When I was trying to build my first AR-15 I had no idea what options were out there. I just assumed everything was 5.56 NATO. However, the best thing about the AR platforms is that they are incredibly customizable. This means that you can take MOST of the same parts and just switch out a few things and have a completely different experience.
I suggest, if you are in the market to buy an AR-15, do your research on caliber first. You may have a specific use case in mind, like hunting or self defense, and one caliber may suit those need better than another. However the most important thing is that no matter the caliber, make sure you are buying a quality gun, you spend the time to get comfortable and train with it, and that you are safe.
Here is a cheat sheet for caliber options that I wish I had when I built my rifle.
This is only for the AR-15 platform, not the AR-10.
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
None – Mil Spec AR-15 is all you need.
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
Barrel – You will need a 5.56 NATO barrel.
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
Barrel – You will need a .223 Wylde barrel.
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
Barrel – You will need a .300 BLK barrel.
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
Barrel – You will need a .458 SOCOM barrel.
Bolt – You will need a .458 SOCOM BCG.
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
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.
Like most things, finding the best AR-15 caliber option depends on your intended use. I suggest at a minimum going with a 5.56 NATO caliber rifle. 5.56 is able to shoot both .223 Remington as well as 5.56 NATO but the opposite is not true.
If you are looking for a short range, suppressed rifle for self defense or tactical situations, the .300 Blackout is increasing in popularity and is one of the most successful new calibers in the last 5 years.
If you are looking to hunt mid to larger game, the 6.5 Grendel is great option for a round that travels similar to a 5.56, but with a much larger bullet.
Ultimately, it is up to your needs. There are a lot more options available to you, but start thinking about your intended use and build a rifle to fit those needs.
Welcome to Guns
