Are the FN SCAR Weapons (MK16 and MK17) Necessary? And do we really need to replace the Colt M4/M4A1 Carbine?

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By David Crane
defrev (at) gmail (dot) com

May 20, 2009

According to Army Times magazine, The 75th Ranger Regiment is scheduled to battle test the Special Operations Combat Assault Rifle (SCAR) very soon. The Rangers will reportedly be taking 600 FN SCAR rifle/carbine/subcarbine/SBR (Short-Barreled Rifle) weapons packages into battle, but DefenseReview doesn’t know how many of these are the 5.56×45mm NATO (5.56mm NATO) FN MK16 (formerly SCAR-Light a.k.a. SCAR-L) assault rifle/carbine/subcarbine/SBR variant, and how many are the 7.62×51mm NATO (7.62mm NATO) FN MK17 (formerly SCAR-Heavy a.k.a. SCAR-H) battle rifle/carbine/subcarbine/SBR variant.

The SCAR weapons are select-fire and operate via a short-stroke gas piston/op-rod (operating rod) (SSGP/OR) mechanism vs. the Colt M4A1 Carbine’s direct-gas-impingement (DGI) a.k.a. direct-impingement gas (DI gas) operating mechanism and were designed and developed to replace the Colt MK18 CQBR (Close Quarters Battle Receiver) 5.56mm SBR, Knight’s Armament (KAC) MK11/SR-25 7.62mm semi-auto sniper rifle, 5.56mm MK12 SPR (Special Purpose Rifle) (5.56mm), and the M14 7.62mm battle rifle. The SCAR weapons are modular, and military operators can choose barrel lengths of approx. 10″, 14″, and 18″ for the MK 16 and approx. 13″, 16″, and 20″ for the MK 17. The MK16 takes a 30-round magazine, and the MK17 takes a 20-round mag. The SCAR weapons offer a reported 80% parts commonality between the two variants.

Defense Review recently spoke to one of our professional contacts in the tactical firearms community, and he told us on the phone that the MK16/SCAR-L is for all practical purposes “dead”, meaning that it’s not likely to survive for very long, and that the SCAR weapons are continuing to experience teething problems in the field, i.e. breaking down. We don’t have confirmation/verification on this yet, so it’s just a rumor at this point. Anything’s possible, but we’ve spoken with people in the U.S. military Special Operations community who prefer either the AR-config HK416 (also written HK 416) for a gas piston/op-rod carbine/SBR solution or a good old-fashioned DGI Colt SOPMOD M4A1 Carbine or MK18 CQBR SBR for a DGI solution.

On the subject of piston-driven vs. direct-gas-driven weapons, while gas piston-driven weapons have been all the rage over the last few years, there’s a growing list of tactical AR cognoscenti, aficionados, and builders that are pushing back againt the march to gas piston/op-rod Nervana, making the case that piston-driven systems may not necessarily be a better mousetrap after all, and in a number of ways, are actually inferior to the combat-proven DGI operating system.

Direct-gas-impingement operation offers significant accuracy and weight advantages over gas piston/op-rod operation in AR (AR-15)-config weapons. For example, Heckler & Koch (HK) had to significantly thicken the barrel on the HK416 (also written HK-416) to counteract barrel flex caused by the forces exerted by the offset, reciprocating gas piston and operating rod. This barrel flex resulted in accuracy problems and vertical stringing of shots during full-auto fire. Understand that a gas piston/op-rod setup is already inherently heavier than a direct-gas-impingement setup, and thickening the barrel made the HK 416 heavier than it initially was.

It should perhaps be noted that a primary reason for the movement towards short-stroke gas piston/op-rod operation (and the use of the HK416 SBR, specifically) instead of direct-gas-impingement operation by elements in U.S. Army Special Forces and U.S. military Special Operations Forces (SOF) out of USSOCOM a.k.a. SOCOM was due to their desire to suppress 10.5-inch (10.5″)-barreled SBRs. Attaching a silencer/sound suppressor a.k.a. “muzzle can” to carbine or SBR changes the pressure and fouling dynamics of the weapon, and can cause reliability problems unless the weapon is specifically set up for suppressed use.

Even without a can attached, at 10.5″ inches, a DGI-operated AR15-config weapon like the Colt MK18 (formerly known as the Colt M4A1 CQBR)–which actually utilizes a 10.3″ barrel–is a bit too close to to the precipice of not working reliably, since the direct-gas operating system relies on a certain amount of barrel length to creat the correct amount of gas pressure for the correct amount of time, as well as a consistent level of gas pressure over time, to cycle the action (i.e. the bolt carrier group) and feed the next round. This “timing” element is crucial in a DGI AR-15 SBR for combat reliability. A suppressor just adds to the inherent and somewhat precarious pressure curve/timing issues of an AR-15 SBR.

However, if you add a high-tech self-lubricitous / self-lubricating, anti-rust/corrosion internal coating and a Precision Reflex (PRI) M84 Gas Buster Charging Handle – Military Big Latch, to a direct-gas AR, it may be possible to at least address the fouling issue. With this type of coating, DGI weapons may be able to handle the suppressed role (silencer/sound suppressor a.k.a. “muzzle can” attached to the weapon) just as effectively as a piston gun (unconfirmed/unverified). DefenseReview would have to test this, theory, however, and we may do this soon. The PRI M84 Gas Buster Charging Handle attenuates/mitigates hot gas and particulate matter backblast into the shooters face, which has been a criticism of suppressed DGI AR carbines and SBRs, including the M4A1 Carbine.

High-tech firearm coating technologies such as the Next Generation Arms (NGA) internal ceramic coating, the FailZero “AR-15 Basic Kit” and “AR-15 Extreme Duty Kit” nickel-boron (Ni-B)-coated AR-15 parts and components, and the Robar NP3 PTFE (polytetrafluoroethylene) a.k.a. Teflon)/electroless nickel coating/finish may reduce/mitigate internal “crud” a.k.a. fouling build-up inside a suppressed DGI AR-15 carbine SBR enough to allow it to work reliably at a high-enough round count to negate the gas piston/op-rod system’s advantages in this specific area. We’ll see.

It’s noteworthy that tactical instructor, author, and DefenseReview contributor Mike Pannone, a retired U.S. Army Special Forces (SF) operator, prefers a 12.5-inch (12.5″) barrel for a direct-gas-impingement AR-15 SBR. Since a 12.5″ AR SBR can utilize a standard carbine-length gas system (DGI), Pannone believes that 12.5 inches is the optimum barrel length for a DGI AR SBR, since it provides for optimum weapon utility. Basically, a 12.5″ AR-15 SBR offers the perfect balance of weapon compactness and versatility, reliability (provided by adequate barrel length to achieve the right pressure curve and timing), and muzzle velocity for adequate terminal ballistics/lethality. The one caveat is that the weapon has to be set up right, or “sprung right”.

In order to ensure this, Pannone developed the BHI Enhanced M4 SOPMOD Bolt Upgrade Kit being sold by Blackheart International (BHI), which, according to him, will solve the majority of M4/M4A1 Carbine and semi-auto-only AR-15 carbine reliability problems, all by itself. The kit includes a mil-spec extractor with a 5-coil extra-power extractor spring, Crane O-ring to elimate extractor bounce, 3 mil-spec gas rings, a mil-spec Black Buffer (H2 buffer), which also reduces exractor bounce, a Sprinco Extreme Duty Buffer Spring/Main Spring, which lasts 4-5 times longer than a standard buffer spring and “adds additional tension to absorb recoil; energy, and ensure reliable feeding, chambering and locking”, and a DPMS Rate Reducing Buffer. BHI says the following about the DPMS Rate-Reducing Buffer: “This buffer, along with the upgraded buffer spring will absorb more energy as the bolt cycles to the rear, slowing the bolt velocity and giving the shooter a much more manageable recoil impulse, and a decreased rate of fire on full-auto carbines. The heavier buffer will also ensure that feeding chambering, and locking on even a dry dirty chamber is positive and reliable.”

Provided the M4A1 Carbine (or semi-auto-only AR-15 carbine) is properly maintained by the end user and “sprung correctly”, i.e. outfitted with a BHI Enhanced M4 SOPMOD Bolt Upgrade Kit, Pannone argues that you’d be hard pressed to find anything better (i.e. more reliable), or even as good as the combat tested-and-proven Colt M4A1 Carbine.

It should perhaps also be noted that high-end tactical AR (tactical AR-15 weapons platform) builders John Noveske of Noveske Rifleworks, LLC and Nathan Roads of Next Generation Arms (NGA) both prefer direct-gas-impingement AR-15s to gas piston/op-rod ARs. DefenseReview found out about Noveske’s preference for DGI ARs during one of our interview sessions with him. Noveske and Roads also like the 12.5″ barrel length for DGI AR-15 SBRs.

So, does SOCOM really need the FN SCAR MK16 and MK17 weapons? Probably not. The fact is, while the SCAR family might potentially provide modularity and production cost advantages over the long term if SCAR is eventually adopted and it replaced all the weapons listed above that it’s intended to replace, it doesn’t offer any lethality advantages whatsoever over any of the already-fielded, combat tested and proven weapons it was designed and developed to replace.

The SCAR weapons simply aren’t revolutionary in any way with regard to combat capability and effectiveness. If anything, they’re more of an interim-level/bridging-the-gap solution until somone develops a truly revolutionary replacement for our currently-fielded weapons. Fact is, the MK-16/SCAR-L is a much more expensive proposition in the short term than just properly maintaining the legacy M4/M4A1 Carbines that are already in the system. Fact is, many SOCOM operators already prefer the HK416 (5.56mm) and HK417 (7.62mm) carbines and SBRs over SCAR for a short-stroke gas piston/op-rod weapon solution, if they’re going to replace the combat-proven M4A1 with anything. Fact is, the financial health of the U.S. military procurement system isn’t what it once was, due in large part to the financial realities of the country in general. And, fact is, there’s a new sheriff in town (Obama), and Demcocrat administrations aren’t traditionally conducive to a high level of military funding and support, at least not in the modern era.

And, again, rumor has it that SCAR weapons are breaking in the field (unconfirmed/unverified). Oh, and speaking of breaking, The HK-416 has apparently been experiencing its own share of parts breakages and reliability issues in the field, as well. Defense Review will further investigate the specific problems we’ve heard about for SCAR and the HK 416 as soon as we can.

Bottom line is that as time goes on, SCAR is looking more and more like an unnecessary indulgence and a waste of increasingly-scarce taxpayer dollars.

Editor’s Note: Mike Pannone (a.k.a. Michael Pannone) is the author of the M16/M4 Handbook and HK416 Handbook (also written HK-416 Handbook), which are invaluable resources to anyone who owns and/or uses an M4/M4A1 Carbine, tactical AR-15 carbine, or HK416 respectively. They’re also worthy additions to any tactical firearms library, even if you don’t own or use any of those weapons.

Company Contact Info:

FN Herstal USA (FNH USA) Military Operations
PO Box 896
McLean, VA 22101
Phone: 703-288-3500
Fax: 703-288-4505
E-Mail: [email protected]

FNH USA Military Training Operations
Phone: 1-540-752-6200
Fax: 1-540-752-0967

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About David Crane

David Crane started publishing online in 2001. Since that time, governments, military organizations, Special Operators (i.e. professional trigger pullers), agencies, and civilian tactical shooters the world over have come to depend on Defense Review as the authoritative source of news and information on "the latest and greatest" in the field of military defense and tactical technology and hardware, including tactical firearms, ammunition, equipment, gear, and training.

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