The AR-15 is America’s rifle, at least for the moment. Everyone should own two. We have been using 5.56/.223 in this gun for over 40 years and like it or not it is combat tested as the day is long. One of the top questions I get when people go to buy their first AR is, “What barrel length should I get?” Fear not dear readers, for I have an opinion on this. And right after, I will give you the details on a foolproof Middle East success strategy.
If you shop hard enough, you can find barrel length options from 7 inches all the way to 36 inches, which is pretty insane. For the purpose of our new buyers though, it is pretty safe to talk only about the 11-inch up to 20-inch versions. They are the most common.
Just like your mom, I am not a fan of short barrels. The big drawback to shorties is the loss of velocity, which I have elaborated on in a previous video. In a nutshell, every inch of barrel you cut off, up to the optimal length that is generally considered to be 24 inches, you lose pressure and have incomplete powder burn. This means your bullet leaves the barrel with less speed and as it bleeds off speed during flight it rapidly enters the zone of “sub optimal terminal effect.” That means it won’t kill something worth a damn. And whomever you shot will be mad at you, in addition to probably taking it personally. However, that aside, any barrel under 16 inches is governed by special ATF rules. Putting a short barrel on an upper receiver not registered as an SBR is illegal. It’s dumb, but them’s the rules.
What if you really want a MIL-SPEC 14.5-inch barrel? That’s what all the ninjas use, it must be the heat right? Well, no not really. How the DoD decided on 14.5-inches, I have no idea. But they did. If you insist on a 14.5-inch barrel, you can actually still have it with no special tax stamps and government permission slips. The trade off is, it has to have a flash hider that makes it 16 inches overall, and that flash hider must be permanently attached. This is commonly referred to as “being pinned and welded.”
A gunsmith actually drills a hole through the flash hider and into the barrel, inserts a pin, and then welds the hole shut. For all practical purposes, it’s not coming off after that, ever. You can cut it off, but then you have a 13.5-inch barrel. And for the labor for removing it properly, you could buy a new barrel. So what exactly is the problem? No room for growth. You might be happy with this exact setup today, but you won’t always be. Suppressors? You are going to need a new barrel unless you bought the flash hider specific to the brand of suppressor your future self wants. Competition muzzle brake instead of flash hider? New barrel. New gas block and handguard? More than likely, new barrel. To me, this argument alone puts anything below 16 inches out of the equation.
So that leaves us 16-, 18-, and 20-inch barrels. Twenty-inch barrels are becoming less and less common, with some exceptions like the FNH M16A4 copies on the market right now. Nothing wrong with a 20-inch; it will give you some more punch in the velocity department. All of us former Jarheads have carried them around a bunch. They work fine. My only complaint about a 20-inch is that they don’t feel as balanced in your hands. Plus that extra 2 inches over the 18 creates some silly limitations. My truck door won’t close with a 20-inch under the seat. It’s harder to conceal them in a backpack or other carry bag. There are fewer case options. And not that I am a slave to fashion, but a 20-inch looks retarded with a collapsible stock on it.
Now we’re down to the 16 and 18. The 18-inch will shoot a bullet faster but at a cost of added weight and size. The real question is, how much faster? I was kind of surprised by the answer to this. The 55 grain was the lightest bullet I tested, and probably the most common round available. In my two guns, there was only a difference of 110 feet per second between the 16-inch and the 18-inch. With 69 grain ammo, the difference was down to 75 feet per second. That doesn’t make a lot of difference in bullet drop at range. I can understand why a light sniper rifle would go with the full 18-inch barrel, to squeeze every ounce of velocity and reach out of the gun. But for a general purpose rifle, that isn’t enough for me to renounce the 16-inch.
How about barrel profile? Does the thickness of the barrel really matter? Usually, it does. The thickness of your barrel generally increases rigidity, which directly affects how well your gun shoots. There are many other factors, not least of which is how it was cut, but all other things being equal, a more rigid barrel shoots tighter groups. The thickness of the barrel also dictates how long it takes the barrel to heat up, which generally also decreases accuracy until that barrel cools back down. A thin barrel heats up faster, and a thick barrel takes longer to cool off.
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