Colonial Marine Corps M16A5P

The M16A5P is the standard-issue rifle of the United States Armed Forces, as well as most other countries of the Nations United Interplanetary Military Force. An updated form of the famous M16 rifle, the M16A5P is most notable for using an electronic firing system rather than the M16’s traditional hammer firing mechanism. The electronic “pulse” system is considered far more reliable than a traditional mechanical ignition group, as it contains no moving parts aside from the trigger and requires essentially no maintenance, as well as being more accurate because it has a precisely consistent trigger pull and no perceptible delay between the trigger being pulled and the cartridge being fired.

The M16A5P is chambered in a new high-velocity round that is more accurate and has significantly better terminal effects than the 5.56x45mm NATO round used by older M16 models.

The rifle was found to be so effective that it continued in service for over 150 years, although this was also partly due to the Future Weapons Development Ban passed in 2036. In addition, three variants, the M656P marksman rifle, the M950P heavy-barrel assault rifle, and the M933P carbine have also been developed from the M16A5P and serve alongside it.

Weapon Designation:Rifle, 5.6mm, Pulse-Fired, M16A5P
Type:Assault Rifle
Place of Origin:United States
Production History:
Manufacturer:Colt Arms Manufacturing
Weight:6.5 lb (2.95 kg)
Length:39.5 in (1,003 mm) (fixed stock/collapsible stock open)
35.5 in (901 mm) (collapsible stock closed)
Barrel Length:20 in (508 mm)
Action:Gas-operated direct impingement, electronically ignited cartridges
Rate of Fire:700 rounds/min cyclic
Muzzle Velocity:3,407 ft/s (1,038 m/s) with M5-662 round
Muzzle Energy:1,598 ft/lbs (2,167 Joules)(with M5-662 round
Effective Range:800 m (765 yd)
Feed System:30-round detachable box magazine
Sights:Iron sights or Colt 3.5x scope


In 2026, Jonathan LaForce, a retired United States Marine Corps Colonel, began work on an experimental submachine gun he called the XM41. The Marine Corps eventually became aware of the project, and was so interested that they not only encouraged him to continue developing it, but even borrowed concepts from the weapon for a full-sized service rifle utilizing caseless, electronically-fired ammunition, which was developed by Armat Battlefield Systems alongside LaForce’s private endeavor. However, the XM37 proved to have only mediocre reliability and the fragility and susceptibility to contamination of the caseless ammunition led to the rifle being considered unacceptable for the harsh environments in which it would be used, and the US military refused to adopt it. However, they still wanted an electronically-fired rifle, and because they planned to accept the M41 if it passed the trials, an opportunity was presented to introduce a new rifle design.

In the place of the XM37, it was decided to bring back the older M16 design in an attempt to improve it with the new electronic firing mechanism. The result was a combination of several features from the M16’s history, as well as some new features. It was officially adopted in 2030, and a large number of nations followed suit. With the passage of the Weapons Development Ban, part of the Cooperative Exploration Treaty, in 2036, weapons technology development became drastically limited, to the point that it was virtually impossible to design a more technologically-advanced firearm, and so the M16A5P continued on in its role for over 150 years.


The M16A5P’s upper and lower receivers are manufactured from titanium aluminide alloy, giving unprecedented strength and lightness for a weapon of its size. It was the first mass-produced full-sized rifle constructed from titanium aluminide. It can be used with either a fixed or collapsible stock. The fixed stock is more popular because it can be used to hold the rifle’s cleaning kit, while the cleaning kit must be carried separately if a collapsible stock is used instead. The M16A5P uses the older but simpler round handguard design of the M16A2 rather than the M16A4’s rail system, which was essentially rendered obsolete by new helmet designs that allow Marines to move their weapon-mounted accessories to their helmets instead. Any accessories that need to be attached to the weapon itself can be mounted by use of a special rail that is screwed to the upper or lower handguard through the vent holes. As the three-round burst mode of the M16A2 and M16A4 was found unsatisfactory, the electronic firing mechanism of the M16A5P is programmed for safe, single shot, and fully automatic fire, selected by a traditional rotating switch. It retains the bolt catch to lock the bolt back after the magazine is emptied, but additionally has an auto-close feature that automatically closes the bolt and chambers a round when a fresh magazine is inserted. The upper receiver also lacks a forward assist, which was felt to be unnecessary and provide minimal functionality. In place of the forward assist is a small LED display that shows the remaining ammunition in the weapon’s magazine in red numbers. The display can be dimmed for night operations or even shut off entirely. Unlike the display on the M41, the M16A5P’s display is pointed backwards towards the operator so that it can be more easily viewed by right-handed users, and the display screen and numbers are much smaller. The battery that powers this screen and the electronic firing system is in the rifle’s pistol grip, and can easily be changed by sliding the bottom cover backwards off the grip, pulling out the battery, inserting a new one, and replacing the cover.


The 20-inch barrel is constructed of a proprietary steel-carbon-stellite alloy, making it exceptionally wear-resistant. The barrel profile measures 0.675 inches in diameter behind the front sight post and 0.75 inches from the front sight post forward. It has 1:9 right-hand six-groove rifling to adequately stabilize the 62-grain steel-core M5-662 round used by the rifle.


The M16A5P dispenses with the flattop receiver and detachable carrying handle of the M16A4, instead featuring the fixed carrying handle of the M16A2 and the associated iron sights. However, it’s not uncommon for the M16A5P to be used with a 3.5x magnification scope mounted on the carrying handle. The scope is almost identical in appearance and function to the 3x20mm Colt scope designed for the first M16s, but greatly modernized, with a basic mil-dot reticle.

Range, Accuracy, and Terminal Ballistics:

The M16A5P is widely regarded as an exceptionally accurate rifle, with its standard issue ammunition, the M5-662 round obtaining a 95% hit rate on an 8×8-target at 600 meters. When combined with the 3.5x scope, the M16A5P is officially listed as being accurate out to 800 meters.

Terminal effects for the 5.6x47mm round are greatly improved over the 5.56x45mm NATO round. The 62-grain bullet used by the cartridge is a fluted design machined from copper with a steel core insert. The fluted design gives the bullet devastating effects in soft tissue while the steel core makes it capable of penetrating many types of body armor. The M16A5P and the M5-662 round are considered to be terminally effective out to the limit of their accurate range, 800 meters.

Additional Accessories

The M16A5P is meant for use with the M31 bayonet, which serves as a multi-purpose bayonet, fighting knife, and utility tool. It can also mount the M320A4 under-barrel grenade launcher and the U7 underbarrel shotgun.

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