AR-15 Caliber Options: Which is Right for You?
When I was looking at building my first AR-15 I honestly didn’t even think about what AR-15 caliber options were out there. I just assumed I was going to build a 5.56 NATO rifle. After doing a bit of research I ended up going with a .223 Wylde build.
If you are going to be buying an AR-15, no matter the caliber, make sure you are buying a quality gun. For my next rifle, I am going to buy the .300 Blackout Radian Model 1.
Every caliber has a different use, and before you settle for .223 Remington, make sure that you understand your options.
AR-10 vs. AR-15
First off, in this article I am only going to be talking about the AR-15 caliber options available. I also have a complete guide to AR-10 caliber choices.
There are a lot of similarities between AR-10s and AR-15s; however, the biggest difference is in the size of the rifle, the thickness of the barrel, and the ability to shoot larger rounds.
Because of the thickness of the barrel and the increased size, the AR-10 is able to be chambered in larger rounds such as 7.62x51mm NATO, .308 Winchester, .260 Remington, 6.5 Creedmoor, and .300 Win Mag.
What factors should you consider?
Barrel Length
Barrel Length is an easy way to determine whether or not you are going to need a .300 Blackout or not.
5.56 NATO and .223 Remington are optimized for a 20 in barrel, and can be accurately fired down to a 10.5 in barrel. However, as you deviate from the ideal, you sacrifice effectiveness.
For anything shorter than 10.5, I would recommend going .300 Blackout. .300 Blackout can be effective even down to a 6 in barrel.
This means that if you are going to be running a tactical SBR or pistol, or want a gun with suppressor in the handguard, or are looking for maximum maneuverability, the .300 Blackout will fit those needs.
Power and Distance
There are a lot of factors that you can geek out on when it comes to ballistics and trajectory. My dad loves long distance shooting and spend countless hours testing different powders to optimize his shooting.
However, for the casual/mid level shooter, the biggest factors for performance are going to be speed, weight, and drop.
There are lots of different AR-15 caliber options on the market. Each one has strengths and weaknesses, but don’t spend too much time looking for the “perfect” round.
There is no such thing as the perfect round.
In most cases, get a rifle for a specific use or task, and start training. Then get another rifle for another task.
Each caliber also has a range of ballistic and speed options available. Reloading your ammo can give you even more options. Find something for you intended use, and start practicing.
Ammo Availability
A rifle is basically useless unless you have ammo. I mean, I guess it makes for a heavy club, or light mount. However, in most situations, you are going to want ammo.
Unless you are reloading all your own ammo, and have found a stockpile of bullets and powder, choose a caliber that is more available.
Some of the “specialty” calibers available are great, but if you can’t ever find ammo, then you can’t train. And training and being comfortable with your rifle should be the most important factor when looking at AR-15 caliber options.
.223 Remington
Specs
Weight – 35 to 77 grain
Muzzle Velocity – 2700 to 3800 fps
Effective Range – 600 yards
Drop At 300 Yards – 5 to 9 in
Drop At 400 Yards – 17 to 25 in
Minimum Barrel Length – 10.5 in
Caliber Specific Parts
None – Mil Spec AR-15 is all you need.
My Take
It is important to note that all 5.56 NATO rifles can safely shoot .223 Remington ammo, but not the opposite. The biggest difference between the two rounds is pressure, and a .223 caliber barrel isn’t rated for enough pressure.
The .223 Remington round is a great round for deer and small animals. Not only that, but is a great self defense and range round.
It is one of the most common rounds available which makes stockpiling ammo easy.
If you are interested in .223 I would recommend just getting a 5.56 caliber rifle because it gives you more flexibility.
5.56×45 NATO
Specs
Weight – 35 to 77 grain
Muzzle Velocity – 2500 to 3600 fps
Effective Range – 500 yards
Drop At 300 Yards – 5 to 9 in
Drop At 400 Yards – 17 to 25 in
Minimum Barrel Length – 10.5 in
Caliber Specific Parts
Barrel – You will need a 5.56 NATO barrel.
My Take
5.56 NATO is the military version of the .223 Remington. It is rated for a higher pressure rating and has a slightly longer “freebore”.
The “freebore” is the diameter of the section between the chamber and the rifling in the barrel.
5.56 NATO has a slightly larger “freebore” to deal with the increased pressure. This creates a slightly looser fit between the bullet and barrel. This can lead to very small accuracy inconsistencies.
.223 Wylde
Specs
Weight – 35 to 77 grain
Muzzle Velocity – 2700 to 3800 fps
Effective Range – 700 yards
Drop At 300 Yards – 5 to 9 in
Drop At 400 Yards – 17 to 25 in
Minimum Barrel Length – 10.5 in
Caliber Specific Parts
Barrel – You will need a .223 Wylde barrel.
My Take
Bill Wylde created .223 Wylde in order to be able to shoot both 5.56 NATO and .223 Remington without sacrificing any of the accuracy, velocity, and distance that you lose with 5.56 NATO.
The biggest differences in .223 and 5.56 is the “freebore” and the pressure rating.
.223 Wylde takes the advantages of both systems and brings them together. This means you get a shorter “freebore” while still being rated for higher pressure rounds. I am a big fan of my .223 Wylde build.
.300 Blackout
Specs
Weight – 110 to 250 grain
Muzzle Velocity – 1000 – 2400 fps
Effective Range – 300 yards
Drop At 200 Yards – 6 to 35 in
Minimum Barrel Length – 6 in
Caliber Specific Parts
Barrel – You will need a .300 BLK barrel.
My Take
.300 Blackout was designed to be shot suppressed. So if you are looking at this caliber, make sure to get a suppressor with it.
If you are thinking about home defense, it is important to know remember that the .300 BLK has a lot more penetration power than a 5.56 NATO round. Meaning, if you miss, you run the risk of going through multiple walls and causing unintended damage.
The other downside is price of ammo. The .300 BLK is significantly more expensive to shoot and reload than a 5.56 NATO or .223 Remington. If this is a factor in your training, then it is important that you choose a chamber that you can practice with.
However, the .300 BLK has been one of the fasting growing rounds in the past 5 years for a reason. It was made to shoot subsonic, and it is allows you to have a much shorter rifle.
This gives you maneuverability and tactical advantages, but it is important that you know the good and bad with each caliber.
.458 SOCOM
Specs
Weight – 250 to 600 grain
Muzzle Velocity – 1000 – 2100 fps
Effective Range – 250 yards
Drop At 200 Yards – 11 to 30 in
Minimum Barrel Length – 6 in
Caliber Specific Parts
Barrel – You will need a .458 SOCOM barrel.
Bolt – You will need a .458 SOCOM BCG.
My Take
Need an even bigger bullet than the .300 BLK? Enter the .458 SOCOM.
For size comparison, the .300 BLK will still give you the standard 30 rounds in a AR-15 magazine, but the .458 SOCOM will only fit 10 rounds in the same magazine.
The .458 SOCOM also has significantly more recoil because it is pushing a much larger bullet.
6.5 Grendel
Specs
Weight – 120 to 139 grain
Muzzle Velocity – 2500 – 3000 fps
Effective Range – 700 yards
Drop At 300 Yards – 8 to 14 in
Drop At 400 Yards – 25 to 30 in
Minimum Barrel Length – 14 in
Caliber Specific Parts
Barrel – You will need a 6.5 Grendel barrel.
Bolt – You will need a 6.5 Grendel BCG.
Magazine – You will need a 6.5 Grendel Magazine.
My Take
The 6.5 Grendel is a caliber that I would look into if you are building a rifle primarily for hunting medium to large game.
This round gives you similar distance, speed, and drop to the .223 Remington round; however, it is able to do that with a much larger bullet.
This gives you significantly more ballistic power at distance. So if you are going to be hunting wild boars or deer, the 6.5 Grendel could be a good option for you.
AR-15 caliber options, what should you choose?
Like most things, finding the best AR-15 caliber option depends on your intended use. The best thing about the AR-15 platform is that you can customize the rifle completely to your needs.
If this is your first rifle, and you just need to train and get rounds down range; I would recommend a 5.56 NATO or .223 Wylde. However, if you are building a new rifle for a specific scenario, take a look at some of the options out there.
