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FN HAMR (Heat Adaptive Modular Rifle) Introduced at AUSA 2010: FN SCAR Meets IAR (Infantry Automatic Rifle). FN MK16 SCAR-L goes open-bolt for sustained full-auto fire capability.

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

October 25, 2010
Updated/Modified on 10/25/10

This one just came in from FNH USA’s (FN Herstal USA) public relations (PR) firm. According to the press release DefenseReview (DR) received, FN Herstal just introduced the FN HAMR (Heat Adaptive Modular Rifle) a.k.a. FN HAMR-16 at AUSA 2010. The HAMR would appear to be FN’s take on the U.S. Marine Corpt (USMC) Infantry Automatic Rifle (IAR) concept, bridging the gap between a mag-fed (box magazine-fed) 5.56x45mm NATO (5.56mm NATO)/.223 Rem. assault rifle/carbine/SBR (Short Barreled Rifle) and a Light Machine Gun/Squad Automatic Weapon (LMG/SAW). Basically, the FN HAMR is the FN MK16 SCAR-L (SCAR-Light) meets IAR.

The HAMR fires from the closed-bolt position on both semi-auto and full auto, and automatically transitions into the open-bolt position during both fire modes (semi-auto and full-auto fire), once the chamber reaches a certain temperature (like during sustained fire situations), in order to prevent cook-offs. It then automatically transitions back to closed-bolt operation for both fire modes when the chamber temp drops back down to a safe level, making the FN HAMR an automatically thermo-regulated firearm/infantry small arm. That’s interesting.

Previous IARs just transition from closed-bolt semi-auto to open-bolt full-auto, once you hit the happy switch (safety/selector-switch) over to rock n’ roll (full-auto setting). While the primary purpose of switching to open-bolt operation for full-auto fire (and/or semi-auto fire, in this case) is to prevent cook-offs (rounds firing without pulling the trigger, due to excessive chamber heat) after extensive full-auto fire, open-bolt operation is required for certain types of weapon recoil attenuation/mitigatation, like the Ultimax 100 LMG’sConstant-Recoil” system and MPS AA-12 full-auto combat shotgun’s recoil mitigation system. In fact, Defense Review doesn’t know of any advantage offered by closed-bolt operation in the full-auto firing mode.

Complete weapon weight is 11.2 lbs. Defense Review is guessing that the HAMR’s additional weapon weight vs. the standard FN MK-16 SCAR-L is due to the addition of a heat sink and heavy barrel, not just a Grip Pod System, but we don’t yet have confirmation/verification on that. We also don’t yet know whether the Grip Pod is the GPS02 model or the heavier-duty “hard core” GPS01SAW model.

So, what do you, our readers, think about the FN Heat Adaptive Modular Rifle (HAMR)? We’re interested in your thoughts.

The following is the press release we received from FNH:

FN HAMR unveiled at AUSA

McLean, Va.(October 25, 2010) – In conjunction with the 2010 AUSA Annual Meetings and Exposition being held next week in Washington, DC, FN Herstal is pleased to introduce the new FN Heat Adaptive Modular Rifle (HAMR).

Derived from the innovative FN SCAR™ weapon system, the new FN HAMR is a revolutionary, lightweight, magazine-fed, 5.56x45mm infantry weapon that enhances the automatic rifleman’s maneuverability and displacement speed while still providing the ability to suppress or destroy both area targets and point targets in today’s fluid battle space. In addition, the visual profile and the firing signature of the FN HAMR are virtually identical to that of the standard infantry rifle, thus reducing the counter-fire threat from enemy forces.

The high-tech FN HAMR platform is a unique, highly adaptable, fully-modular selective fire weapon system that bridges the gap between an individual battle rifle and a squad automatic light machine gun in one compact package. For enhanced accuracy and greater first-round reliability, the magazine-fed FN HAMR initially fires from the closed bolt in either semi-automatic or full-automatic modes. For added safety during sustained fire situations, the FN HAMR automatically transitions into open-bolt operation in both semi-automatic and full-automatic modes before reaching the cook-off temperature of the chambered cartridge. Once the chamber temperature has dropped to a safe level, the FN HAMR automatically transitions back to closed-bolt mode. These transitions between closed-bolt and open-bolt modes are thermally regulated by the FN HAMR and occur without any manual intervention by the operator.

“We are extremely enthusiastic in presenting the revolutionary technology incorporated into the FN HAMR,” noted Mark Cherpes, Vice President of Military Operations for FNH USA. “The FN HAMR is truly a leap ahead in small arms technology that immediately provides the U.S. Military greater insight into our concepts for the development of a lightweight, multipurpose machine gun / automatic rifle using conventional ammunition. The FN HAMR will provide a springboard to further advancements in weapon designs and high capacity feeding concepts.”


Caliber: 5.56x45mm NATO
Operating Principle: Short-stroke gas piston; firing from closed or open bolt
Bolt: Rotating with multiple lugs
Mode of Fire: Semi-automatic, full automatic
Feed Device: 30-round steel (detachable box) magazine
Barrel Twist: 1 in 7” (right-hand twist)

Maximum Effective Range:
Individual/Point Targets: 500 meters
Area Target: 600 meters

Complete Weapon: 11.2 lbs
(Unloaded with Grip Pod™ and Iron Sights)

Stock Extended: 38.80”
Stock Collapsed: 36.34”
Stock Folded: 28.80”

FNH USA, LLC is the sales and marketing arm of FN Herstal, S.A., Belgium. Its corporate mission is to expand its global leadership position in defense, law enforcement and commercial markets by delivering superior products and the finest in training and logistical support. Visit to view the entire line of FNH USA, LLC products and services. FNH USA, LLC, P.O. Box 697, McLean, VA 22101 USA.”

Company Contact Info:

Tes Salb
FN Herstal USA (FNH USA)
Phone: 703-288-3500 Ext. 125
Email: [email protected]

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FN HAMR (Heat Adaptive Modular Rifle) Introduced at AUSA 2010: FN SCAR Meets IAR (Infantry Automatic Rifle). FN MK16 SCAR-L goes open-bolt for sustained full-auto fire capability. by

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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