January 29, 2019
By G&A Online Staff
The popularity of the AR is problematic for anyone looking to purchase one of these rifles. There are so many types at a wide variety of price points that it’s difficult to know what AR works best for any particular application. Since the answer is so often “general use,” this review highlights the FN 15 Tactical II.
Other than Colt, FN is the only manufacturer that can claim they’ve made ARs in large quantities for the U.S. military. That fact matters because it means the company has a track record of producing rifles that meet required battle-ready performance specifications.
Perhaps the two most important parts of any AR-type rifle are the bolt and the barrel. Both have to be made from quality materials and manufactured to offer performance and long life. The Tactical II offers both in the FN 15’s critical components.
FN knows a lot about making bolts for ARs after decades of making M16s for the military. Made of the steel alloy Carpenter 158, FN’s bolts undergo rigorous quality control and testing to ensure long-lasting dependability. One Tough Bolt
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FN has produced bolts for so long that they know how to make them correctly. If they didn’t, they would have quickly lost their military contracts. In the creation of the bolts, FN follows all of the specified handling protocols of magnetic particle inspection (MPI), peening, pressure testing, etc.
AR-pattern bolts have two lugs that are prone to break under very high use (i.e., after several thousand rounds fired). The two lugs opposite the extractor are only supported on one side, so they are usually the first to break. One way to get to prolong their life span is to use a steel alloy, either Carpenter 158 (the military’s specified material) or 9310, and to get the heat-treat process correct.
FN uses Carpenter 158 for its Tactical II bolts. However, heat-treating a small part like a bolt is difficult. Carpenter 158 steel was originally intended for large industrial gears. It is very tough, but it is remelted steel made from a process that uses two large electrical probes to burn excess sulfur and phosphorus out of the material.
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Removing the sulfur and phosphorus from the steel alloy gives it a very predictable wear cycle, which is why Carpenter 158 is one of the recommended materials. Unfortunately, the absence of those materials makes bolts difficult to correctly heat-treat. Small variations in soak time and temperature can mean the difference between a part that lasts almost forever and one that breaks after a thousand rounds. But FN did it right, and their bolts can be depended upon.
Barrel Up
FN’s three-pronged so-called “European” flash-hider is similar to the type used on many FN SCAR rifles. The barrel FN uses on the Tactical II is the preferred length (16 inches) and type for the most common general-use AR. Most inexpensive ARs use button-rifled barrels because they are easy and inexpensive to make. FN chooses to use hammer-forged barrels instead.
Any AR barrel should be able to handle a lot of rounds in a short time period and survive this tempo for several years. Hammer forging a barrel is very helpful in this regard. The process of making a hammer-forged barrel involves first inserting a mandrel through the center of a short, thick cylinder of steel. Hammers then beat the steel until it takes the shape of the finished barrel. This usually means the barrel is twice as long as the cylinder that started the process, so it has undergone significant pressure.
All that pressure gives this type of barrel a couple of very useful characteristics. The bore will be a mirror copy of the mandrel, so the internal and external dimensions are very precise and the rifling is exact. In inexpensive button-rifled barrels, that process can have irregular rifling because the button can slip when pulled through the bore.
Another significant advantage of hammer-forged barrels is the work-hardening that occurs during the manufacturing process. As those hammers beat the barrel into shape, the portion that sits directly against the mandrel gets very hard because it cannot move. Every time the hammer strikes, it squishes the barrel material up against the mandrel making it harder. This is a very useful phenomenon when talking about barrel bores. The harder the bore, the longer it will last because it can better resist the heat and pressure that comes when firing cartridges. FN has made hundreds of thousands of these barrels over a few decades and has long since perfected the process.
System Foresight
The 13-inch, octagonal handguard provides a full Picatinny rail aligned with the flat-top receiver and ample M-Lok slots for adding accessories. In keeping with the ideal AR theme, FN had the foresight to put a mid-length gas system on this rifle. Stretching the length of the gas tube that runs atop the barrel means the bullet has to move further down the bore before the action cycles. When the bullet moves down the barrel, the pressure inside the bore drops. A longer gas tube means lower operating pressures.
ARs are happiest when pressures are low. Residual pressure in the chamber makes it hard for the bolt to twist to unlock and is the prime reason why bolts break. Lowering the pressure in the bore adds a lot of life to the bolt by making it easier for it to unlock and extract the fired case. There is no good reason to have the shorter carbine-length gas system on a 16-inch barrel. Mid-length is always the right answer.
Whether or not an optic will be used on a general-use AR, a good set of backup, flip-up sights are a must. Getting a Grip
The handguard found on the Tactical II is absolutely one of the best factory types made. It is 13½-inches long and beautifully machined. There are no sharp edges on it anywhere and the octagonal shape sits comfortably in the hand. Three of the eight sides are flat enough for M-Lok slots — U.S. Special Operations Command’s preferred attachment method — and help keep the rifle oriented in the support hand.
Besides having a Magpul MOE pistol grip, the rifle’s triggerguard is shaped to better fit the firing hand’s middle finger while providing enough room for a gloved finger. The rifle also features Magpul’s MOE grip and enhanced triggerguard. The grip is comfortable and the triggerguard protects the firing hand’s middle finger by filling the gap normally present between the triggerguard and grip, while also accommodating a gloved trigger finger.
Farther back sits the adjustable Magpul MOE SL buttstock. It has a slender profile that puts plenty of meat against the firing shoulder. Its adjustment lever is tucked out of the way where accidental activation is unlikely. There is a metal flush cup on either side of the stock for use with quick-detach sling swivels and two locations where the sling can loop around the stock for direct attachment.
The sturdy Magpul MOE SL adjustable stock can alter length of pull from 11 inches to 14 inches. Magpul is also one of the very few companies that beats the brakes off their products in testing. The MOE Slim Line (SL) buttstock is so durable that you could extend it and then repeatedly slam it to the ground without breaking the stock. It is highly likely that the positioning detent in the buffer tube will deform before the stock breaks. The SL is a fantastic addition and should be a serious consideration on other AR-15s as an aftermarket accessory.
Ideal Execution
Performance at the range was about what you’d expect from a quality hammer-forged, free-floated barrel. Five-shot groups at 100 yards hovered right around 1 MOA, which is above-average performance from any AR.
Notes: Accuracy is the average of five, five-shot groups at 100 yards. Velocity is the average of five shots recorded by a LabRadar chronograph adjacent to the muzzle. FN got the details of this rifle right. They kept weight down with an excellent choice in barrel contour and then used a hammer-forged tube to get maximum life. All of FN’s tribal knowledge went into making sure they got the manufacturing details right as far as dimensions and heat-treat are concerned.
Finally, FN made sensible choices on the furniture and handguard. There is no excess anywhere on the FN 15 Tactical II, but it absolutely has every relevant feature you’d want or need on a general-use, AR-pattern rifle.
FN FN15 Tactical II fnamerica.com
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