M4 carbine
The
M4 carbine is a family of firearms tracing its lineage back to earlier
carbine versions of the
M16, all based on the original
AR-15 designed by
Eugene Stoner and made by
ArmaLite. It is a shorter and lighter version of the
M16A2 assault rifle, with 80% parts commonality.
[2]
The
M4 has
selective fire options including
semi-automatic and
three-round burst (like the M16A2), while the
M4A1 has a "
full auto" option instead of three-round burst. The possible successor to the M4 carbine in the U.S. Army is the
Individual Carbine.
[3]
Overview
The M4 and its variants fire
5.56x45mm NATO ammunition (or
.223 Remington ammunition) and are
gas-operated, air-cooled,
magazine-fed, selective fire
firearms with a multi-position
telescoping stock.
[4] Original M4 models had a flat-ended telescoping
stock, but newer models are now equipped with a redesigned telescoping stock that is slightly larger with curvature at the end.
[5] The M4 is similar to much earlier compact M16 versions, such as the 1960s-era
XM177 family. Some of those visual designs are obvious in both weapons, however most of the similarities are not very noticeable.
The M4 with the newer, redesigned telescoping
stock As with many
carbines, the M4 is handy and more convenient to carry than a full-length
rifle. The price is slightly inferior ballistic performance compared to the full-size M16, with its nearly 6" (15 cm) longer barrel. This becomes most apparent at ranges of 300 yards and beyond. Statistically, however, most small-arms engagements occur within 100 yards.
[citation needed] This means that the M4 is very much an adequate weapon for the majority of troops. The marginal sacrifice in
terminal ballistics and range, in exchange for greatly improved handling characteristics, is usually thought to be a worthwhile compromise.
While the M4's maneuverability makes it a candidate for non-
infantry troops (vehicle crews, clerks and staff officers), it also makes it ideal for
close quarters battle (CQB). The M4 was developed and produced for the
United States government by
Colt Firearms, which had an exclusive contract to produce the M4 family of weapons through 2009;
[citation needed] however, a number of other manufacturers offer M4-like firearms. The M4A1, along with the
M16A4, have mostly replaced the M16A2 in the Army and Marines. The
U.S. Air Force, for example, plans to transition completely to the M4 for security squadrons. They maintain a yearly qualification with the carbine.
The
United States Marine Corps has ordered its officers (up to the rank of lieutenant colonel) and Staff Non-commissioned officers to carry the M4A1 carbine instead of the
M9 handgun. This is in keeping with the Marine Corps motto, "Every Marine is a rifleman."
United States Navy corpsmen will also be issued M4A1s instead of the M9.
[6]
[edit] History and variants
Except for the very first delivery order, all U.S. military-issue M4 and M4A1 possess a flat-top
NATO M1913-specification (Picatinny) rail on top of the
receiver for attachment of optical sights and other aiming devices —
Trijicon TA01 and TA31
Advanced Combat Optical Gunsights (ACOG),
EOTech 550 series holographic sights, and
Aimpoint M68 Close Combat Optic (M68 CCO) being the favorite choices — and a detachable rail-mounted carrying handle. Standards are the Colt Model
920 (M4) and
921 (M4A1).
Variants of the carbine built by different manufacturers are also in service with many other foreign special forces units, such as the
Australian Special Air Service Regiment (SASR). While the SASR uses weapons of essentially the same pattern built by Colt for export (Colt uses different models to separate weapons for the U.S. military and those for commercial/export purposes), the British
SAS uses a variant on the basic theme, the
Colt Canada (formerly
Diemaco)
C8SFW.
[edit] M4 MWS (Modular Weapon System)
M4 MWS (Modular Weapon System) shown with various accessories including
M203 grenade launcher, RIS foregrip, removable carry handle/rear sight assembly,
AN/PEQ-4 laser system,
M68 CCO reflex sight, and the
AN/PVS-4 night vision optics
Colt Model
925 carbines were tested fitted with the
Knight's Armament Corporation (KAC) M4 RAS under the designation
M4E2, but this designation appears to have been scrapped in favor of mounting this system to existing carbines without changing the designation. The U.S. Army Field Manual specifies for the Army that adding the Rail Adapter System (RAS) turns the weapon into the
M4 MWS or
Modular Weapon System.
The
M4A1 carbine is a fully-automatic variant of the basic M4 carbine intended for
special operations use. The M4A1 has a "S-1-F" (safe/semi-automatic/fully automatic) trigger group, while the M4 has a "S-1-3" (safe/semi-automatic/3-round burst) trigger group. The M4A1 is used by almost all U.S special operation units. The M4A1 is especially favored by
counter-terrorist and
special forces units for close quarters combat because of the carbine's compactness and firepower. These features are also very useful in
urban warfare. Although the M4 has less effective range than the longer M16, many military analysts consider engagement with a non-specialized small arm above a range of 300 meters (330
yd) to be unnecessary. It is effective at ranges of 150 meters (160 yd) or less and has a maximum effective range of about 500 to 600 meters (550–660 yd).
[7]
In the last few years, M4A1 carbines have been refit or received straight from factory with barrels with a thicker profile under the handguard. This is for a variety of reasons such as heat dissipation, which is useful due to the complaints of high-heat production from test soldiers, which occurs during full-auto and accuracy as a byproduct of barrel weight. These heavier barrel weapons are also fitted with a heavier buffer known as the H2. Out of three sliding weights inside the buffer, the H2 possesses two tungsten weights and one steel weight, versus the standard H buffer, which uses one tungsten weight and two steel weights. These weapons, known by Colt as the Model 921HB (for
Heavy Barrel), have also been designated M4A1, and as far as the government is concerned the M4A1 represents both the
921 and
921HB.
[edit] SOPMOD Block I
SOPMOD (Special Operations Peculiar Modification) Block I
USSOCOM developed the Special Operations Peculiar Modification (
SOPMOD) Block I kit for the carbines used by units under its jurisdiction. The kit features an M4A1, a Rail Interface System (RIS) handguard developed by Knight's Armament Company, a shortened quick-detachable
M203 grenade launcher and
leaf sight, a KAC
sound suppressor, a KAC back-up rear sight, an Insight Technologies
AN/PEQ-2A visible
laser/
infrared designator, along with Trijicon's ACOG and
Reflex sights, and a
night vision sight. This kit was designed to be configurable (modular) for various missions, and the kit is currently in service with special operations units.
[edit] SOPMOD Block II
A second-generation SOPMOD kit (now known as
SOPMOD II) is currently under development, with many different manufacturers competing for the contract. Notable bidders include Knight's Armament Company, Atlantic Research Marketing Systems (ARMS), and Lewis Machine & Tools. Daniel Defense has won the contract for the RIS-II, the next generation of rail handguards.
[edit] Improved M4
On July 1, 2009, the U.S. Army took complete ownership of the M4 design.
[8] This will allow companies besides Colt to compete with their own M4 designs. The Army is planning on fielding the last of its M4 requirement in 2010.
[8] On October 30, 2009, Army weapons officials proposed a series of changes to the M4 to Congress. Requested changes include an electronic round counter that records the number of shots fired, a heavier barrel, and replacing the
direct impingement system with a
gas piston system.
[9] As of September of 2010 the Army has announced they will buy 12,000 M4A1s from Colt Firearms by the end of 2010 and will by early 2011 order 25,000 more M4A1s. The Army announced also to have open competition for newly designed M4 bolt carrier and gas piston operation system, which will be fitted to the newly bought M4A1 carbines. the army plans to buy 12,000 of these conversion kits in early 2011. In late 2011 the Army plans to buy 65,000 more conversion kits. From there the Army will decide if it will upgrade all of its M4s.
[10]
[edit] Future replacement
The carbine variant of the
XM8 rifle was canceled in 2005.
On November 13, 2008, the U.S. Army hosted an invitation-only Industry Day regarding a potential future replacement for the M4 carbine. Nineteen companies provided displays and briefings for military officials. The weapons displayed included the
Barrett REC7 PDW,
Bushmaster ACR,
FN SCAR,
Heckler & Koch HK416,
Heckler & Koch XM8,
LWRC M6A4,
Robinson Arms XCR,
SIG 556, as well as Colt's own improved version of the M4, the
Colt ACC-M (Advanced Colt Carbine-Monolithic). The goal of the Industry Day was to provide officials with knowledge as to the current state of the art, which will assist the writing of a formal requirements document.
[11]
The possible successor to the M4 carbine in the U.S. Army is the
Individual Carbine.
[3] This program is to provide a new carbine for the Army, while the USMC has decided to stay with the M4 for carbine use.
[10]
[edit] Design
The M4/M4A1 5.56mm carbine is a gas-operated, air-cooled, magazine-fed, selective fire, shoulder-fired weapon with a telescoping stock. A shortened variant of the M16A2 rifle with a 14.5
in (368
mm) barrel, the M4 provides the individual soldier operating in close quarters the capability to engage targets at extended range with accurate, lethal fire. The original M4 has
semi-automatic and three-round burst fire modes, while the M4A1 has "semi" and "full auto", with no three-round burst. The M4 has over 80% commonality with the M16A2 rifle and was intended to replace the
.45 ACP M3 submachine guns and selected M9 pistols and M16 rifle series with most Army units (this plan was thought to be changed with the development of the
XM29 OICW and the
XM8 carbine; however, both projects were canceled.) The M4 is also capable of mounting an
M203 grenade launcher, the M203A1 with a 9-inch barrel as opposed to the standard 12-inch barrel of the M203 used on the M16 series of rifle.
Some features of the M4 and M4A1 compared to a full-length M16-series rifle include:
- Compact size
- Shortened barrel 14.5 in (368 mm)
- Telescoping buttstock
However, there have been some criticisms of the carbine, such as lower
muzzle velocities and louder report due to the shorter barrel, additional stress on parts because of the shorter gas system, and a tendency to overheat faster than the M16A2.
[edit] Accessories
An M4A1 just after firing, with an ejected
case in mid-air; the
M203 and
M68 CCO are attached.
Like all the variants of the M16, the M4 and the M4A1 can be fitted with many accessories, such as night vision devices, suppressors, laser pointers, telescopic sights,
bipods, either the
M203 or
M320 grenade launchers, the
M26 MASS shotgun, and anything else compatible with a MIL-STD-1913 Picatinny rail.
Other common accessories include the
AN/PEQ-2,
Advanced Combat Optical Gunsight (ACOG), and
M68 CCO.
EOTech holographic weapon sights are part of the SOPMOD II package. Visible and IR (infrared) lights of various manufacturers are also commonly attached using various mounting methods. As with all versions of the M16, the M4 accepts a
blank-firing attachment (BFA) for training purposes.
[edit] Effectiveness
An April 2002 presentation by the
US Army Natick Soldier Center presented by LTC Charlie Dean and SFC Sam Newland reported on lessons learned from M4 use in
Afghanistan (such as use during
Operation Anaconda):
[citation needed]
- 90% of soldiers reported confidence in the weapon.
- 20% were dissatisfied with its need of maintenance.
- 34% of soldiers reported that their M4's handguards rattled and became excessively hot when firing.
- 15% reported that they had trouble zeroing the M68 reflex sight.
- 35% added barber brushes and 24% added dental picks to their cleaning kits.
- Soldiers reported the following malfunctions:
- 20% reported double-feeding.
- 15% reported feeding jams.
- 13% reported that feeding problems were usually due to magazines.
Soldiers requested the following changes:
- 55% requested the firearm be made lighter.
- 20% requested a slightly larger magazine.
[edit] 2007 dust test
In the fall 2007, the Army tested the M4 against three other carbines in "
sandstorm conditions" at
Aberdeen Proving Ground,
Maryland: the
Heckler & Koch XM8 rifle,
Fabrique Nationale de Herstal SOF Combat Assault Rifle (SCAR) and the
Heckler & Koch HK416. Ten of each type of rifle were used to fire 6,000 rounds each, for a total of 60,000 rounds per rifle type.
[12] The M4 suffered far more stoppages than its competitors: 882 stoppages, 19 requiring an armorer to fix. The XM8 had the fewest stoppages, 116 minor stoppages and 11 major ones, followed by the
FN SCAR with 226 stoppages and the HK416 with 233.
[13][14] The Army was quick to point out that even with 863 minor stoppages—termed "class one" stoppages which require 10 seconds or less to clear and "class two" stoppages which require more than ten seconds to clear—the M4 functioned well, with over 98 percent of the 60,000 total rounds firing without a problem. The Army said it planned to improve the M4 with a new cold-hammer-forged barrel to give longer life and more reliable magazines to reduce the stoppages. Magazine failures caused 239 of the M4's 882 failures. Army officials said the new magazines could be combat-ready by spring if testing went well.
[15]
[edit] Gas Piston
Complicating the Army search for higher effectiveness in the M4 is a number of observations of M4 gas piston alternatives that suffer unintended design problems. The first is that many of the gas piston modifications for the M4 isolate the piston so that piston jams require the entire weapon be disassembled. The second is that gas piston alternatives use an off-axis operation of the piston that can introduce carrier tilt, whereby the bolt carrier fails to enter the buffer tube at a straight angle resulting in part wearing. The third is that the use of a sound suppressor results in hot gases entering the chamber, regardless of a direct-gas impingement or gas piston design choice.
[16]
[edit] Trademark issues
A U.S. Marshal covers a doorway with an M4.
Colt previously held a U.S.
trademark on the term "M4".
[17] Many manufacturers have production firearms that are essentially identical to a military M4. Civilian models are sometimes colloquially referred to as "M4gery"
[18] (pronounced
/ɛmˈfɔərdʒəri/,
us dict:
ĕm·fōr′·jər·ē, a
portmanteau of "M4" and "forgery"). Colt had maintained that it retains sole rights to the M4 name and design. Other manufacturers had long maintained that Colt had been overstating its rights, and that "M4" had now become a generic term for a shortened AR-15. In April 2004, Colt filed a lawsuit against
Heckler & Koch and
Bushmaster Firearms, claiming acts of
trademark infringement,
trade dress infringement,
trademark dilution, false designation of origin,
false advertising,
patent infringement,
unfair competition, and deceptive trade practices. Heckler & Koch later settled out of court, changing one product's name from "HK M4" to
"HK416". However, on December 8, 2005, a District court judge in
Maine granted a
summary judgment in favor of Bushmaster Firearms, dismissing all of Colt's claims except for false advertising. On the latter claim, Colt could not recover monetary damages. The court also ruled that "M4" was now a generic name, and that Colt's trademark should be revoked.
[19]
Italy
United States Military
