At the beginning of this century, the command of the United States Marine Corps was concerned with increasing the mobility of fighters and units by rearming them. Until now, the Marines used the M249 SAW as a light machine gun - a variant of the Belgian FN Minimi, modified to meet American requirements and produced in the States under license. "Saw" and was supposed to be replaced with a new, more convenient weapon. In general, KPM was the first to think of solving the problem of firepower and mobility of units in this way: they ordered a kind of hybrid of a light machine gun and an assault rifle. Although sometimes there is an opinion that the Marines simply wanted to get new infantry weapons without special economic and political problems - so they decided to replace the old M249, and not the new M4 rifles. The competition for the development of a replacement for the Saw was called very "original": IAR (Infantry Automatic Rifle - Infantry Automatic Rifle).
FN, Heckler-Koch and Colt submitted their bids for the competition. In the first company, or rather in its American department (FN USA), they decided to take the FN SCAR rifle already in the hardware as a basis. After a series of modifications designed to adapt the automatic mechanism to the peculiarities of the machine gun, the FN IAR project "spun off" from the FN SCAR. Apparently, the firm also decided not to philosophize about the name. Later, the weapon will be renamed, and it will be called FN HAMR (Heat Adaptive Modular Rifle - Modular rifle with heat adaptation). Probably, now the rifle was supposed to attract a potential customer already at the name stage. Moreover, representatives of FN have not tired of repeating for many years that this very system of thermal adaptation is a revolutionary innovation, which in the future will become the standard for all weapons, and everyone will remember their company with a kind word.
What is the adaptation system? By default, FN HAMR fires from a closed bolt. This achieves firing performance that is acceptable for an assault rifle. In this case, you can shoot both in bursts and in single shots. If the unit needs a machine gun, the FN HAMR fighter will use his weapon in the appropriate way. Moreover, the ammunition supply of the rifle in the "machine-gun" mode can be carried out both from a standard box magazine for 30 rounds, and from other designs that are compatible with the corresponding STANAG standard. So, for example, for the FN HAMR in the role of a machine gun, it is most expedient to use Beta C-Mag magazines (two-drum for a hundred rounds). However, in this case, the rifle, which has become a machine gun, will experience completely different temperature loads, which can have an extremely bad effect on the firing performance. For this case, FN USA came up with an interesting mechanism that regulates the operation of automation depending on the temperature of the rifle's insides. Naturally, FN do not share their know-how, but the most probable and logical way of thermoregulation work is as follows: a bimetallic plate contacts the rifle chamber, which, when a certain temperature is exceeded, through the linkage system, "commands" the sear to lock the bolt in the rear position. Shooting is now conducted, respectively, from an open bolt. Due to this, air circulation in the receiver is improved, and the temperature of the structure is gradually reduced. When the recommended one is reached, the mechanism releases the bolt and then the FN HAMR fires “automatic”, from the closed bolt. The designers note that all these switchings occur completely automatically, without human intervention. So the shooter no longer needs to keep track of the number of cartridges fired and replace the barrel in time.
With the exception of the temperature adaptation mechanism and the barrel, the FN HAMR is similar to the base SCAR rifle in the light version. This weapon was created for the 5, 56x45 mm NATO cartridge. HAMR automatic equipment is gas-operated with a short piston stroke. The barrel is locked by means of a rotary cylinder, on seven lugs. From the ancestor rifle, the HAMR retained a two-block receiver layout. In the upper part, made of aluminum, the barrel and the shutter mechanics are fixed, and in the lower polymer - the firing mechanism, pistol grip and magazine receiver. The barrel of a temperature-adaptive rifle, like the SCAR, is removable, but has a greater wall thickness - again, in order to withstand increased temperature loads. The FN HAMR trigger mechanism allows you to fire with single shots and bursts, the designers did not provide for adjusting the length of the latter. The three-position fire translator flag (blocking trigger, single, automatic), as on a large number of modern types of weapons, is located on both sides above the pistol grip, which allows you to switch it with both hands. Also, for the convenience of left-handed shooters, it is possible to quickly and easily rearrange the loading handle to the left side (initially located on the right). To do this, there are slots on both sides of the receiver, and holes for the handle on the bolt. In addition, the magazine latch has buttons on both sides. So that the left-handed shooter does not get a face injury from a flying out sleeve, there is a reflector part in the back of the ejection window.
At the factory, the FN HAMR rifle is equipped with folding sights, consisting of a diopter rear sight and an open front sight. The first one is adjustable for firing range. The stock, like the SCAR, is foldable (to the right) and can be adjusted in length. The modularity from the name on the HAMR is provided by three Picatinny rails: at the top of the receiver, under the forend and on the left side. In addition to the "tactical body kit", they can be mounted on the FN EGLM underbarrel grenade launcher, designed specifically for the SCAR line. According to unconfirmed reports, in the factory configuration, the FN HAMR has an additional front grip that folds into a bipod for use in machine gun mode.
In 2009, based on the results of comparative tests, the US Marine Corps competition committee recommended the Heckler-Koch M27 assault rifle for service. In a number of sources there is information that by 2014 the ILC will receive 6-7 thousand copies of Heckler-Koch. At the same time, one cannot exclude the possibility that the Marines will decide to buy Belgian-American rifles in addition, because the IAR competition was, first of all, an experiment to change the structure of units. If the experiment is recognized as successful, then the purchase of the FN HAMR is quite possible, especially since by that time this rifle will have time to finally be brought to mind.
