M45/M56 Smartgun

The M56 Smartgun used by Jenette Vasquez

The M45 and M56 Smartguns are a family of two closely-related machine guns and several subvariants of each, used by the United States Colonial Marines and a number of other countries.

Weapon Designation:Machine Gun, 7.5mm, Smart-Targeting, M45/M56
Type:M45: Medium Machine Gun
M56: Light Machine Gun
Place of Origin:Germany
In Service:2032-present
Production History:
Designed:2028-2031
Manufacturer:Rheinmetall
Produced:2031-present
Specifications:
Weight:M45: 16.3 lbs (7.39 kg)
M56: 14.4 lbs (6.53 kg)
Length:M45: 51.1 in (1,298 mm)
M56: 48.5 in (1,232 mm)
Barrel Length:M45: 21 in (533 mm)
M56: 20 in (508 mm)
Cartridge:M45: 7.5x50mm
M56: 10x24mm
Action:M45: Gas-operated, electronically ignited cartridges
M56: Straight blowback, electronically ignited cartridges
Rate of Fire:700 rounds/min cyclic
Muzzle Velocity:M45: 2,867 ft/s (873.86 m/s) with M7-5153 round
M56: 1,928 ft/s (587.65 m/s) with M10-210 round
Muzzle Energy:M45: 2,793 ft/lbs (3,787 Joules) with M7-5153 round
M56: 1,734 ft/lbs (2,350 Joules) with M10-210 round
Effective Range:M45: 1,300 m (1,422 yd)
M56: 300 m (328 yd)
Feed System:M45: 200-round belt (15.5 lbs)
M56: 300-round belt (13 lbs)
Sights:Heads-up display

Background:

In the late 2020s, the German Army, or Heer, requested a new machine gun design to replace the 7.62x51mm MG3, which was a derivative of the WWII-era MG42 machine gun. The desired weapon was to feature an integral targeting computer that could be linked with a heads-up display and a targeting network, allowing the operator to coordinate fire with other soldiers and even vehicles.

Although several companies submitted designs, it was made clear from the requirements for the weapon as well as the attitude of Heer command that Rheinmetall, producer of the MG3, would be given preference when it came time to choose the new weapon. However, in addition to their primary design being found superior to the competition regardless of the Heer’s preference, Rheinmetall’s win was also assured by the company’s offering of a secondary design which could complement the primary weapon in close-quarters use. The full-sized machine gun was adopted as the MG45 and the smaller version, which was designed using elements of the American M41 pulse rifle and was even chambered in the same 10x24mm caseless round, was adopted as the MG56. Both were accepted by the Heer in 2031, and the United States Marine Corps followed shortly after in 2032, accepting both designs as the M45 and M56, respectively. Their highly-advanced targeting computer systems quickly led to the nickname “smartgun” which at some point came into official use.

Design:

The M45 is the original version of the smartgun, and mechanically is closely related to the preceding MG3. There is, however, a significant number of differences between the MG3 and the M45. The most noticeable is the targeting computer and the prominent guard cage surrounding it, which attach to the barrel shroud at the halfway point. A large cylindrical flash hider has been added to the muzzle, while the standard pistol grip and mechanical trigger have been replaced with an electronic firing system activated from either of two points: a red button on the foregrip, or a lever on the rear grip. More subtle is the M45’s use of a short-stroke gas-powered piston operating system instead of the MG3’s recoil-operation design, which increases accuracy significantly, and the M56’s straight blowback system. The gas tube and piston on the M45 are hidden under the barrel shroud.

Although experiments were made with a harness that securely attached the weapon to the gunner, and even more radical experiments with a self-aiming mount attempted, the weight and training requirements were both significant points of concern, and the awkwardness of handling made it difficult for the operator to effectively take cover while carrying the weapon was shown in simulated combat tests to increase the chances of the operator being injured or killed by enemy fire. Other issues included the inability of the gun to be used in the prone position, requiring the gunner to assume a supine position lying on their back, which not only caused significant back fatigue, but also resulted in increased exposure to hostile fire and minimal ability to manage the weapon’s recoil.

Therefore, both versions of the smartgun are designed for use with a heavy-duty sling that mounts to the top rear of the receiver and the forward end of the top of the barrel shroud. This sling is intended to be looped over the operator’s left shoulder, and is adjustable for different-sized operators as well as different methods of holding the gun.

Points of Contact:

The M45 has five “points of contact”, or locations where the weapon can either be gripped, rested on, or mounted to. The first is a “chainsaw” grip mounted to the top of the barrel shroud just ahead of the receiver and protruding slightly to the left side of the weapon. The chainsaw grip also has a button which can fire the weapon. The button is protected by a small hinged shield which must be flipped up to the right in order for the gunner’s thumb to reach and press the button. This shield serves as both a passive safety and an active manual safety. The passive function is that it only opens a short way and is closed to the front and back of the weapon, meaning that the only way to reach the firing button is for the operator to deliberately reach their left thumb in from the foregrip. It cannot be accidentally pressed by the operator or a foreign object. The active manual safety function is that the weapon cannot be fired at all from either the button or the lever on the rear grip if the shield is in the closed position. When the shield is opened, it enables the electronic firing mechanism and also locks itself in position, so that it cannot be accidently knocked closed.

The second grip is a highly unconventional stock/rear grip combination which is often noted as resembling a motorcycle handlebar. This rear grip houses the recoil buffer assembly, and has a prominent lever underneath, which fires the weapon when lifted upward. These two grips are used for the primary method of carrying the weapon: at the right hip, with the right hand on the rear grip, and the left hand on the chainsaw grip, with the weapon’s weight additionally supported by its sling, looped over the operator’s left shoulder.

The third point of contact is the folding bipod mounted under the barrel shroud. This bipod is adjustable from three to six inches in height, and has a swivel mount so that the weapon can be aimed side-to-side without moving the bipod feet. Because of the slight increase in weight, it is not uncommon for operators to detach the bipod and carry it in a vest- or pants-mounted pouch, give it to their ammunition bearer to carry, or sometimes even leave it behind entirely.

One very-little known feature of the stock/rear grip assembly which is also highly unique is the method of shoulder-firing. The round end of the grip is entirely unsuitable for being braced against the operator’s shoulder, and yet there are situations in which shoulder-firing is desirable, such as in the prone or crouching positions in conjunction with the bipod. In order to accommodate this, the firing lever on the rear grip can be unlocked, pushed forward, and locked at a ninety-degree angle to the rear grip in a vertical position. The lever, which has a rubber pad on the upper/rear side, is then braced against the gunner’s shoulder, with the rear grip resting on top of the shoulder. This is exactly the opposite of a conventional stock design with a hinged buttplate: while an ordinary machine gun has a stock that can be braced against the shoulder, with a hinged plate that swings up and rests on top of the gunner’s shoulder to provide more stability, on the smartgun design, the hinged portion of the assembly, the firing lever, is braced against the shoulder and the stock rests on top of the shoulder.

This method of shoulder firing effectively eliminates one of the weapon’s two primary points of contact, the rear grip. Because it is resting on the shoulder, it cannot be used for aiming. Therefore, the weapon’s design incorporates a fourth point of contact: the non-reciprocating charging handle, which can be locked in the forward position. In order to operate the weapon in the prone or crouched position, or even firing the weapon from the shoulder while standing, the rear firing lever is locked in the vertical position (which also disables it from being able to fire the weapon until unlocked and returned to the horizontal position), the charging handle is locked forward, and the gunner grips the charging handle with their right hand and the chainsaw grip with their left, firing the weapon with the button on the chainsaw grip.

The fifth and final point of contact is a socket on the bottom of the receiver front, which allows the weapon to be attached to a tripod or vehicle pintle mount.

Ammunition, Feed System, Operating Mechanism, and Barrel:

The ammunition and operating mechanism are where the M45 and M56 smartguns differ. The M45 is chambered in 7.5x50mm, a cased, electronically-fired cartridge of similar size to the 7.62x51mm NATO round but with slightly increased performance, while the M56 is chambered in 10x24mm, the same round used by the M41 pulse rifle. This means that the M56 is slightly shorter and lighter than the M45, because the inner mechanisms and the receiver itself have been shortened to accommodate the shorter round. However, some of this weight is offset by the heavier barrel. While the M45 uses a 21-inch barrel and the M56 uses a 20-inch barrel, the M56’s barrel is slightly heavier because of its larger diameter.

Both variants of the smartgun are belt-fed. While the linked belts can be connected to form any length of belt desired, size and weight concerns mean that the M45 is issued with a polymer ammunition box slung under the weapon and loaded with 200 linked rounds of 7.5x50mm ammunition. This box weighs 13.8 lbs when full, bringing the weight of a fully-loaded M45 up from 16.3 lbs to a hefty 30.1 lbs. The M56, which uses lighter ammunition, is fed from a larger box holding 300 linked rounds, and weighs a total of 12.9 lbs, making the 14.4 lb M56 weigh 27.3 pounds when fully loaded. Alternatively, both versions can be equipped with a feed chute and ammunition backpack. The M45’s pack, which is given shape by a metal frame, is capable of holding 525 rounds, while the feed chute has room for another 75, giving the operator a maximum of 600 rounds at their disposal. The M56’s pack can only hold 440 rounds of the larger-diameter 10x24mm round (even with a slight increase in size), and an additional 60 rounds in the feed chute, giving the operator 500 rounds in a single reload.

Ordinarily, for both the M45 and the M56, the gunner will carry a standard ammunition box with its 300- or 200-round belt, while their ammunition bearer will carry an additional three to four boxes, depending on their strength and stamina levels, as well as the weapons they themselves are carrying. A unique feature for the M56 alone is the ability to use the M41 pulse rifle’s 40-round box magazines in an emergency, an idea inspired by the FN Minimi light machine gun.

The M45 is operated by a short-stroke, gas-powered piston, while the M56, which fires the lower-pressure 10x24mm round, uses a simpler straight-blowback system. This allows for further weight savings in the M56 by eliminating the operating rod and gas cylinder. Despite their different cartridges and operating systems, both the M45 and the M56 have been designed to permit a rate of fire of approximately 700 rounds per minute.

The difference in ammunition is also what determines the employment of the two weapons. The M45 is the more-commonly used of the two, and is used by the majority of Colonial Marine infantry gunners. The 7.5x50mm round gives the weapon similar performance to machine guns such as the FN MAG/M240, Kalashnikov PK, and MAS AA-52, and as such, it is utilized for most combat situations where these weapons would be used.

The M56, on the other hand, is reserved for close-quarters operations, mainly on ships and space stations, and in urban combat. As in the M41, the 10x24mm caseless ammunition is vulnerable to contamination, such as by water, which places some restrictions on the M56’s usage. It also has a much shorter effective range, but within that effective range, its explosive-tipped ammunition is capable of inflicting equal or greater damage on soft targets, and is slightly more capable of punching holes in body armor and barriers such as bulkheads than the 7.5x50mm round. In addition to the slightly superior terminal effects within 300 meters, the M56 is also slightly shorter and lighter as well as sharing ammunition with the M41 pulse rifle it is typically utilized alongside. This ammunition commonality also gives the M56 another advantage the M41 has: there is no need for concern about hot casings bouncing around and striking the operator or friendly soldiers.

Variants:

The smartgun family consists of the M45, the M56, and several subvariants of each.

M45B: The M45B was an attempt to return to a more conventional stock and pistol grip design like the MG3. Surprisingly, it turned out to be less-favored by users than the M45’s more unusual rear grip assembly and it was never widely used.

M45C: The M45C is a simplified M45 consisting of only the receiver, barrel, barrel shroud, and firing and feeding mechanisms. It is used in vehicle mounts, including coaxial mounts on the M34 Longstreet and M40 Ridgeway tanks, and on the UA 571-B sentry gun.

M45D: An M45 with rear spade grips and a backup reflex sight, intended for pintle mounts on aircraft and land vehicles.

M56B: Same as M45B. Adopted by the Heer, not accepted for use by the United States Marine Corps.

M56C: Same as M45C; intended for the smaller, lighter UA 571-C sentry gun.

M56D: Same as M45D.

Targeting Computer:

 The M336 targeting computer is the core of what sets the smartgun family apart from all other machine guns. Mounted on the top of the barrel shroud and protected by a prominent cage of bars surrounding it, the M336 works in conjunction with the M76 combat helmet to recognize, prioritize, and aid in targeting of hostile contacts. For the full technical report on the M76/M336 system, please refer to this document.

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