The 5.56 X 45mm “Timeline” – 1971

A Chronology of Development by Daniel E. Watters



M16A1 rifles begin to ship with chromed bores and chambers. Previously, only the chambers were chromed.

ARES, Inc. is co-founded by Gene Stoner and Bob Bihun.

WECOM issues “Commodity MA Plan for Rifle 5.56mm M16/M16A1 & Grenade Launcher 40mm M203.”

Frankford Arsenal publishes “Semiempirical Model for Predicting the Upper Size of Solid Particles Migrating from the Barrel to the Gas Tube of the M16A1 Rifle.”

The US provides a military assistance grant of 38,468 M16A1, 64 XM177-type, and 43 XM148 to South Vietnam.

The US provides a military assistance grant of 18,880 M16A1 to Laos.

The US provides a military assistance grant of 99,022 M16A1 to Cambodia.

The US provides 15,000 M16A1 to Indonesia as part of a military assistance package.

The US provides 21,000 M16A1 to Jordan as part of a military assistance package.

The Philippine government requests proposals from foreign firms to establish a domestic 5.56mm rifle plant. Proposals are reportedly submitted by Colt, ArmaLite, Beretta, CETME, IMI, FN, and HK.

Malaysia enters negotiations to purchase 20,000 M16 and five million rounds of 5.56mm ammunition.

The National Board for the Promotion of Rifle Practice (NBPRP) approves the M16 and the civilian Colt AR-15 for use in their rifle matches. (Rules and Regulations For National Matches: Change 2 to AR920-30)

The Swiss introduce the 5.56x48mm Eiger, a cartridge roughly in size to the .22-250. It is intended for military rifle experiments.

Hughes submits an unsolicited proposal to ARPA for a light machine gun using its proprietary “chiclet” cartridges.

The USASASA produces the concept of a Dual Cycle Rifle (DCR), a weapon in which a burst is fired at a very high rate while feed and extraction occur at a fraction of the speed. The DCR is the brainchild of USASASA commander Colonel Raymond S. Isenson and Technical Director Leonard R. Ambrosini. Fifteen companies eventually submit proposals and two are accepted. Multiple barrel designs are rejected due to weight and bulk. The winning proposals instead apply revolver cannon technology: a single barrel combined with a multiple chamber cylinder. The cylinder is fed from a box magazine holding three individual rows of cartridges. During the feed cycle, the top three rounds are simultaneously stripped into individual chambers. One design uses an asymmetrical three-chamber cylinder while the other uses a symmetrical nine-chamber cylinder. By 1973, the prototypes reportedly achieve cyclic rates of ~4,500 rounds per minute in three-round bursts.

The Brazilian Air Force purchases 15,000 HK 33.

MAS completes ten 5.56mm rifle prototypes. These are known as the A1.

The 40mm M433 HEDP grenade cartridge is type-classified as “Standard A”.

The Commanding General of CONARC orders all major commands to field at least one M16A1 rifle team for the US Army’s championships.

Aberdeen’s BRL publishes the report “Sensitivity Study of Rifle Gas Systems.” Results of a sensitivity study of the M16 rifle gas system are presented; this study is based on a simulation of rifle gas system operation developed in the BRL. The calculations indicate that thermodynamic variables in the bolt carrier cavity are only weakly sensitive to variations in the following parameters: pressure and temperature in the gun barrel when the bullet passes the port, friction in the duct flow, and frictional resistance to motion of the bolt carrier. The computational results are sensitive, however, to the chosen origin of time on the oscillogram showing barrel pressure at the port station. Graphs are presented for a typical round illustrating pressure, temperature, density, and piston motion histories for M16 and AR-18 rifle gas systems.

A delegation led by the South Korean Ministry of National Defense’s Assistant Vice Minister for Logistics MG Shin Won Shik visits the US to consult with the DOD and Colt. They conduct final negotiations regarding a M16 co-production agreement.

Admiral McCain requests the support of Secretary of Defense Laird for the Philippine FMS purchase of 4,000 M16. According to the US Ambassador, Philippine President Marcos has requested that delivery be made within 60 days. The US State Department subsequently approves the sale, and indicates that a delivery date of February 28 could be met as long as the Philippine government signs the DOD Letter of Offer and submits payment by January 29. The Philippine government beats the deadline with the submission of a check for $780,042.38.

Aberdeen publishes the report “Product Improvement Test of Quadrant Sight for the M203 Grenade Launcher.” The sight was inspected for physical characteristics, fired for accuracy, and subjected to high and low temperatures, and to ruggedness and lubricants and solvents compatibility tests. No deficiencies were encountered; four shortcomings, however, were experienced. Three shortcomings were similar to shortcomings on the present standard quadrant sight. It was concluded that over-all performance of the test sight was equal to that of the standard sight and that neither was correctly calibrated to impact grenades at the 300 and 375-meter ranges when using ammunition with a velocity level in the lower limit of acceptability for the M203 grenade launcher. It is recommended that action be taken to produce ammunition with a velocity level of 245 +/- 5 fps from the M203 launcher, or that the sight (test or standard) be recalibrated for 40mm ammunition in the lower limit of allowable velocity acceptability (235 fps).

Comprehensive Designers Inc. publishes the report “Limit Dimensional Study of the M203 Grenade Launcher, M16, M16A1 Rifles and Quadrant Sight Combinations.”

HK hedges its bets with the introduction of a more conventional micro-caliber rifle, the HK 36 (not to be confused with the later G36). Its 4.6x36mm cartridge is the product of the joint Spanish/German study. It is best known for its asymmetrical “Spoon-nose” projectile: the Löffelspitz. The Löffelspitz is the product of studies by CETME‘s Dr. Günther Voss to find methods to deliberately induce yaw once a projectile strikes flesh, while not adversely effecting its accuracy during flight

Aberdeen’s BRL publishes the report “A Compendium of Ballistic Properties of Projectiles of Possible Interest in Small Arms.” The shapes cover a range of Length/Diameter ratios ranging from conventional bullets (approximately 3.5) to that of fléchette (approximately 20), and include such shapes as cones, cone cylinders, and cone flares. The ballistic properties are mapped over a range of calibers (5.56mm, 6.5mm, and 7.62mm) and projectile densities. A drag-reducing tracer is included as one of the prime design considerations as a means of reducing base drag.

Colt’s John Jorczak and David Behrendt receive US Patent #3,564,950 titled “Cartridge Case Extractor Tool.”

Carroll D. Childers and Joseph C. Monolo file “NWL Technical Report TR-2536” concerning the NWL-Dalhgren’s third model 50-round magazine. The authors recommend that the magazine be adopted and issued one per every deployed SEAL Team member.

Cadillac Gage resubmits the redesigned Stoner 63A1 for renewed Phase 1 testing by WECOM.

ARPA, in conjunction with USASASA, awards TRW Systems a contract to develop an infantry rifle which will require far less maintenance than the issue M16A1. Appropriately, the project is named the “Low Maintenance Rifle” (LMR). An engineering team led by Don Stoehr is assigned to the project. The final design uses a gas-operated, roller-locked action, and bears more than a slight resemblance to the German FG42 paratrooper rifle. Since the weapon fires full-automatic only from an open bolt, the LMR borrows the trigger housing of the M60 GPMG, itself an amalgamation of the FG42 rifle and MG42 GPMG. Besides the 5.56mm models, at least one prototype is chambered for the XM216 SPIW cartridge.

Frankford Arsenal publishes “Packaging Concept Study for 5.56 mm Caseless Ammunition.”

Radway Green delivers its first batch of 5x44mm cartridges.

On behalf of Frankford Arsenal, Colt’s Technik, Inc. publishes “Feasibility Study of Fléchette Fired from Rifled Barrel.” In these experiments, saboted fléchette have been loaded into standard 5.56x45mm cases and fired through M16 rifles. Conceived as a low-cost way of testing different sabot/fléchette designs, the improved accuracy results cast doubt upon the existing SFR weapon and cartridge designs.

The US and South Korean governments sign the M16 co-production Memorandum of Understanding (MOU), which specifies the total quantity of rifles authorized for production in South Korea. This consists of 600,000 complete rifles and 48,000 rifle equivalents in spare parts. The MOU also authorizes $42 million in FMS credits to support production equipment, raw materials, technical assistance, construction, royalty fees, and training. South Korea is prohibited from transferring rifles or components to third parties without the consent of the US, and the MOU can be terminated only by mutual agreement. Licensing and technical assistance agreements are also signed by Colt and the ROK Ministry of National Defense. This implements the MOU, establishes royalty fees, and provides training, production know-how, and technical assistance. South Korea is authorized 100 percent rifle manufacturing capability, involving 124 individual parts ranging from springs to buttstocks. (In contrast, Colt’s factory produces only around 12 parts in house, and the remaining components are subcontracted among 70 vendors.) Full production of 10,000 rifles per month is planned for May 1974, with the completion of the production run expected by February 1979. By the end of the month, the first $15 million in FMS credits is approved for FY 1971.

The military specification for M197 High Pressure Test, MIL-C-46936A(MU), is revised to MIL-C-46936B(MU).

Colt’s John Jorczak receives US Patent #3,568,324 titled “Battlesight for an Auxiliary Projectile Launcher.”

The Chinese PLA‘s logistics department holds the 713 Conference, a research meeting to determine the desired characteristics of a SCHV cartridge.

AAI submits an unsolicited proposal for the development of a plastic cased blank.

More than 1,000 union workers from Colt petition Rep. William R. Cotter (D-CT) to stop the US-Korea M16 co-production agreement. Cotter lobbies the White House in an attempt to stop the plan.

The Colt CMG-2 is submitted for Navy nomenclature assignment.

The Pentagon refuses Rep. Cotter’s Freedom of Information Act request regarding details of the US-Korea M16 co-production agreement.

The CDCIA publishes “Army Small Arms Requirements Study II (ASARS II) Study Plan.”

The Colt CMG-2 is officially designated “Gun, Machine, 5.56 Millimeter, EX 27 Mod 0.”

HK‘s Tilo Möller and Dieter Ketterer file multiple US patent applications for the HK 36’s carrying handle and integrated optic, trigger pack attachment, and ambidextrous charging handle.

Colt’s Stanley Silsby files the report “Lightweight Rifle/Submachine Gun.” The report details the design and fabrication of the four IMP prototypes for the USAF. Demonstrations proved the basic concept of utilizing the shooter’s arm as the gunstock was not only feasible but exceeded expectations. Further efforts will be made to improve trigger pull, trigger guidance, pistol grip locking, the arm rest, sighting, and to modify the design for quantity production.

The CDCIA publishes “Army Small Arms Requirements Study II (ASARS II): First In-Process Review After Action 16 – 17 June 1971.”

The Army Aviation Systems Test Activity publishes the report “5.56/7.62MM Weapons Comparative Evaluation, OH-6A Helicopter.” The objectives of the test were to evaluate and compare the 5.56mm XM214 and the 7.62mm GAU-2B/A automatic guns for firing accuracy and effect of the weapons firing on flight characteristics. Only minor differences were noted in firing accuracy at ranges of 500 meters or less. A pronounced loss of accuracy was noted with the XM214 at ranges of 1000 meters and greater. Helicopter reactions were most apparent, for both weapons, during hover firing at a high rate of fire and were more severe with the GAU-2B/A than with the XM214. At forward airspeeds, only minor differences in flight characteristics were noted during firing of the weapons. Vibration levels of the instrument panel and gun mount were reduced significantly with installation of the XM214.

Rodman Laboratory publishes the report “Concepts of Single Shot Grenade Launchers Attached to an Infantry Rifle.” The report discusses the initial phase of an in-house design activity for the development of a 30mm grenade launcher. The launcher work is one aspect of the total Future Rifle System Program. As such, the conceptual efforts were molded around many of the requirements of that program so as to produce a composite weapon system consisting of both area and point fire components. In a span of ten weeks, a team of five people produced 14 deserving concepts from more than 23 basic approaches. Out of these 14, two concepts were selected for further development and inclusion in the overall Future Rifle System Program. Detailed design activity is currently underway to translate these two concepts to firing hardware for a projected delivery date of Fall 1971.

At Frankford Arsenal, Andrew J. Grandy and Martin Horchler publish”The Encapsulated Folded Ammunition Concept.” The authors have experimented with 5.56mm folded path cartridges in order to duplicate the performance of the M193 cartridge.

HK‘s Tilo Möller and Dieter Ketterer file an US patent application for the HK 36’s semi-integral magazine and loading system.

The Army awards a $365,340 contract to Honeywell to design, fabricate, and build a prototype automated machine line for production of sabots for SPIW fléchette cartridges.

Rep. Cotter proposes legislation that would bar foreign production of US weapons without authorization by Congress. The House Foreign Affairs Committee rejects Cotter’s proposal.

$10 million in FMS credits are approved for South Korean M16 production in FY 1972.

Twin Cities AAP issues the memo “5.56mm Production Equipment Based on New Concept for Manufacture of Small Caliber Ammunition.”

Reynolds Metals publishes the report “Development of Aluminum Alloys for Cartridge Cases.” The study was aimed at developing an aluminum alloy suitable for use in a 5.56mm cartridge case. Two distinctly different types of properties were required. In the annealed condition, the alloy must have good formability, such that the many cup and draw operations can be readily performed without the introduction of defects. In the final heat treated condition the alloy must exhibit both high strength and toughness. Ideally, a yield strength of 80,000 PSI and a tear strength to-yield strength ratio of 1.5 were desired by the Sponsor. Such a combination of properties is not currently available in any known commercial alloy. Variations of the commercial alloys 7075, 7178, and 7001 were studied.

Aberdeen publishes the report “Product Improvement Test of 5.56-MM Gilding-Metal-Clad Steel-Jacketed Tracer Projectiles.”

MIL-STD-1453(MU), the military standard for the ballistic standards and test method for evaluating and selecting 5.56mm ammunition for M16/M16A1 weapon acceptance tests, is published.

Frankford Arsenal begins computerized parametric design analyses to design a cartridge from scratch to meet the SAW requirements. Five candidate designs are considered. These include a 6.5mm fléchette cartridge, and 5.56mm, 6mm, 6.35mm, and 6.5mm cartridges using conventional bullets.

WECOM publishes the report “Chromium Plating of Caliber .17 (4.32mm) Barrels.” Caliber .17 (4.32mm) barrel blanks were machined to the exterior contour of an M16 Rifle barrel. Attempts to chromium plate these barrels with conventional plating fixtures were unsuccessful because misalignment of the electrode caused discoloration and shading of the plating. Attempts to obtain satisfactory, chromium-plated bores by use of better electrode alignment with the conventional fixtures were also unsuccessful. A self-aligning rotating electrode fixture was fabricated, and a technique for chromium-plating the caliber .17 bore was established. With the use of the rotating electrode fixture, many of the problems were eliminated that were encountered with the conventional fixtures on the caliber .17 bore.

The Office of Product Manager, M16 Series Rifles is disbanded. The staff is reassigned within WECOM.

WECOM publishes the report “Procurement History and Analysis of M16 Rifle.”

Aberdeen’s BRL publishes the report “Comparison of a Theoretical and Experimental Study of the Gas System in the M16A1 Rifle.” Results of the study show that functioning of the rifle is quite sensitive to variations in gas port diameter, initial volume, and effective pressure area in the gas system. However, functioning is quite insensitive to variations in leakage area, vent area, and the distance the bolt carrier travels before uncovering the vent holes in the gas system. The study concludes there is no great advantage in changing any parameter in the M16 gas system.

COMUSKOREA advises Admiral McCain that a MOU will be negotiated between the South Korean MND and the DOD for FMS credits for converting and expanding the ROK arsenal for ammunition production.

Frankford Arsenal releases the report “An Analysis of Local Temperature Profiles Encountered in the Aluminum Cartridge Case Drilled Hole Experiment.” In order to gain a better understanding of the failure phenomenon experienced with aluminum cases, a combination experimental and theoretical program was initiated to study the failure dynamics using intentionally induced failures in 5.56mm aluminum cases.

Military Characteristics for Plastic 5.56mm Blank Cartridge” is published.

Frankford Arsenal narrows its SAW cartridge studies to 5.56mm and 6mm. The 5.56mm candidate design is based on a case 1.949″ long and 0.4313″ wide, loaded with a lead core 68gr bullet. The 6mm candidate design is based on a case 1.715″ long and 0.372″ wide, loaded with a steel core 80gr bullet. (Note that this case is actually smaller than the standard 5.56x45mm.)

The US Army Arctic Test Center issues the report “Service Test of Launcher, Grenade, 40mm, M203, Attachment for Rifles, under Arctic Winter Conditions.” The M203 is found unsuitable for arctic use due to two deficiencies: fracture of the barrel guide during firing and failure of the adhesive bond between the handguard and the barrel. The latter problem had already been identified as an issue during 1969 testing at Aberdeen.

Colt’s Stanley Silsby files a patent application for a rate reducer for the IMP.

WECOM publishes the report “Evaluation of Experimental Drive Springs for the XM19 Rifle.” Laboratory tests and a theoretical study were conducted to determine the optimum design for increasing the life of the XM19 drive spring. Spring endurance tests were conducted by the Research Directorate of the Weapons Laboratory at Rock Island. Fatigue properties of eight experimental drive spring designs were evaluated under simulated firing conditions. The experimental springs consisted of various materials and strand constructions of three, seven, or 14 wires. A theoretical study was performed by the University of Illinois under direction of the Research Directorate on the dynamic response of helical compression springs. Theoretical and experimental data were correlated and were in close agreement. It is determined from this investigation that of the eight experimental designs that were evaluated, the two-piece spring assembly is superior because it retained maximum loads at the completion of the endurance tests.

WECOM completes Phase 1 testing of the redesigned Stoner 63A1.

Frankford Arsenal begins work on developing actual 6mm cartridge cases based on its computerized SAW model. Minor dimensional changes are made to accommodate existing equipment and case components (5.56x45mm 2nd draw pieces).

The M203 grenade launcher’s military specification, MIL-L-45935, is issued.

On behalf of the US Army, Harold H. Wiese receives US Patent #3,603,020 titled “Magazine Assembly with Expendable Cartridge Container Unit.”

Stanley Silsby, on behalf of the US Army, receives US Patent #3,604,142 titled “Four-Stack Cartridge Magazine.”

MUCOM Commanding General BG Graham issues a directive that the SAW cartridge cases be made of an alternative material other than brass, such as steel or aluminum. This change is in order to fully comply with the spirit of the DOD‘s copper conservation policy.

Colt’s Henry Into files a patent application for the design of the SCAMP.

Dale M. Davis receives US Patent #3,611,872 titled “Lightweight Compact Rifle.”

The Connecticut Citizens Action Group, an organization affiliated with Ralph Nader, release a report titled “The M16: Colt’s Lethal Lemon.” It charges that Colt has deliberately circumvented Army quality control requirements in the production of the M16. The House Armed Services Committee staff begins a probe.

The US Army, through the Land Warfare Laboratory at Aberdeen, signs a contract with AAI for the development of their proposed plastic case blank.

Colt’s Robert Fremont receives US Patent #3,619,929 titled “Magazine with Anti-Double-Feed Indentations in the Side Walls.”

Colt’s Henry Into and John Jorczak receive US Patent #3,618,248 titled “Buttstock Assembly with a Latchable Door for a Compartment Formed Therein.”

Frankford Arsenal begins work on developing actual 5.56mm cartridge cases based on its computerized SAW model. Minor dimensional changes are made to accommodate existing equipment and case components (7.62mm NATO final draw pieces trimmed to 1-3/8″).

Frankford Arsenal publishes drawings of the initial 6mm SAW case as Sketch BCX-1: 6MM Brass Case (Special). Approximately 800 cases are fabricated to this design. These are held back awaiting design of the 80gr bullet. (It appears that the 80gr bullet was never designed, and that these cases were never loaded.)

Colt submits an unsolicited proposal to the US Army for the Small Caliber Machine Pistol (SCAMP). The Colt SCAMP fires a short .224″ caliber proprietary cartridge known as the .22 SCAMP.

Thailand contracts with HK for the construction of a HK 33 manufacturing plant.

Rep. Howard claims that the FBI is investigating allegations that Colt has “deliberately cheated” on factory tests of the M16. The FBI will only confirm that an inquiry is in progress.

$5 million in FMS credits for South Korean domestic ammunition production are approved for FY 1972.

The Naval Training Device Center publishes the report “Clothing Penetration Tests for the M16 Training Cartridge.” The report indicates that trainees are not adequately protected against stray projectiles based on penetration tests for the M16 training cartridge.

Fairchild Industries’ John F. Dealy and Michael W. York file a patent application for a low profile set of M16 sights that are viewed through the struts of the carrying handle.

USMC Commandant General Chapman directs that the contract to Cadillac Gage to design and produce the Stoner 63A1 required for Phase 2 testing at Aberdeen be terminated at no cost to the Government. With this, production of the Stoner 63A1 ends.

Colt’s George Curtis and Henry Tatro file patent applications for the design of the CMG-2.

Physics Technology Labs publishes the report “Feasibility Study of the Sputtering of Coatings Onto the 4.32mm Barrel Bore.” The research is under contract to the USASASA.

Frankford Arsenal begins limited fabrication of the 5.56mm SAW cartridge case. Approximately 100 cases are made through January 1972. These are held back waiting for the procurement of the 68gr bullets and a special test barrel.

Col. Raymond S. Isenson of the USASASA rejects Colt’s SCAMP proposal as the US Army is experimenting with a parallel small arms program called the “Personal Defense Weapon” (PDW).

(Next: 5.56mm 1972)

by Daniel E. Watters, Small Arms Historian
Post questions or comments at The 5.56mm Timeline’s Facebook page.

Document History
Publication: 12/10/1998
Last Revised: 05/17/2009


Author’s Note
This article was originally published at The Gun Zone — The Gunperson’s Authoritative Internet Information Resource. My friend and mentor Dean Speir has graciously hosted my articles at TGZ for nearly 16 years. These articles would likely have never appeared online without his constant encouragement and assistance. 

With TGZ’s closure in early 2017, Dean encouraged me to find a new home for my scholarship so it wouldn’t be lost in the dustbin of the Internet. Loose Rounds has welcomed me with open arms. In the future, I intend to expand my legacy TGZ articles and add new contributions here at Loose Rounds.


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