What Are The Most Common Barrel Profiles For The AR-15?

If you’re new to semi-automatic rifle ownership, the odds are that your first acquisition will probably be an AR15 semi-automatic rifle with a standard barrel in the upper receiver. Although your rifle’s barrel may provide years of dependable range shooting or hunting trips, it’s highly likely that eventually, you’ll want to upgrade or modify your AR15 to get improved reliability and performance. 

However, before swapping barrels, you need to understand what benefits you hope to achieve with a newly installed AR15 barrel. There are plenty of standard options available on the market, and each will provide a certain number of improvements and, at the same time, some fundamental drawbacks you’ll want to avoid. This list of typical barrels for AR15 rifles will undoubtedly help when it comes time for your pick.

M4 and Government A2

Two most standard AR15 barrels on the market today is the M4 profile and the classic A2 or Government profile barrels. While both are similar in functionality and form, the primary difference between the M4 and A2 profile barrels is that the M4 has a channel on its side for mounting an M203 grenade launcher.

Of course, on a routine day at the range for any recreational firearm enthusiast, it’s unlikely the range master is going to allow an opportunity to lob a few grenades at a downrange target. Aside from a more tactical difference, both barrels possess the same dimensions and features. Rumor has it military members often used the tip of the original A1 barrel as a pry bar which resulted in a bent and unusable barrel. Although unverifiable, the rumor did prompt the creation of the A2, a heavier barrel that could withstand harsh use in the field. This industry standard AR15 barrel narrows down to approximately .625 inches after the chamber, then flares to .75 inches at the gas block up to the muzzle.

One benefit and, at the same time, a drawback of this type of barrel is the added overall weight supposedly assists reduced muzzle flip during a rapid-fire situation. While it may help with muzzle flip, the additional weight of almost eight ounces or more means you’re carrying around a front-heavy rifle. Although it may not sound like much, the extra weight will be noticeable during rapid deploy operation or when in the field for hours or days at a time.

HBAR Precision Barrel

Another typical heavy-profile barrel you’ll often see on the market is the HBAR barrel. This heavy barrel automatic rifle or HBAR barrel not only has the extra weight at the back, but it’s much thicker at the rear. The primary reason for this type of manufacture is to mitigate excessive heat near the gas block, which is beneficial if you love to dump a few magazines rapidly at the range.

However, the HBAR is better suited for precision shooting. The additional material from the chamber to the gas block means the barrel is much slower to heat up, which slows a potential shift in barrel alignment due to deformation caused by higher temperatures. For a precision shooter that depends on the accuracy of each shot, the last thing needed is a lack of precise placement due to a barrel that could potentially shift because of heat.

Heavy Fluted Barrel

Another favorite barrel for the precision or competition AR15 owner is a heavy fluted barrel profile. Like the A2 or HBAR types of AR15 barrels, these barrels have a similar commonality: they’re a much heavier barrel. While both the benefits and disadvantages of a bull barrel are the same as the A2 or M4 barrel, the sole purpose and reason for modifying your AR15 with a heavy fluted barrel is to maintain more precise shots for longer.

Most bull barrels have extra mass, which stiffens the barrel sufficiently and reduces heat to allow better dependable and more accurate shots. In addition to the heavier mass, they are fluted to help dissipate heat even further allowing the barrel to cool much faster. Popular with competition shooters, as the weight is not as important as accuracy.

Pencil Barrel

The original barrel explicitly created for the AR-15/M16 rifle represents a much lighter barrel for any weight-conscious AR15 owner. Initially designed by Eugene Stoner, Jim Sullivan, and Bob Fremont, the original pencil barrel was only 0.625 inches from the front of the barrel to the back, with a slight bulge in the middle and represented the lightest and most dependable AR15 barrel on the market at the time. Unfortunately, back then, the technology of stress relief and heat treatment hadn’t advanced to the degree it has nowadays.

With the inception of the pencil barrel came instances of heat warp, also known as elastic deformation, causing the barrel to shift its point of impact. While today’s pencil barrels aren’t as affected as the original pencil barrels were, remember that any standard barrel will move its point of impact when it suffers enough consistent heat.

SOCOM Barrel

For the new enthusiast who is just beginning to enjoy the world of recreational shooting or hunting with an AR15, you may have heard the word SOCOM when your companions are talking about their newest barrel modification.

Simply put, SOCOM stands for Special Operations Command and represents a higher standard of stringent requirements generally approved for military use. Although many barrel manufacturers refer to their SOCOM barrel as a Mil-Spec barrel, you should do a little extra research before purchasing to ensure you get a product priced because of the features it provides and not just its name.

A proper SOCOM barrel is a full-on reverse of the M4/A2 AR15 barrel. The barrel of a SOCOM is thinner once past the gas block and then thicker from the chamber to the gas block. While most SOCOM barrels feature a slot for mounting an M203 grenade launcher, a SOCOM barrel represents something heavier and sturdier than a pencil barrel but not as bulky as an M4/A2. If you need a “between” barrel that will hold up to several bouts of sustained shooting but need a reduction of overall weight, you may want to consider a SOCOM barrel for your rifle.

The Best of the Rest

While today’s market has many other types of barrels, such as those in the fluted or custom contoured variety, these barrels previously mentioned represent the lion’s share of typical barrels you’ll find in an AR15. When choosing one, the best thing you’ll need to do initially is to decide what benefits are the most important to you, then do some research before buying and modifying.