The Army's M-4 Carbine: Background and Issues for Congress
The Army’s M-4 Carbine: Background and
Issues for Congress
Andrew Feickert
Specialist in Military Ground Forces
Foreign Affairs, Defense, and Trade Division
Summary
The M-4 carbine is the Army’s primary individual combat weapon for infantry
units. The M-4 uses a direct gas impingement system that blows carbon from the fired
cartridge back into the weapon’s receiver, which can lead to weapon malfunctions. The
U.S. Special Operations Command (USSOCOM) is replacing its M-4s with the Special
Operations Combat Assault Rifle (SCAR). It is a modular weapon with a short-stroke
piston system which eliminates carbon blow back that theoretically improves reliability.
Some have questioned why the Army has not adopted the SCAR or another similarly
designed weapon. A series of studies and tests of the M-4 and potential competitors
have added to this debate. This report will be updated as events warrant.
Background
In the mid-1990s, the Army began fielding the M-4 carbine, a lighter, more compact
version of the Vietnam-era M-16 rifle. Both M-16 and M-4 carbines are 5.56 mm caliber
weapons and are primarily manufactured by Colt Defense LLC, Hartford, CT. Army
officials are said to be satisfied with the M-16 family of weapons, suggesting that the M-
16 is “simply too expensive to replace with anything less than a significant leap in
technology.”1 The Army’s “leap ahead” program to replace the M-16 family of weapons
— the Objective Individual Combat Weapon (OICW) program — began in 1994, and one
weapon evaluated in that program, Heckler & Koch’s XM-8 assault rifle, was considered
by some as the M-16’s/M-4’s replacement. As late as 2005, the XM-8 was reportedly
close to being officially approved as the Army’s new assault rifle, but alleged acquisition
and bureaucratic conflicts compelled the Army to cancel the XM-8 in October 2005. The
Army plans to continue its procurement of M-16s and M-4s for “years to come,” while
1 Matthew Cox, “Better Than M4, But You Can’t Have One,” Army Times, March 1, 2007, and
“Competition Sought for New Army Rifle,” Army Times, April 27, 2007.
some in Congress have called for an “open competition” to choose a successor to the M-
Concerns with M-4 Reliability and Lethality
Reports suggest that soldiers have expressed concerns regarding the reliability and
lethality of the M-4.3 Reliability can be described as “the probability that an item can
perform its intended function for a specified interval under stated conditions” and lethality
as “the killing or stopping power of a bullet when fired from a weapon.”4
Center for Naval Analyses (CNA) Study on Small Arms in Combat.5 In
December 2006, the Center for Naval Analyses (CNA) published a survey and study at
the request of the Army’s Project Manager-Soldier Weapons of 2,600 soldiers who had
returned from Iraq and Afghanistan and who had engaged in a firefight using a variety of
small arms. Some of the M-4-specific observations were as follows:
!Over 50% of soldiers using the M-4 and M-16 reported that they never
experienced a stoppage [malfunction] while in theater, to include during
training firing of the weapons (p. 2).
!Frequency of disassembled cleaning had no effect on the occurrences of
stoppages. Variations in lubrication practices, such as the type of
lubrication used and the amount of lubrication applied, also had little
effect on stoppages. Using a dry lubricant decreased reports for
stoppages only for M-4 users (p. 3).
!Of soldiers surveyed who used the M-4, 89% reported being satisfied
with their weapon (p. 11).
!Of M-4 users, 20% recommended a larger bullet for the M-4 to increase
lethality (p. 30).
!Regarding M-16s and M-4s,many soldiers and experts in theater
commented on the limited ability to effectively stop targets, saying that
those personnel targets who were shot multiple times were still able to
continue fighting (p. 29).
Although M-4 critics cite this report as evidence of unsuitability of the M-4, it might
also be interpreted as a favorable report on the M-4’s overall reliability and acceptance
by soldiers. The “larger bullet” recommendation for lethality purposes may, in fact, be
a valid recommendation based on observations from Iraq and Afghanistan, but the “bigger
bullet debate” has been a source of contention for many small arms experts ever since the
Army adopted the 5.56 mm M-16 during Vietnam in lieu of the 7.62 mm M-14 rifle.
2 Ibid.
3 Ibid.
4 Shawn T. Jenkins and Douglas S. Lowrey, “A Comparative Small Analysis of Current and
Planned Small Arms Weapon Systems,” MBA Professional Report, Naval Postgraduate School,
Monterey, CA, December 2004, pp. 29-31.
5 Information in this section is taken from Center for Naval Analyses (CNA) Study: “Soldier
Perspectives on Small Arms in Combat,” December 2006. CNA is a federally-funded research
and development center (FFRDC) for the Department of the Navy.
Special Forces6 Opts to Replace the M-4
In 2001, the U.S. Special Operations Command (USSOCOM) was said to have
documented M-4 reliability problems in an official report, noting that the M-4 suffered
from an “obsolete operating system” and recommending the redesign of the current gas
system.7 The USSOCOM report allegedly described the M-4’s shortened barrel and gas
tube as a “fundamentally flawed”design, which contributed to failures extracting and
ejecting spent cartridges during firing. In recognition of these deficiencies, the 1st Special
Forces Operational Detachment-Delta, also referred to as “Delta Force,”reportedly began
working with German arms manufacturer Heckler & Koch to replace the M-4’s gas
system with a piston operating system to improve reliability and increase parts life. In
2004, Delta reportedly replaced their M-4s with the HK-416 — a weapon that combines
the operating characteristics of the M-4 with the piston operating system.8
In early 2003, USSOCOM officials initiated efforts to identify potential new combat
rifle capabilities.9 From May through August 2004, USSOCOM evaluated 12 weapons
from nine different manufacturers.10 In November 2004, USSOCOM awarded a contract
to FNH USA11 to develop the Special Operations Combat Assault Rifle (SCAR).12 The
SCAR will come in two variants — the heavy 7.62 mm SCAR-H and the light 5.56 mm
SCAR-L. 13 Each variant will accommodate three different barrels — a standard 35.7 cm
barrel, a 25.5 cm close-combat barrel, and a sniper variant barrel. All barrels reportedly
will take less than five minutes to switch. The SCAR-L is intended to replace
USSOCOM M4-A1 carbines and features the same type of gas piston operating system
that the HK 416 employs. The SCAR is currently undergoing the final phases of initial
operational test and evaluation, with a full-rate production decision projected for 2008,
and with initial delivery quantities of around 2,800 weapons to be allocated throughout
USSOCOM units.14
6 For additional information on U.S. Special Forces, see CRS Report RS21048, U.S. Special
Operations Forces (SOF): Background and Issues for Congress.
7 Information in this section is from Matthew Cox, “Better Than M4, But You Can’t have One,”
Army Times, March 1, 2007.
8 Matthew Cox and Kris Osborn, “M4,In Their Sights,” Defense News, February 25, 2008.
9 Scott R. Gourley, “Soldier Armed: Special Operations Forces Combat Assault Rifles,”
Association of the U.S. Army (AUSA) Army Magazine, May 1, 2006.
10 “US SOCOM Awards Contract for SCAR Development,” Jane’s International Defense
Review, January 2008, p. 26.
11 FNH USA is the U.S.-based sales and marketing entity for the Belgium-based FN Herstal S.A.
12 Scott R. Gourley, “SCAR Evaluation Nears Conclusion,” Jane’s Defence Weekly, March 19,
13 Information in this section is from Joshua Kucera, “SOCOM Selects New Assault Rifle,”
Jane’s Defence Weekly, February 5, 2005, p. 8.
14 Scott R. Gourley, “SCAR Evaluation Nears Conclusion,” Jane’s Defence Weekly, March 19,
Army’s Asymmetric Warfare Group and the H&K-416
The Army describes the recently established Asymmetric Warfare Group (AWG),
based in Ft. Meade, MD, as an Army special missions unit consisting of carefully selected
military, Department of the Army Civilians, and contractors who “observe and collect
information about the evolving asymmetric operating environment by providing advisors
to deployed and deploying forces in support in the Global War on Terrorism.”15 The
Army reportedly initially approved AWG acquisition and use of HK-416s in lieu of M-4s,
but then reversed this decision stating, “The AWG also advises units on training, tactics,
and procedures. In this capacity, the use of the standard issue M-4 is required. In support
of this mission set, the decision was made to transition to the M-4 and the AWG is now
turning in its H&K rifles.”16 A report maintains that AWG “fought to keep its several
hundred 416s, arguing that they outperform the Army’s M-4 and require far less
maintenance.” Because the HK-416 operates in a similar fashion to the M-4 and has
comparable performance characteristics, it is unlikely that training, tactics, and procedures
vary greatly between the two weapons, thereby causing some to question the motives
behind the Army’s decision to recall the AWG’s HK-416s.
M-4 Reliability Testing
A 2002 Marine Corps Systems Command test was said to have concluded that the
M-4 malfunctioned three times more often that the M-16A4, as the M-4 failed 186 times
for a variety of reasons over the course of 69,000 rounds fired, while the M-16A4 failed17
61 times. In a test conducted by the Army between October 2005 and April 2006, 10
new M-16s and 10 new M-4s were fired in a 35,000-round test under laboratory
conditions, with both weapons firing approximately 5,000 rounds between stoppages.
Congressionally Requested M-4 Test. In April 2007, Senator Tom Coburn
(R-Oklahoma) sent a letter to then Acting Secretary of the Army Peter Geren questioning
why the Army planned to spend $375 million on M-4 carbines through FY2009 “without
considering newer and possibly better weapons available on the commercial market.”18
Senator Coburn’s letter also cited M-4 reliability and lethality concerns and called for a
competition to evaluate alternatives to the M-4, citing a need to conduct a “free and open
competition.” The Army initially agreed to begin the tests in August 2007 at the Army
Test and Evaluation Center at Aberdeen Proving Ground, MD, but then postponed the test
until December 2007.19 The test evaluated the M-4 against the HK-416, the HK -XM8,
and the FNH SCAR, with each weapon firing 6,000 rounds under sandstorm conditions.
15 See 2008 U.S. Army Posture Statement Information Paper — Asymmetric Warfare Group
[http://www.army.mil/aps/08/information_papers/prepare/Army_Asymmetric_Warfare_
Group.html], accessed May 20, 2009.
16 Information in this section is from Matthew Cox, “Army Takes HK416s From Special Unit,”
Army Times, March 11, 2008.
17 Matthew Cox, “Better Than M4, But You Can’t Have One,” Army Times, March 1, 2007.
18 Information in this section is from Matthew Cox, “Competition Sought for New Army Rifle,”
Army Times, April 27, 2007.
19 Matthew Cox, “Army Tests of Rival Carbines Postponed,” Army Times, September 20, 2007.
Officials reportedly evaluated 10 each of the four weapons, firing a total of 60,000 rounds
per model resulting in the following: XM-8, 127 stoppages; FNH SCAR, 226 stoppages;
HK-416, 233 stoppages; and the M-4, 882 stoppages.20 On December 17, 2007, when the
Army briefed Congress and the press, the Army reportedly claimed that the M-4 suffered
only 296 stoppages during the test, explaining that the stoppage discrepancy from the
original 882 M-4 stoppages reported could have been due to the application of the Army
Test and Evaluation Center’s post-test Reliability, Availability, and Maintainability
(RAM) Scoring Conference.21 This process attributes failures to such factors as operator
error or part failure and, as an example, if evaluators linked 10 stoppages to a broken part
on a weapon, they could eliminate nine of the stoppages and count only one failure for
reporting purposes. It is not known whether the Army also applied the RAM process to
the other three weapons in the test, but it might be assumed that if the other three weapons
were given equal treatment, those weapon’s stoppages would also likely be decreased in
a manner similar to the M-4.
Recent Congressional Action
The Administration requested $151.1 million in FY2009 for the procurement of
88,964 M-4 carbines to be produced by Colt of Hartford, CT, at $1,200 per weapon (not
including combat optics and other accessories).22 There is also a request for an additional
$79.5 million for 47,185 M-4s in the pending FY2008 Global War on Terror
Supplemental Request that has not yet been acted on in Congress.23
The House and Senate have approved the Administration’s FY2009 M-4 Budget
Request (see H.R. 5658 and S. 3001, FY2009 National Defense Authorization Act).
Accompanying H.Rept. 110-652, May 16, 2008, calls for the services to work together
to develop and resource a joint, long-term competitive strategy for small arms, including
a “next-generation carbine.” S.Rept. 11-335, May 12, 2008, recommends “that Secretary
of Defense submit a report on the feasibility and advisability of conducting a full and open
competition for carbine-type weapons.” (Sec.112, S.Rept. 11-335.)
Potential Issues for Congress
Additional Reliability and Lethality Testing. Although many feel that recent
tests, studies, and surveys call into question the Army’s decision to continue to procure
and employ the M-4 carbine, it can also be argued that the M-4 is generally well-regarded
by the soldiers who use it in combat and its lethality may be more a function of the round
used as opposed to the actual weapon itself. One potential option for gaining greater
insight into this issue might be to outfit selected Army infantry companies (about 120
soldiers) in both Iraq and Afghanistan with XM-8s, HK-416s, and FNH SCARs for a
year-long comparative study with an infantry company equipped with M-4s. Such a
20 Matthew Cox, “New Carbines Outperform M-4 in Dust Test,” Army Times, December 17,
21 Information in this section is from Matthew Cox, “Giving M-4 Failures an Alibi,” Army Times,
December 29, 2007.
22 DOD Budget Item Justification Sheet, M-4 Carbine, February 2008, pp. 197-200.
23 Department of the Army, FY2008 GWoT Exhibit P-1G, February 2008, p. A-9.
study, conducted in combat as opposed to in laboratories and on firing ranges, might
provide what could be described as “the ultimate test” of these weapons. Such testing is
not unprecedented, as the Army has recently tested its Land Warrior integrated modular
combat system in Iraq with an infantry battalion in actual combat.
USSOCOM Implications of Replacing M-4s. It can be argued that
USSOCOM’s decision to adopt the FNH SCAR has implications for the Army. In one
sense, the SCAR is the first modular small arms system adopted by the military. The
SCAR-L and SCAR-H will replace the following weapons: M-4A1, MK-18 close quarter
carbine, MK-11 sniper security rifle, MK-12 special purpose rifle, and the M-14 rifle.24
There is also a 90% parts commonality between the SCAR-L and SCAR-H, including a
common upper receiver and stock and trigger housing and an enhanced grenade launcher25
can be attached to either model. While the SCAR might not meet all of the conventional
Army’s requirements, its adaptability in terms of missions (close quarters combat to long-
range sniper operations), being able to rapidly convert from a 5.56 mm to a 7.62 mm
weapon, and the ability to accommodate a variety of modifications such as grenade
launchers and special optics, might be factors worth considering as the “modular
Army”plans future small arms programs.
Open Competition for an M-4 Replacement. Some small arms analysts have
detected “a growing frustration among arms makers that the Army is wedded to a single
company.”26 Congress has also asked the Army and DOD to study and report on the
feasibility and advisability of conducting an open competition for carbine-type weapons
and to develop a long-term, competitive strategy for small arms. If such an effort is
undertaken by the Army and the other Services, some might argue that lessons learned
from past Army small arms initiatives such as the Objective Individual Combat Weapon
(OICW) program and, more recently, USSOCOM’s Special Operations Combat Assault
Rifle (SCAR) program, would facilitate such a competition and procurement. The SCAR
program involved a 10-month “full and open competition” resulting in nine
manufacturers submitting 12 weapons for consideration.27 The program was described
as “operator-envisioned, operator-tested, and operator chosen,”with Navy, Army, and
Marine special operators being extensively involved in design and testing.28 Supporters
of a competition maintain that a number of existing carbine manufacturers are available
and that a precedent for joint development and testing is already established. From their
perspective, a new Army initiative would benefit both in terms of reduced procurement
time and developmental costs.
24 Scott R. Gourley, “Soldier Armed: Special Operations Forces Combat Assault Rifles,”
Association of the U.S. Army (AUSA) Army Magazine, May 1, 2006.
25 Nathan Hodge, “Stopping Power,” Jane’s Defence Weekly, July 25, 2007.
26 Matthew Cox and Kris Osborn, “M4,In Their Sights,” Defense News, February 25, 2008.
27 Scott R. Gourley, “Soldier Armed: Special Operations Forces Combat Assault Rifles,”
Association of the U.S. Army (AUSA) Army Magazine, May 1, 2006 and “US SOCOM Awards
Contract for SCAR Development,” Jane’s International Defense Review, January 2008, p. 26.
28 Ibid.