for as little as $23.00 per 20 rounds, they tend to cost more.  If you reload you can use a wide range of bullets to bring costs down, but that may be limiting to those of you that buy factory ammunition. 

So Which Cartridge Is Best?

So which cartridge is best?  You'll notice that I didn't really answer that, which was intentional.  I own at least one AR in each category except for the rimfire and that's because I already have a 10/22.  They each have their own purpose and you have to look at how you want to use it.  

I do believe that the 5.56/223 makes a great first AR-15.  The ammo is easy to find and inexpensive.  It can be used for target practice, plinking, home defense, duty, and in some cases hunting.

What is your favorite AR loading?  Let me know in the comment section below.  I just scratched the surface with some of the more popular loadings, there are many, many more available.