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100-520: Long out of production, today they are a coveted collector's item with prices for even the most common model ranging above $ 1,000. They are rarely fired; ammunition is scarce and can cost over $ 200 per round. Robert Mainhardt and Art Biehl joined forces to form MBAssociates, or MBA, in order to develop Biehl's armor-piercing rocket rounds. Originally developed in a .51 caliber , the cartridges were self-contained self-propelled rockets with calibers ranging from .49 and 6mm to 20mm. A family of Gyrojet weapons

200-586: A 10-day state visit to the US . President Eisenhower pledged his continued support, and a parade was held in Diệm's honor. But Secretary of State Dulles privately conceded Diệm had to be backed because they could find no better alternative. Between 1954 and 1957, the Diệm government succeeded in preventing large-scale organized unrest in the countryside. In April 1957, insurgents launched an assassination campaign, referred to as "extermination of traitors". 17 people were killed in

300-648: A Marxist–Leninist political organization which operated primarily in Hong Kong and the Soviet Union . The party aimed to overthrow French rule and establish an independent communist state in Vietnam. In September 1940, Japan invaded French Indochina, following France's capitulation to Nazi Germany . French influence was suppressed by the Japanese, and in 1941 Cung, now known as Ho Chi Minh , returned to Vietnam to establish

400-607: A Military Assistance and Advisory Group (MAAG) to screen French requests for aid, advise on strategy, and train Vietnamese soldiers. By 1954, the US had spent $ 1 billion in support of the French military effort, shouldering 80% of the cost of the war. During the Battle of Dien Bien Phu in 1954, US carriers sailed to the Gulf of Tonkin and the US conducted reconnaissance flights. France and

500-554: A psychological warfare campaign which exaggerated anti-Catholic sentiment among the Viet Minh and distributed propaganda attributed to Viet Minh threatening an American attack on Hanoi with atomic bombs. During the 300-day period, up to one million northerners, mainly minority Catholics, moved south, fearing persecution by the Communists. The exodus was coordinated by a U.S.-funded $ 93 million relocation program, which involved

600-496: A rifled barrel, the distance is measured between opposing lands or between opposing grooves ; groove measurements are common in cartridge designations originating in the United States , while land measurements are more common elsewhere in the world. Measurements "across the grooves" are used for maximum precision because rifling and the specific caliber so measured is the result of final machining process which cuts grooves into

700-692: A " 30 caliber rifle", which could accommodate any of a wide range of cartridges using a roughly 0.30 inches (7.6 mm) projectile; or as a "22 rimfire", referring to any rimfire firearms firing cartridges with a 22 caliber projectile. However, there can be significant differences in nominal bullet and bore dimensions, and all cartridges so "categorized" are not automatically identical in actual caliber. For example, 303 British firearms and projectiles are often "categorized" as ".30-caliber" alongside several dozen U.S. "30-caliber" cartridges despite using bullets of .310–.312-inch (7.87–7.92 mm) diameter while all U.S. "30-caliber" centerfire rifle cartridges use

800-399: A "Gyrojet". In one test, a rocket round punched through an old truck door and into a water-filled 55-gallon drum, almost exiting its opposite side. SOG men also test-fired it through sandbag walls and even tree trunks. Caliber In guns , particularly firearms , but not artillery, where a different definition may apply , caliber (or calibre ; sometimes abbreviated as " cal ")

900-405: A .250 inch land diameter and .257 inch groove diameter. The .308 Winchester is measured across the grooves and uses a .308-in diameter (7.82-mm) bullet; the military-specification version is known as 7.62 × 51 mm NATO , so called because the bore diameter measured between the lands is 7.62 mm, and the cartridge has a case 51 mm long. Converting a rifle to fire a different cartridge in

1000-423: A barrel diameter of roughly 0.45 inches (11.43mm). Barrel diameters can also be expressed using metric dimensions. For example, a "9 mm pistol" has a barrel diameter of about 9 millimeters. Since metric and US customary units do not convert evenly at this scale, metric conversions of caliber measured in decimal inches are typically approximations of the precise specifications in non-metric units, and vice versa. In

1100-464: A ceasefire with the Viet Minh, and independence was granted to Cambodia, Laos, and Vietnam. At the 1954 Geneva Conference, Vietnam was temporarily partitioned at the 17th parallel . Ho Chi Minh wished to continue war in the south, but was restrained by Chinese allies who convinced him he could win control by electoral means. Under the Geneva Accords, civilians were allowed to move freely between

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1200-412: A common, standard .308-inch (7.82 mm) bullet outside diameter. Using bullets larger than design specifications causes excessive pressures, while undersize bullets cause low pressures, insufficient muzzle velocities and fouling that will eventually lead to excessive pressures. Makers of early cartridge arms had to invent methods of naming cartridges since no established convention existed then. One of

1300-630: A coordinated uprising in South Vietnam against the government and a third of the population was soon living in areas of communist control. In December 1960, North Vietnam formally created the Viet Cong (VC) with the intent of uniting all anti-GVN insurgents, including non-communists. It was formed in Memot, Cambodia , and directed through COSVN. The VC "placed heavy emphasis on the withdrawal of American advisors and influence, on land reform and liberalization of

1400-432: A distance of 26 mi (42 km). Smoothbore cannon and carronade bores are designated by the weight in imperial pounds of spherical solid iron shot of diameter to fit the bore. Standard sizes are 6, 12, 18, 24, 32, and 42 pounds, with some non-standard weights using the same scheme. See Carronade#Ordnance . From about the mid-17th until the mid-19th century, the measurement of the bore of large gunpowder weapons

1500-512: A more "modest" winning margin of "60 to 70 percent." Diệm, however, viewed the election as a test of authority. He declared South Vietnam to be an independent state under the name Republic of Vietnam (ROV), with him as president. Likewise, Ho Chi Minh and other communists won at least 99% of the vote in North Vietnamese "elections". The domino theory , which argued that if a country fell to communism, all surrounding countries would follow,

1600-592: A multiple of the bore diameter. For example, a 4-inch gun of 50 calibers would have a barrel 4 in × 50 = 200 in long (written as 4" L/50 or 4"/50). A 16-inch gun of 50 calibers (16" L/50) has a barrel length of 50 × 16 = 800 inches (66 ft 8 in). Both 14-in and 16-in navy guns were common in World War II. The British Royal Navy insisted on 50-cal guns on ships as it would allow 1,900 to 2,700 lb (860 to 1,220 kg) shells to travel at an initial velocity of up to 1,800 mph (2,897 km/h) to

1700-542: A person knowledgeable in Indochinese affairs who did not agree that had elections been held as of the time of the fighting, possibly 80% of the population would have voted for the Communist Ho Chi Minh as their leader rather than Chief of State Bảo Đại. Indeed, the lack of leadership and drive on the part of Bảo Đại was a factor in the feeling prevalent among Vietnamese that they had nothing to fight for. According to

1800-463: A policy of " Vietnamization " from 1969, which saw the conflict fought by an expanded ARVN, while US forces withdrew. A 1970 coup in Cambodia resulted in a PAVN invasion and a US–ARVN counter-invasion , escalating its civil war. US troops had mostly withdrawn from Vietnam by 1972, and the 1973 Paris Peace Accords saw the rest leave. The accords were broken almost immediately and fighting continued until

1900-482: A pound; therefore, its barrel is smaller than the 12-gauge. This metric is used in Russia as "caliber number": e.g., "shotgun of the 12 caliber." The 16th caliber is known as "lordly" ( Russian : барский ). While shotgun bores can be expressed in calibers (the .410 bore shotgun is measured as .410 in (10.4 mm) in diameter, unlike with rifles the actual bore diameter of a smoothbore shotgun varies significantly down

2000-432: A related expression. The gauge of a shotgun refers to how many lead spheres, each with a diameter equal to that of the bore, that amounts to one pound (454 g (1.0 lb)) in weight. In the case of a 12-gauge (18.5 mm) shotgun, it would take 12 spheres the size of the shotgun's bore to equal a pound. A numerically larger gauge indicates a smaller barrel: a 20-gauge (15.6 mm) shotgun requires more spheres to equal

2100-447: A removable magazine; rounds had to be pushed down from the open "bolt" and then held in place by quickly sliding a cover over them on the top of the gun. Reloading quickly was impossible. Tests in 2003 claimed that the acceleration, rather than being constant, started at a high value and decreased, leading to velocities at close range which were not as low as expected, about 100 ft/s (30 m/s) at 1 foot (30 cm) instead of

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2200-432: A rocket has maximum kinetic energy immediately after its fuel is expended. The burn time for a Gyrojet rocket has been reported as 1 ⁄ 10 of a second by a Bathroom Reader's Institute book and as 0.12 second by "The 'DeathWind' Project". A firearm's rifled barrel must be manufactured to high precision and be capable of withstanding extremely high pressures; it is subject to significant wear in use. The Gyrojet rocket

2300-677: A solution due to the possibility of large government contracts , Minchakievich then invented diagonal vented ports to make the projectiles or ammunition spin while advancing, stabilizing the projectiles gyroscopically , in the same manner as a rifle. This method was used in all the Mainhardt calibers for the Gyrojet. Minchakievich warned Mainhardt that rushing the project would only make the pistol shoddy and unreliable. Working for free out of his Livermore Aerospace Plastics Lab, Minchakievich requested six more months to perfect an accurate projectile, and make

2400-495: Is based. The following table lists some of the commonly used calibers where both metric and US customary units are used as equivalents. Due to variations in naming conventions, and the whims of the cartridge manufacturers, bullet diameters can vary widely from the diameter implied by the name. For example, a difference of 0.045 in (1.15 mm) occurs between the smallest and largest of the several cartridges designated as ".38 caliber". Shotguns are classed according to gauge,

2500-410: Is fired through a simple straight, smooth-walled tube of no great strength. Accuracy is increased by spinning the projectile. This is achieved for a bullet by being forced against spiral rifling grooves in the barrel. A rocket does not have enough initial energy to allow stabilization this way. Spin stabilization of the Gyrojet was provided by angling the four tiny rocket ports rather than by forcing

2600-419: Is much variance in the use of the term "small-bore", which over the years has changed considerably, with anything under 0.577 inches (14.7 mm) considered "small-bore" prior to the mid-19th century. While modern firearms are generally referred to by the name of the cartridge the gun is chambered for, they are still categorized together based on bore diameter. For example, a firearm might be described as

2700-551: Is possible this rifle was chambered in the 6 mm caliber. Came with a rifle type stock, pistol grip and scope. Derringer pistol with an upper barrel chambered for the Gyrojet round. The Gyrojet principle was also examined for use in survival flare guns, and a similar idea was explored for a grenade launcher . The emergency-survival flare version (A/P25S-5A) was used for many years as a standard USAF issue item in survival kits, vests, and for forward operations signaling, with flares available in white, green, blue, and red. Known as

2800-634: Is the most commonly used title in English . It has been called the Second Indochina War since it spread to Laos and Cambodia , the Vietnam Conflict , and Nam (colloquially 'Nam). In Vietnam it is commonly known as Kháng chiến chống Mỹ ( lit.   ' Resistance War against America ' ). The Government of Vietnam officially refers to it as the Resistance War against America to Save

2900-520: Is the specified nominal internal diameter of the gun barrel bore – regardless of how or where the bore is measured and whether the finished bore matches that specification. It is measured in inches or in millimeters . In the United States it is expressed in hundredths of an inch; in the United Kingdom in thousandths; and elsewhere in millimeters. For example, a US " 45 caliber " firearm has

3000-516: The 1975 spring offensive and fall of Saigon to the PAVN, marking the war's end. North and South Vietnam were reunified in 1976. The war exacted enormous human cost : estimates of Vietnamese soldiers and civilians killed range from 970,000 to 3 million. Some 275,000–310,000 Cambodians , 20,000–62,000 Laotians , and 58,220 US service members died. Its end would precipitate the Vietnamese boat people and

3100-597: The Châu Đốc massacre at a bar in July, and in September a district chief was killed with his family. By early 1959, Diệm had come to regard the violence as an organized campaign and implemented Law 10/59, which made political violence punishable by death and property confiscation. There had been division among former Viet Minh, whose main goal was to hold elections promised in the Geneva Accords, leading to " wildcat " activities separate from

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3200-645: The Cold War between the Soviet Union and US. Direct US military involvement greatly escalated from 1965 until its withdrawal in 1973. The fighting spilled over into the Laotian and Cambodian Civil Wars , which ended with all three countries becoming communist in 1975. After the defeat of French Indochina in the First Indochina War that began in 1946, Vietnam gained independence in the 1954 Geneva Conference but

3300-777: The Cuban Missile Crisis (October 1962) played out on television worldwide. It was the closest the Cold War came to nuclear war . The Kennedy administration remained committed to the Cold War foreign policy inherited from the Truman and Eisenhower administrations. In 1961, the US had 50,000 troops based in South Korea, and Kennedy faced four crisis situations: the failure of the Bay of Pigs Invasion he had approved in April, settlement negotiations between

3400-555: The French Navy and the US Seventh Fleet to ferry refugees. The northern refugees gave the later Ngô Đình Diệm regime a strong anti-communist constituency. Over 100,000 Viet Minh fighters went to the north for "regroupment", expecting to return south within two years. The Viet Minh left roughly 5,000 to 10,000 cadres in the south as a base for future insurgency. The last French soldiers left South Vietnam in April 1956 and

3500-651: The Ho Chi Minh trail to supply and reinforce the VC. By 1963, the north had covertly sent 40,000 soldiers of its own People's Army of Vietnam (PAVN), armed with Soviet and Chinese weapons, to fight in the insurgency in the south. President John F. Kennedy increased US involvement from 900 military advisors in 1960 to 16,300 in 1963 and sent more aid to the Army of the Republic of Vietnam (ARVN), which failed to produce results. In 1963, Diem

3600-638: The Korean War in June convinced Washington policymakers that the war in Indochina was another example of communist expansionism, directed by the Soviet Union. Military advisors from China began assisting the Viet Minh in July 1950. Chinese weapons, expertise, and laborers transformed the Viet Minh from a guerrilla force into a regular army. In September 1950, the US further enforced the Truman Doctrine by creating

3700-608: The Pentagon Papers , which commented on Eisenhower's observation, Diệm would have been a more popular candidate than Bảo Đại against Hồ, stating that "It is almost certain that by 1956 the proportion which might have voted for Ho - in a free election against Diem - would have been much smaller than 80%." In 1957, independent observers from India, Poland, and Canada representing the International Control Commission (ICC) stated that fair elections were impossible, with

3800-587: The Viet Minh , an anti-Japanese resistance movement that advocated for independence. The Viet Minh received aid from the Allies , namely the US, Soviet Union, and Republic of China . Beginning in 1944, the US Office of Strategic Services (O.S.S.) provided the Viet Minh with weapons, ammunition, and training to fight the occupying Japanese and Vichy French forces. Throughout the war, Vietnamese guerrilla resistance against

3900-511: The British were opposed. Eisenhower, wary of involving the US in an Asian land war, decided against intervention. Throughout the conflict, US intelligence estimates remained skeptical of France's chance of success. On 7 May 1954, the French garrison at Dien Bien Phu surrendered. The defeat marked the end of French military involvement in Indochina. At the Geneva Conference , they negotiated

4000-452: The GVN, on coalition government and the neutralization of Vietnam." The identities of the leaders of the organization were often kept secret. Support for the VC was driven by resentment of Diem's reversal of Viet Minh land reforms in the countryside. The Viet Minh had confiscated large private landholdings, reduced rents and debts, and leased communal lands, mostly to poorer peasants. Diem brought

4100-528: The Gyrojet more famous than the Colt Peacemaker. Mainhardt and the Air Force declined as current ordnance and technology was in demand for Vietnam. Minchakievich even attempted a marketing strategy by enlisting the help of Gene Roddenberry in using the pistol on Star Trek. Although Roddenberry loved the Gyrojet, he wanted a "ray gun" and not a pistol that merely shot a rocket projectile, no matter how advanced for

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4200-576: The ICC reporting that neither South nor North Vietnam had honored the armistice agreement. From April to June 1955, Diệm eliminated political opposition in the south by launching operations against religious groups: the Cao Đài and Hòa Hảo of Ba Cụt . The campaign also attacked the Bình Xuyên organized crime group, which was allied with members of the communist party secret police and had military elements. The group

4300-464: The Japanese grew dramatically, and by the end of 1944 the Viet Minh had grown to over 500,000 members. US President Franklin D. Roosevelt was an ardent supporter of Vietnamese resistance, and proposed that Vietnam's independence be granted under an international trusteeship following the war. Following the surrender of Japan in 1945, the Viet Minh launched the August Revolution , overthrowing

4400-649: The Japanese-backed Empire of Vietnam and seizing weapons from the surrendering Japanese forces. On September 2, Ho Chi Minh proclaimed the Declaration of independence of the Democratic Republic of Vietnam (DRV). However, on September 23, French forces overthrew the DRV and reinstated French rule. American support for the Viet Minh promptly ended, and O.S.S. forces left as the French sought to reassert control of

4500-624: The Nation. It is sometimes called the American War . Vietnam had been under French control as part of French Indochina since the mid-19th century. Under French rule, Vietnamese nationalism was suppressed, so revolutionary groups conducted their activities abroad, particularly in France and China. One such nationalist, Nguyen Sinh Cung , established the Indochinese Communist Party in 1930,

4600-455: The PRC also completed its withdrawal from North Vietnam. Between 1953 and 1956, the North Vietnamese government instituted agrarian reforms, including "rent reduction" and "land reform", which resulted in political oppression. During land reform, North Vietnamese witnesses suggested a ratio of one execution for every 160 village residents, which extrapolates to 100,000 executions. Because the campaign

4700-516: The State of Vietnam, with Bảo Đại as Emperor, and Ngô Đình Diệm as prime minister. Neither the US, nor Diệm's State of Vietnam, signed anything at the Geneva Conference. The non-communist Vietnamese delegation objected strenuously to any division of Vietnam, but lost when the French accepted the proposal of Viet Minh delegate Phạm Văn Đồng , who proposed Vietnam eventually be united by elections under

4800-508: The US discussed the use of tactical nuclear weapons , though reports of how seriously this was considered and by whom, are vague. According to then-Vice President Richard Nixon , the Joint Chiefs of Staff drew up plans to use nuclear weapons to support the French. Nixon, a so-called " hawk ", suggested the US might have to "put American boys in". President Dwight D. Eisenhower made American participation contingent on British support, but

4900-420: The United States military, most Gyrojets were sold on the commercial market starting in the mid-1960s. These were Mark I Gyrojets, which launched a .51 caliber rocket, and had ammunition that was costly to produce and buy. In 1968, the U.S. Gun Control Act of 1968 created a new legal term, the destructive device . Under the new law, any weapon firing an explosive-filled projectile over a half-inch in diameter

5000-522: The Vienna summit with Khrushchev, "Now we have a problem making our power credible and Vietnam looks like the place." Kennedy's policy toward South Vietnam assumed Diệm and his forces had to defeat the guerrillas on their own. He was against the deployment of American combat troops and observed "to introduce U.S. forces in large numbers there today, while it might have an initially favorable military impact, would almost certainly lead to adverse political and, in

5100-443: The barrel with low energy, and accelerates until the fuel is exhausted at about 60 feet (18 metres), at which point the 180-grain rocket has a velocity of about 1250 feet per second (380 m/s), slightly greater than Mach one, with about twice as much energy as the common .45 ACP round. While test figures vary greatly, testers report that there was a sonic crack from some rounds, but only a hissing sound from others, suggesting that

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5200-842: The border. About 500 of the "regroupees" of 1954 were sent south on the trail during its first year of operation. The first arms delivery via the trail was completed in August 1959. In April 1960, North Vietnam imposed universal military conscription for men. About 40,000 communist soldiers infiltrated the south from 1961 to 1963. In the 1960 U.S. presidential election , Senator John F. Kennedy defeated incumbent Vice President Richard Nixon. Although Eisenhower warned Kennedy about Laos and Vietnam, Europe and Latin America "loomed larger than Asia on his sights." In June 1961, he bitterly disagreed with Soviet premier Nikita Khrushchev when they met in Vienna to discuss key U.S.–Soviet issues. Only 16 months later,

5300-422: The bore diameter and the length of the cartridge case; for example, the 6.5×55mm Swedish cartridge has a bore diameter of 6.5 mm and a case length of 55 mm. The means of measuring a rifled bore varies, and may refer to the diameter of the lands or the grooves of the rifling. For example, the 257 Roberts and 250 Savage both use a .257 inch projectile; both 250 Savage and 257 Roberts rifle bores have

5400-545: The bullet weight in grains was designated, such as 45-70-405. This scheme was far more popular and was carried over after the advent of early smokeless powder cartridges such as the 30-30 Winchester and 22 Long . Later developments used terms to indicate relative power, such as .44 Special and .44 Magnum . Variations on these methods persist today, with new cartridges such as the 204 Ruger and 17 HMR (Hornady Magnum Rimfire). Metric diameters for small arms refer to cartridge dimensions and are expressed with an "×" between

5500-422: The calculated 20 ft/s (6.1 m/s). The testers suggested that the (secret) manufacturing process was designed to achieve this effect. However, independent analysis of those testers' own published data shows that their conclusions were incorrectly calculated. The projectile's acceleration actually started out low and continually increased over the bullet's measured flight. Aside from a few Gyrojets tested by

5600-491: The combustion considerably less reliable. The ports themselves could also become fouled fairly easily, although it was suggested that this could be solved by sealing the magazines or ports. Versions of the Gyrojet that were tested were inaccurate, cumbersome, slow loading, and unreliable. At best, a 1% failure rate was suggested; users quote worse figures, with many rounds that misfired the first time but later fired. Possibly these disadvantages could have been overcome in time, but

5700-451: The contemporary English ( avoirdupois ) pound massed of approximately 454 g (1.001 lb). Thus, a French 32-pounder at the Battle of Trafalgar threw a shot with 1.138 kg (2.51 lb) more mass than an English 32-pounder. Complicating matters further, muzzle-loaded weapons require a significant gap between the sides of the tube bore and the surface of the shot. This is necessary so

5800-495: The country . Tensions between the Viet Minh and French authorities had erupted into full-scale war by 1946, a conflict which soon became entwined with the wider Cold War . On March 12, 1947, US President Harry S. Truman announced the Truman Doctrine , an anticommunist foreign policy which pledged US support to nations resisting "attempted subjugation by armed minorities or by outside pressures". In Indochina, this doctrine

5900-491: The country to the Virgin Mary . In the summer of 1955, Diệm launched the "Denounce the Communists" campaign, during which suspected communists and other anti-government elements were arrested, imprisoned, tortured, or executed. He instituted the death penalty in August 1956 against activity deemed communist. The North Vietnamese government claimed that, by November 1957, over 65,000 individuals were imprisoned and 2,148 killed in

6000-618: The demilitarized zone, between North and South Vietnam. The North Vietnamese Communist Party approved a "people's war" on the South at a session in January 1959, and, in May, Group 559 was established to maintain and upgrade the Ho Chi Minh trail , at this time a six-month mountain trek through Laos. On 28 July, North Vietnamese and Pathet Lao forces invaded Laos, fighting the Royal Lao Army all along

6100-531: The early established cartridge arms was the Spencer repeating rifle , which Union forces used in the American Civil War . It was named based on the chamber dimensions, rather than the bore diameter, with the earliest cartridge called the "No. 56 cartridge", indicating a chamber diameter of .56 in; the bore diameter varied considerably, from .52 to .54 in. Later various derivatives were created using

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6200-470: The end of 1965, and to 536,000 by the end of 1968. US forces relied on air supremacy and overwhelming firepower to conduct search and destroy operations in rural areas. In 1968, North Vietnam launched the Tet Offensive , which was a tactical defeat but convinced many in the US that the war could not be won. The PAVN began engaging in more conventional warfare . Johnson's successor, Richard Nixon , began

6300-432: The end of their barrel life, whereby the rifling is worn down to a point where a rifle loses some of its accuracy , the choice to make a caliber or cartridge change is often done at the same time as when a new rifle barrel is fitted to the rifle by a gunsmith . There are a few important factors to consider when converting a rifle to a different caliber or cartridge. The action of the rifle should be long enough to contain

6400-458: The gyrojet flare, the A/P25S-5A came with a bandolier of seven flares and had an effective altitude of over 1,500 feet (460 metres). Its rounded-nose projectile was designed to ricochet through trees and clear an over canopy of branches. An underwater firearm variant of the Gyrojet called the "Lancejet" was considered for use by the United States military. It was planned and tested but not adopted;

6500-452: The inaccuracy of the weapon eventually removed it from consideration. An experimental twelve-barrel Gyrojet pepperbox -type pistol was planned to be used, but was not, in the film version of You Only Live Twice . The Studies and Observations Group (SOG) of the U.S. military in Vietnam in 1967 saw an opportunity to try out one of the SOG's new developments, a revolutionary rocket pistol called

6600-711: The insurgency entitled "The Road to the South" to the Politburo in Hanoi. However, as China and the Soviets opposed confrontation, his plan was rejected. Despite this, the North Vietnamese leadership approved tentative measures to revive southern insurgency in December 1956. Communist forces were under a single command structure set up in 1958. In May 1958, North Vietnamese forces seized the transportation hub at Tchepone in Southern Laos near

6700-402: The landlords back, people who had been farming land for years had to return it to landlords and pay years of back rent. Marilyn B. Young wrote that "The divisions within villages reproduced those that had existed against the French: 75% support for the NLF, 20% trying to remain neutral and 5% firmly pro-government". In March 1956, southern communist leader Lê Duẩn presented a plan to revive

6800-416: The larger Indochina refugee crisis , which saw millions leave Indochina, an estimated 250,000 perished at sea. The US destroyed 20% of South Vietnam's jungle and 20–50% of the mangrove forests, by spraying over 20 million U.S. gallons (75 million liters) of toxic herbicides; a notable example of ecocide . The Khmer Rouge carried out the Cambodian genocide , while conflict between them and

6900-421: The length of the barrel, with the use of chokes and back-boring. In the United Kingdom, "gauge" is referred to as "bore" and in the United States "bore" is referred to as "gauge", e.g. a "12-bore shotgun or 12-gauge shotgun" has a bore or gauge that can accommodate a lead sphere weighing 1/12th of a pound. The term caliber is used as a measure of length of artillery barrels from muzzle to breech, expressed as

7000-420: The long run, adverse military consequences." The quality of the South Vietnamese military, however, remained poor. Poor leadership, corruption, and political promotions weakened the ARVN. The frequency of guerrilla attacks rose as the insurgency gathered steam. While Hanoi's support for the VC played a role, South Vietnamese governmental incompetence was at the core of the crisis. One major issue Kennedy raised

7100-458: The maximum velocity varied from slightly below to slightly above Mach 1. In 1965, the manufacturer of the pistol claimed 5-mil accuracy (about 17 MOA, or about 4.5 inches at 25 yards), worse than conventional pistols of the time. However, in later tests accuracy was very poor; the difference seems to have been due to a manufacturing flaw in later production runs which partially blocked one of the exhaust ports, creating asymmetrical thrust that caused

7200-402: The most common sizes encountered, although larger, smaller and intermediate sizes existed. In practice, though, significant variation occurred in the actual mass of the projectile for a given nominal shot weight. The country of manufacture is a significant consideration when determining bore diameters. For example, the French livre , until 1812, had a mass of 489.5 g (1.079 lb), whilst

7300-426: The new cartridge, the magazine should also be able to hold the new cartridge, the bolt face should be the correct diameter and the extractor the correct size to hold the head of the new cartridge. The most common of these caliber conversions on rifles, are usually done to change from a parent cartridge to a new cartridge based on it, like when converting a rifle to a 6.5 mm Creedmoor from a 308 Winchester on which it

7400-446: The other communists and anti-GVN activists. Douglas Pike estimated that insurgents carried out 2,000 abductions, and 1,700 assassinations of government officials, village chiefs, hospital workers and teachers from 1957 to 1960. Violence between insurgents and government forces increased drastically from 180 clashes in January 1960, to 545 clashes in September. In September 1960, COSVN , North Vietnam's southern headquarters, ordered

7500-633: The pro-Western government of Laos and the Pathet Lao communist movement in May, construction of the Berlin Wall in August, and the Cuban Missile Crisis in October. Kennedy believed another failure to stop communist expansion would irreparably damage US credibility. He was determined to "draw a line in the sand" and prevent a communist victory in Vietnam. He told James Reston of The New York Times after

7600-412: The process. According to Gabriel Kolko , 40,000 political prisoners had been jailed by the end of 1958. In October 1956, Diệm launched a land reform program limiting the size of rice farms per owner. 1.8m acres of farm land became available for purchase by landless people. By 1960, the process had stalled because many of Diem's biggest supporters were large landowners. In May 1957, Diệm undertook

7700-405: The projectile may be inserted from the mouth to the base of the tube and seated securely adjacent the propellant charge with relative ease. The gap, called windage , increases the size of the bore with respect to the diameter of the shot somewhere between 10% and 20% depending upon the year the tube was cast and the foundry responsible. The relationship between bore diameter and projectile weight

7800-434: The projectile through a rifled barrel. Combustion gases released within the barrel were vented through vent holes in it. Spin stabilization is limited in accuracy as a targeting technique by the accuracy with which one can point the launching tube and the accuracy with which the orientation of the projectile is constrained by the tube. The technique requires the shooter to have a line of sight to their target. The rocket leaves

7900-617: The projectile to corkscrew through the air. About 1000 of the "Rocketeer" model pistols were produced; a few saw service in the Vietnam War , and were featured in the James Bond book and movie You Only Live Twice , the Matt Helm film Murderers' Row , as well as one of The Man from U.N.C.L.E. novels, The Monster Wheel Affair . At about the same general size as the Colt M1911, the Gyrojet

8000-402: The rough bore, leaving the "lands" behind. Good performance requires a concentric, straight bore that accurately centers the projectile within the barrel, in preference to a "tight" fit which can be achieved even with off-center, crooked bores that cause excessive friction, fouling and an out-of-balance, wobbling projectile in flight. Calibers fall into four general categories by size: There

8100-567: The same basic cartridge, but with smaller-diameter bullets; these were named by the cartridge diameter at the base and mouth. The original No. 56 became the .56-56, and the smaller versions, .56-52, .56-50, and .56-46. The 56–52, the most common of the new calibers, used a 50-cal bullet. Other black powder-era cartridges used naming schemes that appeared similar, but measured entirely different characteristics; 45-70 , 44-40 , and 32-20 were designated by bullet diameter to hundredths of an inch and standard black powder charge in grains . Optionally,

8200-504: The same bore diameter, often involves merely re-chambering the barrel to the new cartridge dimensions, if the rim diameter of the new cartridge matches that of the old cartridge. Converting a rifle to fire a different cartridge in a different caliber and bore as what it initially was, means that the barrel of the rifle will also need to be changed. Because many competitive precision rifle shooters often shoot thousands of rounds per year both for practice and competitions, and they more often reach

8300-769: The supervision of "local commissions". The US countered with what became known as the "American Plan", with the support of South Vietnam and the UK. It provided for unification elections under the supervision of the UN, but was rejected by the Soviet delegation. The US said, "With respect to the statement made by the representative of the State of Vietnam, the United States reiterates its traditional position that peoples are entitled to determine their own future and that it will not join in any arrangement which would hinder this". US President Eisenhower wrote in 1954: I have never talked or corresponded with

8400-544: The technology did not offer enough advantages over conventional small arms to survive. The original designer Robert Mainhardt enlisted the help of his friend Nick Minchakievich of Pleasanton, California , before 1962, in helping to stabilize the projectiles or ammunition. Minchakievich first developed retractable fins after rear ignition proved too dangerous. But the retractable fins proved too expensive, requiring advanced machining during production. The two experimental calibers with retractable fins were 6mm and 13mm. Rushed for

8500-405: The twentieth century. The inherent difference between a conventional firearm and a rocket is that the projectile of a conventional firearm builds up to its maximum speed in the barrel of the firearm, then slows down over its trajectory; the rocket continues to accelerate as long as the fuel burns, then continues its flight like an un-powered bullet. A bullet has maximum kinetic energy at the muzzle;

8600-511: The two provisional states for a 300-day period. Elections throughout the country were to be held in 1956 to establish a unified government. However, the US, represented at the conference by Secretary of State John Foster Dulles , objected to the resolution; Dulles' objection was supported only by the representative of Bảo Đại. John Foster's brother, Allen Dulles , who was director of the Central Intelligence Agency , then initiated

8700-587: The unified Vietnam escalated into the Cambodian–Vietnamese War . In response, China invaded Vietnam , with border conflicts lasting until 1991. Within the US, the war gave rise to Vietnam syndrome , a public aversion to American overseas military involvement, which, with the Watergate scandal , contributed to the crisis of confidence that affected America throughout the 1970s. Various names have been applied and have shifted over time, though Vietnam War

8800-522: Was an armed conflict in Vietnam , Laos , and Cambodia fought between North Vietnam (Democratic Republic of Vietnam) and South Vietnam (Republic of Vietnam) and their allies. North Vietnam was supported by the Soviet Union and China , while South Vietnam was supported by the United States and other anti-communist nations. The conflict was the second of the Indochina Wars and a major proxy war of

8900-430: Was considerably lighter at only 22 ounces (625 g), as the structure was mostly made of Zamac , a zinc alloy. The weapon was cocked by sliding forward a lever above the trigger to pull a round into the gun; the lever sprang back when the trigger was pulled. The lever hit the bullet on the nose, driving it into the firing pin. As the round left the chamber, it pushed the lever forward again to recock it. The pistol lacked

9000-462: Was considered a destructive device and required paying a tax and obtaining a license. The registration process was changed several years later, but in the interim, MBA created the legal Gyrojet Mark II, firing a .49 caliber rocket. Assault rifle variant with M16-type ergonomics tested by the US Army. This variant had full auto capability and a removable grip inserted magazine. To increase ammo capacity, it

9100-451: Was defeated in April following a battle in Saigon . As broad-based opposition to his harsh tactics mounted, Diệm increasingly sought to blame the communists. In a referendum on the future of the State of Vietnam in October 1955, Diệm rigged the poll supervised by his brother Ngô Đình Nhu and was credited with 98% of the vote, including 133% in Saigon. His American advisors had recommended

9200-505: Was designed, including the pistol , the carbine and a rifle , as well as a proposed squad-level light machine gun and a needlegun known as the Lancejet; however only the pistol and carbine were built. The space age -looking carbines and an assault rifle variant with a removable grip-inserted magazine were tested by the US Army, where they proved to have problems. One issue was that the vent ports allowed humid air into fuel, where it made

9300-433: Was divided into two parts at the 17th parallel : the Viet Minh , led by Ho Chi Minh , took control of North Vietnam, while the US assumed financial and military support for South Vietnam, led by Ngo Dinh Diem . The North Vietnamese began supplying and directing the Viet Cong (VC), a common front of dissidents in the south, which intensified a guerrilla war from 1957. In 1958, North Vietnam invaded Laos , establishing

9400-863: Was first proposed by the Eisenhower administration . John F. Kennedy , then a senator , said in a speech to the American Friends of Vietnam : "Burma, Thailand, India, Japan, the Philippines and obviously Laos and Cambodia are among those whose security would be threatened if the Red Tide of Communism overflowed into Vietnam." A devout Roman Catholic, Diệm was fervently anti-communist, nationalist, and socially conservative. Historian Luu Doan Huynh notes "Diệm represented narrow and extremist nationalism coupled with autocracy and nepotism ." Most Vietnamese were Buddhist , and alarmed by Diệm's actions, like his dedication of

9500-656: Was first put into practice in February 1950, when the United States recognized the French-backed State of Vietnam in Saigon , led by former Emperor Bảo Đại, as the legitimate government of Vietnam, after the communist states of the Soviet Union and People's Republic of China recognized the Democratic Republic of Vietnam , led by Ho Chi Minh, as the legitimate Vietnamese government the previous month. The outbreak of

9600-468: Was killed in a US-backed military coup , which added to the south's instability. Following the Gulf of Tonkin incident in 1964, the US Congress passed a resolution that gave President Lyndon B. Johnson authority to increase military presence without a declaration of war. Johnson launched a bombing campaign of the north and began sending combat troops, dramatically increasing deployment to 184,000 by

9700-464: Was mainly in the Red River Delta area, 50,000 executions became accepted by scholars. However, declassified documents from Vietnamese and Hungarian archives indicate executions were much lower, though likely greater than 13,500. In 1956, leaders in Hanoi admitted to "excesses" in implementing this program and restored much of the land to the original owners. The south, meanwhile, constituted

9800-1072: Was severed following the widespread adoption of rifled weapons during the latter part of the 19th century. Guns continued to be classed by projectile weight into the mid-20th century, particularly in British service with guns, such as the 2-pounder , 6-pounder , and 17-pounder anti-tank weapons . However, this value no longer definitively related to bore diameter, since projectiles were no longer simple spheres—and in any case were more often hollow shells filled with explosives rather than solid iron shot. Vietnam War ≈860,000 (1967) ≈1,420,000 (1968) Total military dead/missing: ≈1,100,000 Total military wounded: ≈604,200 (excluding GRUNK / Khmer Rouge and Pathet Lao ) Second Third American intervention 1965 1966 1967 Tet Offensive and aftermath Vietnamization 1969–1971 1972 Post- Paris Peace Accords (1973–1974) Spring 1975 Air operations Naval operations Lists of allied operations The Vietnam War (1 November 1955 – 30 April 1975)

9900-444: Was usually expressed as the weight of its iron shot in pounds . Iron shot was used as the standard reference because iron was the most common material used for artillery ammunition during that period, and solid spherical shot the most common form encountered. Artillery was classified thereby into standard categories, with the 3-pounder, 4-pounder, 6-pounder, 8-pounder, 9-pounder, 12-pounder, 18-pounder, 24-pounder, and 32-pounder being

10000-518: Was whether the Soviet space and missile programs had surpassed those of the US. Although Kennedy stressed long-range missile parity with the Soviets, he was interested in using special forces for counterinsurgency warfare in Third World countries threatened by communist insurgencies. Although they were intended for use behind front lines after a conventional Soviet invasion of Europe, Kennedy believed guerrilla tactics employed by special forces, such as

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