Editing M16 rifle (section)

==Reliability==
[[File:DIRECTM16.gif|thumb|The M16 gas redirect system, incorrectly labeled as direct impingement. The gif does not show the operating mechanism of the rifle, only the gas redirect system.]]
During the early part of its service, the M16 had a reputation for poor reliability and a malfunction rate of two per 1000 rounds fired.{{sfnp|''HCAS Hearings''|1969|p=2326}} The M16's action works by passing high-pressure propellant gasses, tapped from the barrel, down a tube and into the carrier group within the upper receiver. The gas goes from the gas tube, through the bolt carrier key, and into the inside of the carrier where it expands in a donut-shaped gas-piston cylinder. Because the bolt is prevented from moving forward by the barrel, the carrier is driven to the rear by the expanding gases and thus converts the energy of the gas to the movement of the rifle's parts. The back part of the bolt forms a piston head and the cavity in the bolt carrier is the piston sleeve. While the M16 is commonly said to use a [[direct impingement]] system, this is wrong, and it is instead correct to say it uses an ''internal piston'' system.{{sfnp|''Armalite''|2010}}  This system is however ammunition specific, since it does not have an adjustable gas port or valve to adjust the weapon to various propellant and projectile or barrel length specific pressure behavior.

The M16 operating system designed by [[Eugene Stoner|Stoner]] is lighter and more compact than a gas-piston design. However, this design requires that combustion byproducts from the discharged cartridge be blown into the receiver as well. This accumulating carbon and vaporized metal build-up within the receiver and bolt carrier negatively affects reliability and necessitates more intensive maintenance on the part of the individual soldier. The channeling of gasses into the bolt carrier during operation increases the amount of heat that is deposited in the receiver while firing the M16 and causes the essential lubricant to be "burned off". This requires frequent and generous applications of appropriate lubricant.{{sfnp|Ehrhart|2009|p=39}} Lack of proper lubrication is the most common source of weapon stoppages or jams<!--in general, or in M16's?-->.{{sfnp|Ehrhart|2009|p=39-41}}

The original M16 fared poorly in the jungles of Vietnam and was infamous for reliability problems in harsh environments. [[Max Hastings]] was very critical of the M16's general field issue in Vietnam just as grievous design flaws were becoming apparent. He further states that the ''Shooting Times'' experienced repeated malfunctions with a test M16 and assumed these would be corrected before military use, but they were not. Many marines and soldiers were so angry with the reliability problems they began writing home and on 26 March 1967, the ''Washington Daily News'' broke the story.{{sfnp|Hastings|2018|p=350-354}} Eventually, the M16 became the target of a congressional investigation.{{NoteTag|This was dubbed the Ichord hearings after Missouri representative Richard Ichord, who championed Congress's inquiry into failures of the M-16 during the Vietnam War.{{sfnp|Kahaner|2007|p=236}} }}

The investigation found that:{{sfnp|Defense Technical Information Center (DTIC)|1968|p=5}}
* The M16 was issued to troops without cleaning kits or instructions on how to clean the rifle.
* The M16 and 5.56×45mm cartridge was tested and approved with the use of a DuPont IMR8208M [[Improved military rifle powder|extruded powder]], which was switched to Olin Mathieson WC846 [[ball powder]] which produced much more fouling, which quickly jammed the action of the M16 (unless the gun was cleaned well and often).
* The M16 lacked a [[forward assist]] (rendering the rifle inoperable when it failed to go fully forward).
* The M16 lacked a chrome-plated chamber, which allowed corrosion problems and contributed to case-extraction failures (which was considered the most severe problem and required extreme measures to clear, such as inserting the cleaning rod down the barrel and knocking the spent cartridge out).

[[File:Front cover - the M16A1 Rifle - Operation and Preventive Maintenance (art by Will Eisner).jpg|thumb|right|Front cover – ''The M16A1 Rifle – Operation and Preventive Maintenance'' by [[Will Eisner]], issued to American soldiers in the [[Vietnam War]].]]
When these issues were addressed and corrected by the M16A1, the reliability problems decreased greatly.{{sfnp|Ezell|Pegg|Smith|Smith|1993|pp=46-47}} According to a 1968 Department of Army report, the M16A1 rifle achieved widespread acceptance by U.S. troops in Vietnam.{{sfnp|Coomer|1968|p=10}} "Most men armed with the M16 in Vietnam rated this rifle's performance high, however, many men entertained some misgivings about the M16's reliability. When asked what weapon they preferred to carry in combat, 85 percent indicated that they wanted either the M16 or its [smaller] carbine-length version, the [[CAR-15|XM177E2]]." Also, "the M14 was preferred by 15 percent, while less than one percent wished to carry either the [[Stoner 63|Stoner rifle]], the AK-47, the [M1] carbine or a pistol."{{sfnp|Coomer|1968|p=25}} In March 1970, the "President's Blue Ribbon Defense Panel" concluded that the issuance of the M16 saved the lives of 20,000 U.S. servicemen during the Vietnam War, who would have otherwise died had the M14 remained in service.{{sfnp|Hallock|1970|p=18-33}} However, the M16 rifle's reputation has suffered as of 2011.{{sfnmp|1a1=Ezell|1a2=Pegg|1a3=Smith|1a4=Smith|1y=1993|1pp=46-47|2a1=Rottman|2y=2011|2p=30}}

Another underlying cause of the M16's jamming problem was identified by ordnance staff that discovered that Stoner and ammunition manufacturers had initially tested the AR-15 using DuPont IMR8208M extruded (stick) powder. Later ammunition manufacturers adopted the more readily available Olin Mathieson WC846 ball powder. The ball powder produced a longer peak chamber pressure with undesired timing effects. Upon firing, the cartridge case expands and seals the chamber ([[obturation]]). When the peak pressure starts to drop the cartridge case contracts and then can be extracted. With ball powder, the cartridge case was not contracted enough during extraction due to the longer peak pressure period. The ejector would then fail to extract the cartridge case, tearing through the case rim, and leaving an obturated case behind.{{sfnp|''Fenix Ammunition, History of the .223...''|2021}}

After the introduction of the M4 carbine, it was found that the shorter barrel length of 14.5 inches also harms the reliability, as the gas port is located closer to the chamber than the gas port of the standard length M16 rifle: 7.5&nbsp;inches instead of 13&nbsp;inches.{{sfnp|''Armalite''|2003}} This affects the M4's timing and increases the amount of stress and heat on the critical components, thereby reducing reliability.{{sfnp|''Armalite''|2003}} In a 2002 assessment, the USMC found that the M4 malfunctioned three times more often than the M16A4 (the M4 failed 186 times for 69,000 rounds fired, while the M16A4 failed 61 times).{{sfnp|''Defense Industry Daily''|2011}} Thereafter, the Army and Colt worked to make modifications to the M4s and M16A4s to address the problems found.{{sfnp|''Defense Industry Daily''|2011}} In tests conducted in 2005 and 2006 the Army found that on average, the new M4s and M16s fired approximately 5,000 rounds between stoppages.{{sfnp|''Defense Industry Daily''|2011}}{{sfnp|Jenkins|Lowrey|2004|p=25}}

In December 2006, the [[Center for Naval Analyses]] (CNA) released a report on U.S. small arms in combat. The CNA conducted surveys on 2,608 troops returning from combat in Iraq and Afghanistan over the past 12 months. Only troops who had fired their weapons at enemy targets were allowed to participate. 1,188 troops were armed with M16A2 or A4 rifles, making up 46 percent of the survey. 75 percent of M16 users (891 troops) reported they were satisfied with the weapon. 60 percent (713 troops) were satisfied with handling qualities such as handguards, size, and weight. Of the 40 percent dissatisfied, most were with its size. Only 19 percent of M16 users (226 troops) reported a stoppage, while 80 percent of those that experienced a stoppage said it had little impact on their ability to clear the stoppage and re-engage their target. Half of the M16 users experienced failures in their magazines to feed. 83 percent (986 troops) did not need their rifles repaired while in the theater. 71 percent (843 troops) were confident in the M16's reliability, defined as a level of soldier confidence their weapon will fire without malfunction, and 72 percent (855 troops) were confident in its durability, defined as a level of soldier confidence their weapon will not break or need repair. Both factors were attributed to high levels of soldiers performing their maintenance. 60 percent of M16 users offered recommendations for improvements. Requests included greater bullet lethality, newly built instead of rebuilt rifles, better-quality magazines, decreased weight, and a collapsible stock. Some users recommended shorter and lighter weapons such as the [[M4 carbine]].{{sfnp|Russell|2006|p=25}} Some issues have been addressed with the issuing of the [[STANAG magazine#Issues and improvements|Improved STANAG magazine]] in March 2009,{{sfnp|''The Firearm Blog'', 13 June 2009}}{{sfnp|''The Firearm Blog'', 16 December 2009}} and the [[5.56×45mm NATO#M855A1|M855A1 Enhanced Performance Round]] in June 2010.{{sfnp|''Picatinny Arsenal'', 24 June 2010}}

In early 2010, two journalists from ''[[The New York Times]]'' spent three months with soldiers and Marines in Afghanistan. While there, they questioned around 100 infantry troops about the reliability of their M16 rifles, as well as the M4 carbine. The troops did not report reliability problems with their rifles. While only 100 troops were asked, they engaged in daily fighting in [[Marjah, Afghanistan|Marja]], including at least a dozen intense engagements in [[Helmand Province]], where the ground is covered in fine powdered sand (called "moon dust" by troops) that can stick to firearms.{{sfnp|''The New York Times, At War Blog'', July 7, 2010}} Weapons were often dusty, wet, and covered in mud. Intense firefights lasted hours with several magazines being expended. Only one soldier reported a jam when his M16 was covered in mud after climbing out of a canal. The weapon was cleared and resumed firing with the next chambered round. Furthermore, the Marine Chief Warrant Officer responsible for weapons training and performance of the Third Battalion, Sixth Marines, reported that "We've had nil in the way of problems; we've had no issues", with his [[battalion]]'s 350 M16s and 700 M4s.{{sfnp|''The New York Times, At War Blog'', July 7, 2010}}