M14 Rifle History And Development

PrefaceThis work is an honest and reasonable attempt at capturing the history and developmentof the M14 rifle. The reader is encouraged to check the facts for himself. The M14 riflestory is still very much in progress.Thank you to members of the www.eotacforum.com, www.m-14forum.com, andwww.warrifles.com Internet discussion boards for their support and helpful suggestions.Special thanks go to LAW483 Enterprises, Sadlak Industries, Smith Enterprise,SparrowHawk Stocks, Troy Industries, Warbirds Custom Guns, and William J. RiccaSurplus for their generous assistance. The author thanks those who have contributed tothis work but wish to remain anonymous. Other Sources # 12, # 18 and # 27 madesignificant contributions to this volume.The copy editing chore for the First Edition was freely and graciously donated by Brent A.Blanchard, Attorney and Counselor at Law. Mr. Blanchard learned to shoot from his dadas a child. He shot smallbore rifle as a teenager and was a member of the BrighamYoung University Army ROTC Rifle Team. He competed in High Power competitionmatches in the 1980s while the M14 rifle was king of competition shooting. After helearned that careers in public relations, marketing, and financial planning were not to hisliking, Mr. Blanchard went to law school. He was admitted to the bar in the State ofNevada after graduation and later accepted a position at a law firm in Las Vegas, NV.William Cook Richards generously gave his time to the task of copy editing for theSecond Edition. Additionally, his thoughtful suggestions regarding the use of publishingsoftware resulted in a better layout with the Second Edition.There are no double quotes before and after specific alphanumeric characters used toidentify equipment and rifle parts. The substantial number of rifle part identifying marksand dimensional measurements included in the narrow focus of this volume rendersthose conventions distracting. In this work, “Springfield Armory” refers to the U. S.government installation. The name “Springfield Armory, Inc.” belongs to the commercialfirearms manufacturer.Due to the nature of the Internet, web site addresses listed in the Bibliography wereactive at the time research was conducted but may not work thereafter. Some riflemodels, parts or accessories discussed in this work may not be available due to thelimited number made or because the manufacturer is no longer in business.Always handle all firearms in a safe manner. There are four basic rules of firearmssafety: 1) Treat every gun as if it was loaded 2) Never point the muzzle at anythingyou are not willing to destroy 3) Keep your finger off the trigger until the sights areon the target and 4) Always be sure of your target and what is behind and to thesides of it. Metal targets present a ricochet hazard. Ricochets can come back to thefiring line from which they originated. Wear proper attire, e.g., no tank tops, and personalprotective equipment (ear muffs or plugs and shooting glasses) when shooting.

LEE EMERSONAlways read and follow product safety warnings and instructions. This includes allfirearms, ammunition, accessories, and gun care products. Use hand and portable toolssafely and in the manner for which they are designed. Consult with law enforcementofficials or an attorney if you are unsure of the law where you live.I trust you will find this work helpful in your pursuit of happiness.Lee EmersonAugust 2010Las Vegas, NV10

Part 1The Military M14IntroductionThe U.S. Rifle 7.62 mm M14 was adopted for military service by the United States on May01, 1957. The announcement was made by William H. Brucker, Secretary of the Army.The rifle was officially designated M14 in the U. S. Army Ordnance Technical Committeedocument OTCM 36558 on June 05, 1957. The M14 rifle was developed to replace fourtypes of military small arms: M1 Rifle, M1 and M2 Carbines, M1918 Browning AutomaticRifle and M3A1 submachine gun. This was an ambitious goal reflecting the long-standingtraditions of economy and marksmanship in the U. S. Army. The technology of the timewas unable to overcome the laws of nature. The result was a rifle with a heavy hittingcartridge that was tough to manage in automatic fire and too heavy and too long in theminds of its critics and some of its operators. Regardless, the M14 has performedsuperbly in its primary role, battle rifle.The M in M14 stands for Model. The M14 rifle is a rotating bolt, gas operated, air cooled,magazine fed, shoulder fired weapon. The M14 is 44.28 " long with the hinged butt platein the closed position and weighs 8.8 pounds. With a full magazine, cleaning kit andsling, it weighs approximately 11.2 pounds. The maximum effective range is 460 meters(503 yards). The M14 has seen hostile service with the American military from the 1963Cuban missile crisis to the Global War on Terrorism. The M14 rifle has been employedas a battle rifle, squad automatic weapon, competition match rifle, grenade launcher,sniper weapon system and ceremonial rifle.Between 1958 and 1963, the U. S. government ordered 1,380,358 M14 rifles from fourentities. These were the U. S. Army’s Springfield Armory in Springfield, MA; Winchester(Olin Mathieson Chemical Corporation) in New Haven, CT; Harrington & RichardsonArms Company in Worcester, MA; and Thompson-Ramo-Wooldridge, Inc. in Cleveland,OH. A total of 1,376,031 M14 rifles were delivered between 1959 and 1964. InDecember 1962, just before Secretary of Defense Robert McNamara announcedcancellation of the project, the U. S. Army had planned a procurement schedule totaling2,500,000 M14 rifles by June 30, 1969.From 1945 to June 30, 1957, the U. S. government spent 10,927,523 to research,develop, test and evaluate the M14. Total cumulative investment cost for the M14 projectwas 207,017,000. The total cumulative operating, maintenance and ammunition costsup to July 01, 1968 was 295,290,000. The average production cost was 105.15 perrifle with TRW being the most affordable of the four manufacturers. During rifleproduction, five magazines were packed with each rifle. The cost of the five magazineswas 4.20. The production learning curve slope was 92 percent. This means as

LEE EMERSONproduction quantities doubled, the time to produce each rifle decreased by 8 percent.The production cost per rifle continued to increase for each of the three commercialmanufacturers until each had produced 100,000 rifles. After that point, production costper rifle decreased as more rifles were completed. In 1968, the annual operating (parts,maintenance, and ammunition) cost for each rifle was 50.52. The cost of the M14project production equipment was as follows: Olin Mathieson Chemical Corporation 7,593,460, Harrington & Richardson - 6,330,726 and TRW - 6,824,559. The cost ofthe production equipment at Springfield Armory was not available when researched for a1968 U. S. Army Materiel Command report.In October 1968, the U. S. Army Materiel Command reported the following reliabilityfigures for the M14 rifle in Technical Report 68-4 M14 Rifle Cost Analysis Report:Mean Time To Overhaul (average time to overhaul a M14 rifle) - 1.5 hoursTime Between Overhaul (TBO) - 5 yearsMean Time Between Failure (MTBF or average time between any failure requiring repair)- 270 daysMean Time To Repair (MTTR) - 0.6 hoursAverage annual ammunition usage as of November 1965 - 810 cartridges (610 roundsball, 50 rounds tracer and 150 rounds blank).Engineering MaterialThere are three important factors which influence the quality of the M14 type rifle receiverand parts. These factors are material selection, heat treatment, and dimensionalgeometry. Selection of an engineering material is based upon the design, application andmanufacturing feasibility of an object. With that in mind, if the proper material is not used,the specified (and desired) values for each mechanical property (hardness, strength,toughness, etc.) may not be achieved for a given part, regardless of whether heattreatment is performed well or done at all. If the incorrect material is used to make thepart, the part may yield a shorter service life, or may even catastrophically fail withresulting personal injury or death. The same goes when heat treatment of parts is notperformed according to design specifications and procedures. Whether a receiver isinitially formed by forging, machining or casting, the finish machining operations areperformed before carburizing, quenching and tempering. If dimensional geometry isincorrect, even a properly heat-treated part made of the correct material will eitherfunction poorly or it will not last as long as it should.Engineering DefinitionsA1 temperature – This is the minimum threshold temperature to create austenitemolecular structure in steel. The A1 temperature is 1341 degrees Fahrenheit for steelwith less than 6.67 % carbon content. All of the steel used in the M14 rifle contains lessthan 1.00 % carbon.12

M14 RIFLE HISTORY AND DEVELOPMENTA3 temperature – The temperature at which ferrite forms as the steel begins cooling. Thisis about 1528 degrees Fahrenheit for AISI 8620 steel.Alloy steel – Alloy steel is steel that contains trace percentages of other elements.Annealing - This is a method of heat treatment performed by heating steel to atemperature that transforms all of the molecules to austenite structure, followed by slowfurnace cooling. This method produces a coarse pearlite molecular structure in the steel.Annealing is done to produce lower strength and higher ductility steel—performancecharacteristics opposite of high strength and brittleness.Austenite – Austenite is the Face Centered Cubic molecular structure of iron. Themaximum solubility of carbon in austenite is 2.11 %.Carburizing – Carburizing is a group of techniques for heat treating the surface of steel.It is used when the alloy steel has insufficient carbon to attain the desired surfaceproperties through conventional heating methods. Carburizing alters the chemistry of thesurface of the steel. The first part of the process is the diffusion of carbon into the part’ssurface at an elevated temperature. This creates a high carbon content at the surfacewhich increases the hardness. When the part is then rapidly cooled and tempered thesurface remains hard and strong while the core (or center) remains softer and tougher.Case depth – The depth below the surface of a steel part to which hardening occurs bysurface heat treatment techniques.Cementite – This is a hard and brittle compound of three iron atoms and one carbonatom. It contains 6.67 % carbon. It is used to strengthen steel when it is dispersedevenly. The chemical formula is Fe3C.Ferrite – Ferrite is the Body Centered Cubic form of iron. The maximum solubility ofcarbon in (alpha) ferrite is 0.0218 %. Alpha ferrite is one structure of several that canform upon slow cooling from the molten phase.Hardness – Hardness can be thought of as resistance to permanent indentation.Hardness is measured using various tests with their own number scales, such as Brinell,Knoop, Rockwell, and Vickers.Heat treatment – Heat treatment is the controlled heating and cooling of metals for thepurpose of changing their physical properties. It is one of many methods that can beused to change the mechanical properties of metals.Hypoeutectoid steel – This is steel with less than 0.77 % carbon content. If hypoeutectoidalloy steel is heated above the A1 temperature, 100 % austenite structure can be formed.This is desired for making hardened steel parts by heat treatment.13

LEE EMERSONMagnetic particle inspection – Magnetic particle inspection is a method of non-destructiveexamination that detects surface and subsurface flaws in ferromagnetic metals (iron,steel, nickel and cobalt alloys).Martensite - The Body Centered Tetragonal molecular structure of steel with 0.2 % orgreater carbon content. It is the hardest, strongest and most brittle molecular structure ofsteel. It can be as hard as 65 HRC.Ms – The temperature at which steel begins to form martensite molecules upon rapidcooling. This temperature differs for each alloy steel.M90 – The temperature at which steel is composed of 90 % martensite upon rapidcooling. This temperature differs for each alloy steel.Normalizing – This is a method of heat treatment that is performed by heating steel to atemperature that transforms all of the molecules to austenite structure followed by aircooling or oil quenching and tempering. This treatment produces a fine pearlitemolecular structure in steel. Normalizing is done to control dispersion-strengthening ofthe steel.Pearlite – A form of steel that contains two solid molecular structures of steel, ferrite andcementite. It is created when steel is slowly cooled.Rockwell hardness test – This hardness tester uses a small diameter steel ball ordiamond cone depending on the material to be sampled. The depth of penetration of theball or cone is automatically measured and converted to a Rockwell hardness number,expressed with “HRC” or “HRD” after the number. HRC means the hardness value on theRockwell C scale. HRD stands for the hardness value on the Rockwell D scale. TheRockwell C and D scales are used to measure the hardness of high strength steels. Adiamond cone indenter is used for these hardness scales.Stress – Applied force divided by the original material cross-section area.Surface hardening - Surface hardening is a process which increases the wear resistanceof a steel part while it retains its softer and tougher interior. There are three methods forraising surface hardness of steel: 1) diffusion 2) applied energy and 3) surface finish.Carburizing and nitrocarburizing are examples of surface hardening by the diffusionmethod. Applied energy techniques for hardening steel surfaces include flame hardeningand induction hardening. Chromium plating and physical vapor deposition are populartypes of surface finishes for steel parts.Tempering – Tempering is the heating of martensite steel below the A1 or eutectoidtemperature. This heating redistributes the cementite within the martensite.Redistribution or dispersion of the cementite is called dispersion-strengthening.14

M14 RIFLE HISTORY AND DEVELOPMENTTempering relieves residual stresses caused by the transformation of austenite intomartensite upon rapid cooling. Tempering reduces the strength and hardness butincreases the ductility and toughness of steel. However, the hardness is also dependentupon the carbon content of the steel. The higher the carbon content the higher thehardness of the martensite.Tensile strength – The strength of a material can be determined by measuring the stressit takes to cause deformation. The yield strength is the stress needed to begin permanentdeformation (elongation) of a material. The ultimate tensile strength is the maximumapplied stress before the material breaks.Toughness – Mathematically, it is often measured as the total area under the stressversus strain curve for a given material. In layman’s terms, toughness is the resistance ofa material to failure by impact.AISI 4100 and 8600 Series Alloy SteelsIn the United States, types of steel are commonly identified by the American Iron andSteel Institute (AISI) classification system. Carbon and alloy steels are given unique fourdigit numbers. The first digit of each number indicates the major alloying element orelements. The second digit represents a subgroup of the major alloy element orelements. The third and fourth digits denote the amount of carbon in the steel. Forexample, AISI 4140 is a molybdenum-chromium alloy steel with 0.40 % carbon content.AISI 4100 and 8600 series alloy and AISI 416 stainless steels are commonly used in themanufacture of M14 rifle parts.Table 1: Elements of Alloy SteelsElement of Alloy SteelAdvantages and Disadvantagescarbonincreases hardness, strength and brittlenesschromiumincreases hardenability and corrosion and wearresistanceironprincipal element of steelmanganeseincreases hardenability by 1) lowering transformationpoints and causing those transformations to be sluggish2) counteracts the brittleness effect from sulfurmolybdenumprevents grain growth resulting in uniformity of hardnessand high strengthnickelincreases toughness, ductility and corrosion resistancephosphorusimproves strength and machinability but has to be limitedto prevent brittleness15

LEE EMERSONsiliconimproves hardness and corrosion resistancesulfurimproves machinability but increases brittlenessvanadiumincreases strength while retaining ductilityTable 2: Composition of AISI 8620, AISI 4140 and AISI 416 SteelsElement ofCompositionAISI 8620 AlloySteelAISI 4140 AlloySteelAISI 416 StainlessSteelcarbon0.18 to 0.23 %0.38 to 0.43 %0.15 %chromium0.4 to 0.6 %0.8 to 1.1 %13 %ironmajor elementmajor elementmajor elementmanganese0.7 to 0.9 %0.75 to 1.0 %1.25 % maximummolybdenum0.15 to 0.25 %0.15 to 0.25 %0.6 % maximumnickel0.4 to 0.7 %phosphorus0.035 % maximum0.035 % maximum0.06 % maximumsilicon0.15 to 0.35 %0.15 to 0.35 %1.0 % maximumsulfur0.04 % maximum0.04 %0.15 % minimumTable 3: Properties of AISI 8620, AISI 4140 and AISI 416 SteelsPropertyAISI 8620Alloy SteelAISI 4140Alloy SteelAISI 416Stainless Steeldensity (lb/in3)0.2830.280.28specific gravity7.87.837.7specific heat (BTU/lb/degrees F)0.10.1140.11melting point (degrees F)260025802714thermal conductivity (BTU-in/ft2-hdegrees F)180.3159.5172.6mean coefficient of thermal6.675.5313329expansion (x10-6in/in/degree F)modulus of elasticity in tension(x 106 psi)16

M14 RIFLE HISTORY AND DEVELOPMENTM14 Rifle PreservationCorrosion – In layman’s terms, corrosion is the wasting away of a material. This is notdesirable but the M14 type rifle must be expected to perform in harsh environments.Thus, corrosion is an issue of concern in its design and application. Corrosion of metalparts can occur from contact from various sources such as chemicals, water immersion,humid air, human body sweat, salt water spray or microbes. Fine grain dust that is high insalts and carbonates, such as that found in Iraq, can corrode metal parts. Alloyaluminum, carbon steel and alloy steel surfaces will oxidize (rust) in moist air but atvarying rates. Carbon and low alloy steels have similar poor corrosion resistance inaerated neutral pH water and sea water. Rubber and plastic materials are not immunefrom corrosion either. Corrosion of rubber and plastic can cause cracking or softening ofrifle parts.Stainless steels have good resistance in mild environments but are susceptible tolocalized chloride pitting corrosion from sources like salt water or body sweat. Thissusceptibility to chloride pitting corrosion is at its greatest when stainless steel is heatedto a temperature around 195 degrees Fahrenheit, e.g., the M14 gas cylinder after firing.Martensitic stainless steels are used to manufacture some M14 type rifle parts.Martensitic stainless steels have the least corrosion resistance of the five types ofstainless steels. In sea water or in water near neutral pH, martensitic AISI 416 stainlesssteel will suffer general surface corrosion at a faster rate than carbon steel or low alloysteel. Martensitic stainless steels are also susceptible to hydrogen embrittlementcracking corrosion but this is not an issue when in service as a M14 type rifle part.Preservation – Carbon and alloy steels can be preserved with coating or plating. MostM14 type rifle parts are made from alloy steels. Alloy steel parts are almost alwayscoated with manganese phosphate or zinc phosphate for corrosion protection. Bothmethods of phosphate coating have been in use for decades.Thomas Coslett developed and patented iron phosphate coating in 1907. Six years later,Frank Richards of the United Kingdom pate

M14 Rifle Lubrication 21 M14 Receiver Material 37 AISI 8620 Alloy Steel 40 How was the U. S. Government Issue M14 receiver made? 41 Receiver Heat Treatment 42 Development of Magnetic Particle Inspection 44 USGI Receiver Geometry 44 Intervening Rifle Mode