What first caught my eye about the Faxon Firearms 5.56mm stainless steel pencil barrel was its ridiculously light weight. I blinked, looking at Faxon’s website’s at the stated barrel weight of 1.19lbs – just over 19 ounces. That couldn’t be right; my pencil-profile 14.5” middy weighs 21 ounces. So I called up the folks at Faxon and asked if their website was accurate or just a typo. They assured me the data was correct, and as soon as the barrels were back in stock, I ended up with one on my doorstep.

This barrel is so thin it looks anorexic. It’s so lean that it makes you wonder if it’s safe to shoot (spoiler alert: it is). The difference between the Faxon profile and even a standard pencil barrel is dramatic. With this barrel installed on my carbine (replacing a SPR-profile 16 inch that weighted 35 ounces), my carbine feels phenomenally light. I love the reduction of weight up front.

Faxon pencil barrel

Top to bottom: 16 inch medium heavy barrel, M4 profile, 14.5″ pencil barrel, Faxon’s incredibly light pencil barrel

Now let’s talk about the term “pencil”profile. In comparing this barrel to other lightweight profile barrels, I feel that the term is simply not sufficient. “Pencil” is commonly used by other companies to refer to .625″ gas block barrel designs. The Faxon barrel is different. Daniel Defense’s 16″ lightweight is 2.5 oz heavier. A lightweight BCM barrel is 4 ounces heavier than the Faxon pencil profile barrel. Even BCM’s Enhanced Lightweight Fluted barrel is 2.5oz heavier than the Faxon counterpart.

How did Faxon come up with such a lightweight barrel? In a flash of insight, they went back to the original Colt SP1, which had an ultra-lightweight barrel. Remember that throughout the Vietnam war, gas blocks with a .625” diameter were standard. Since these dimensions obviously worked well for Colt fifty years ago, Faxon engineers took the dimensions of the SP1’s 20-inch barrel and reverse-engineered it to make a 16 inch mid-length modern wonder.


It’s worth mentioning that the Faxon barrel is the cheapest of all those mentioned above. It’s almost a hundred dollars less than the Daniel Defense barrel, even though the Faxon is more expensive 416 stainless steel, compared to the DD’s chrome moly vanadium steel. As well, the DD model has A4 feed ramps, while the Faxon utilizes M4 ramps, which I prefer anyway. The BCM Enhanced is made from CMV steel and is chrome lined as well. Instead of chrome lining, I’m a big fan of ballistic nitride (QPQ, Melonite) treatment. All of my AR-15 barrels are QPQ treated, and the Faxon Firearms addition to my collection is no exception. If you don’t know much about QPQ, be sure to look at one of my previous articles on the subject.

Lightweight barrel chart


The first thing I noticed when I shouldered the rifle was how quickly it came up to my shoulder. The reduction of 20oz off the front-side, was so dramatic that I actually had to stop myself from super-elevating the barrel, as I pointed it downrange. For those of you who like the C-clamp stance for close-range shooting, the lightness of this barrel makes it less tiring on your support hand.

The reduction in weight made itself apparent in another way; recoil. The backward force into my shoulder was definitely greater than with a standard barrel, though not enough to cause distraction. A muzzle brake would certainly lessen the recoil, but I intend for this to be my main fighting carbine. The muzzle flash from the Surefire muzzle brake I had on another upper would light up a half-acre during night firing. So I’ll keep a standard A2 flash hider on this barrel, simple and very effective at night.


I will say that I’m very surprised by the accuracy of M855 green tip out of this barrel. I have managed to get 1.5 MOA groupings at 100 yards. I was quite surprised by this, as the steel penetrator in the M855 nose makes it less accurate than other cartridges. In fact, this is probably the best accuracy I’ve sen from such a round in anything other than a Lilja barrel. Since the Lilja barrel cost several times what the Faxon does, I am indeed impressed.

Switching to 55gr FMJs, I was able to duplicate the groups, as long as I keep the rate of fire down to a low crawl. Anything approaching rapid fire results in a dramatic increase in group size.

Faxon Pencil Barrel - M855

The first seven shots were clustered in a 1.4 inch group. However, as I got impatient and let the barrel heat up, the subsequent rounds opened up the group significantly.


And that’s the Achilles heel of this barrel; heat. It’s really a function of physics that thinner barrels will heat up faster than thicker ones. When the Faxon pencil barrel heats up, the groupings expanded from roughly 1.5 MOA to 4.25 MOA with M855 and to 3 MOA with 55gr. This isn’t really bothersome, but the barrel does heat up fast.

On the flip-side, a thinner barrel will cool faster.


The lightness of this barrel provides for excellent portability, which is a factor if you’re going to be carrying your carbine a lot. The lightness eases weapons manipulation and only increases felt recoil slightly. The accuracy with standard ammunition is much greater than expected, especially for the first round or two in a string. Heat is an issue, even more so in this barrel than in other “lightweight” barrels on the market. However, even with a hot barrel, the accuracy still roughly met the 4MOA combat standard of the M4 carbine.

Next, we will look at 77gr and 69gr loads to see if this anorexic barrel really can consistently produce the hallowed 1 MOA group.

-By Allen Cosby

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53GR is an avid shooter, hiker and tinkerer. Introduced to guns at an early age, the hobby became a passion in his early twenties. After two years in Iraq as a contractor for a defense company, he developed an unhealthy addiction to military surplus gear. Though he's currently in treatment, the prognosis is that the condition is chronic.

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