The Real Deal

FN’s M4 And M16 Military Collector Series

By Holt Bodinson

Once upon a time, we could freely buy modern US military surplus firearms. We could buy Krags, 1903’s, ’03-A3’s, 1917’s, M1 Garands, M1 Carbines, even National Match 1911’s. That all ended for the most part during the Vietnam War era when the M14 and the M16 sported select-fire switches.

To their credit, Springfield Armory and Colt picked up the slack with semi-automatic versions of the M14 and M16 using a mixture of original GI mil-spec parts and aftermarket units, but they weren’t totally the real deal. FN America, the current government contractor for the M4/M16 military family of firearms, just changed the game with the production of exacting, mil-spec, semi-automatic versions of the issue M4A1/M16A2. These are the real deals.

Labeled the FN15 M16 Collector Rifle and the FN15 M4 Collector Carbine, both models are identical to those currently delivered to the military with the exception that the lowers lack an automatic sear assembly nor are they machined to accept one. Yet, for kicks, the stops on the ambidextrous selector switch are labeled: “Safe,” “Fire” and “Auto.” Pretty cool.

The term “mil-spec” covers a lot of territory. Essentially, it’s a standard of materials, dimensions & manufacturing processes. Its roots are thoroughly military and historically go back to the latter half of the 18th Century when the need to produce artillery with uniform dimensions and massive amounts of small arms with interchangeable parts was recognized. As better metal shaping tools evolved and accurate gauges were developed, “mil-spec” changed from being a possibility to being a reality.

One little sign of “mil-spec” can be seen on the bolts of the FN’s. They are marked “HTP/MPI” standing for “High Pressure Test/Magnetic Particle Inspected.” In short, after a proof cartridge has been fired in the bolt/barrel assembly, the bolt is inspected for any defects and then marked as tested. Another sign is the “UID” label attached to the magazine well. This “Unique Identification” label is a requirement of the DoD to give various military articles a unique ID to facilitate inventory control and tracking.


Holt’s favorite—the M4 carbine with 14.5-inch barrel (extended to a legal
16 inches with a permanently attached flashhider).


FN’s FN15 M4 and M16 are exacting, semi-auto copies of the real deal
issued by Uncle Sam (except for the select-fire switch!).

If you really want to dig into “mil-spec” data, go to, which gives you access to 55,000 Military, DoD, NASA, DoE and government specifications and standards. The data available on that site will more than satisfy your curiosity for a lifetime.

The current M4A1 and M16A2 models reveal the evolution these models have gone through over the decades. In my opinion, the most radical change has been in the development and application of the Mil-Std-1913 rail system which made possible the adoption of advanced optical sighting devices and made room for lasers, designators, lights and other invaluable accessories.

The familiar Mil-Std-1913 Rail was designed in the late 1980’s by Richard Swan of ARMS and adopted by the US Government in 1995. If the “ARMS” name looks familiar, you may remember the ARMS short rail adapter that screwed into the top of the fixed carry handle of the early M16/M15 models permitting the mounting of a scope or other optic on top of the handle. It carried a federal parts number, and it was a coveted accessory in the civilian world.

And look where we are now. We not only have a flattop M-1913 receiver, but Knight’s Armament Rail Adapter System (RAS) incorporated into the FN M4A1 and M16A2 models. The RAS provides Picatinny rails on all four sides of the forearm and when not in use, the rails are covered with Knight’s Armament quick detachable rail covers. The RAS forearm tends to be very hand-filling if you’re not using vertical forearm grip but offers the utmost in mounting flexibility.

The use of Knight’s Armament parts on an official military model also reveals the flexible attitude seen today in the various ordnance corps. It’s no longer a “Not Invented Here” world, but a world in which “If it’s better, let’s adopt it!” Refreshing, to say the least.

The FN15 M4 and M16 both sport button-broached, 4140, chrome-lined barrels with a 1:7-inch twist and an A2-type compensator, an A2-style front sight, a fully adjustable, back-up, rear sight calibrated for elevation from 200 to 600 meters with a battle sight zero of 350m, an ambidextrous selector switch, a forward assist lever, shell deflector, Rail Adapter System (RAS) forearm, bayonet lug, sling points and a trigger factory rated between 4.75 and 7.75 pounds. On my Lyman electronic scale, the M4 trigger averaged 6.6 pounds and the M16 trigger, 7.2 pounds. Both triggers were crisp and broke cleanly.


Leupold’s AR cantilever mount (above) positions the height and eye relief of normal
scopes perfectly. A DoD-required UID (below) label further authenticates these FN’s
as issue replicas. The Burris PEPR mount also mounts scopes such as this Steiner 1-4X
for proper eye relief on AR-style rifles and carbines.


For range work, I mounted the M4 with Leupold’s Mark 6 1-6x20mm variable scope with a range-finding and trajectory-compensating reticle. My Mark 6 is calibrated for the 7.62 cartridge, and I will be reviewing it in more detail in an upcoming article.

The FN M16 was mounted with a Steiner 1-4X 24mm Military model scope with a reticle featuring vertical hash marks. Both optics featured an illuminated reticle, and both optics were mounted in an advanced cantilever mount. The Leupold mount is described as their “Integrated Mounting System” and the Burris model goes by “Proper Eye Position Ready” (PEPR). To overcome the problem of mounting normal scopes on the M4 or M16 platforms, the cantilever design both raises the height of the scope and positions the scope 2 inches or more forward, establishing a proper eye relief and field-of-view. I can’t live without them.

When it comes to accuracy acceptance standards for the M4 and M16 platforms, you may be surprised to learn that for the M16 it’s 5 MOA and for the M4, 5.6 MOA. That’s what you call “Good enough for government work.” Anyway, both FN’s did a lot better than that out on the range.

The leading US military round today is the M855A1 enhanced performance round featuring a copper alloy core and an exposed 19-grain, steel penetrator tip. It is designed to be more dependable on soft and hard targets, has proved to be highly accurate and yields higher velocities and less muzzle flash in the M4 carbines. I don’t have any, so my ammo selection for the range consisted of 52-grain Black Hills Match Hollow Point, 55-grain CorBon FMJ, 62-grain Federal Green Tip FMJ and 77-grain Black Hills Open Tip Match.

Two things are immediately interesting to me about the data. First, the velocity differences between the M4’s 14.5-inch barrel (extended to 16 inches with a pinned and welded on compensator) and the 20-inch barrel of the M16. Second, you would predict both models with their 1:7 twist barrels would favor the heavier bullets. As they say, “It ain’t necessarily so!” This was particularly evident with the lighter bullets in the M4. You simply can’t precisely predict what ammunition a particular AR will favor. My equivalent of an M4 shoots Black Hills 77-grain OTM into 0.5 MOA.

Out of curiosity, I then proceeded to shoot a 15-round composite target with the M16 using 5 rounds each of the 52-, 62- and 77-grain loads. The composite group measured 2.9 inches—not bad for three very different bullet weights and velocities.

FN has really given us a treasure and true collectibles by fielding their FN15 M4 Collector Carbine and FN15 M16 Collector Rifle. They’re the real deal, and I can’t imagine an AR collection without one or more of these FN’s exacting, mil-spec replicas.

But wait! There’s one more FN replica to add to your collection—their semi-automatic version of the M249 SAW—the squad automatic weapon. What a hoot!


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