6mm Lee Navy

Type

Rifle

Place of origin

USA

Production history

Designed

1895

Specifications

Case type

Semi-rimmed, bottleneck

Bullet diameter

0.244 (0.236 dia. before rifling)

Neck diameter

.278 in (7.1 mm)

Shoulder diameter

.402 in (10.2 mm)

Base diameter

.445 in (11.3 mm)

Rim diameter

.448 in (11.4 mm)

Case length

2.35 in (60 mm)

Overall length

3.11 in (79 mm)

Rifling twist

1:7½

Primer type

Boxer large rifle

Ballistic performance

Bullet mass/type	Velocity	Energy
75 gr (5 g)	3,300 ft/s (1,000 m/s)	1,809 ft·lbf (2,453 J)
100 gr (6 g)	2,680 ft/s (820 m/s)	1,595 ft·lbf (2,163 J)
112 gr (7 g)	2,650 ft/s (810 m/s)	1,895 ft·lbf (2,569 J)
112gr (7.3g) (military loading)	2,560 ft/s (780 m/s)	1,629 ft·lbf (2,209 J)

Test barrel length: 24 in.; 28 in. (M1895)
Source(s): Barnes & Amber; Sharpe, Philip, The Rifle in America

The 6mm Lee Navy (6×60mmSR), also known as the 6mm U.S.N. or .236 Navy, is an obsolete American rifle cartridge. It was the service cartridge of the United States Navy and Marine Corps from 1895, officially replacing the .45-70 Government round, and was the first small-bore high-velocity smokeless powder cartridge to be adopted by either service. The 6mm Lee Navy was in turn replaced by the .30 Army (.30-40 Krag) cartridge in 1899.

By 1894, the U.S. Navy desired to adopt a modern small-bore, smokeless powder service cartridge and rifle in keeping with other first-line naval powers for both naval and marine forces. Naval authorities decided that the new cartridge should be adaptable to both rifles and machine guns. Noting that the world's military forces were adopting smaller and smaller caliber rifles with higher velocity cartridges, U.S. naval authorities decided to leapfrog the trend to smaller and smaller calibers by adopting a cartridge in 6 mm (0.236 inch) caliber, with a semi-rimmed case capable of holding up to 40 gr (0.091 oz; 2.6 g) of 'rifleite' smokeless powder and proof chamber pressures of up to 60,000 psi. While the government cartridge was being developed, the Navy tested rifle barrels in various alloys and rifling twists, eventually settling on a barrel steel made of 4.5 percent nickel steel, with a rifling twist of one turn in 6.5 inches.

As the Chief of the Bureau of Naval Ordnance stated in his 1897 Small Arms report to the Secretary of the Navy, "In making what may appear a radical departure in its selection of a caliber smaller than as yet adopted elsewhere...the Bureau is convinced it is looking to the future … it is surely wise to attempt to advance with one stride as far as existing conditions allow toward the goal to which the world is moving with slow steps." The report went on to list the advantages of the smaller 6 mm caliber: greatly increased velocity, flatness of bullet trajectory, reduced recoil, a 100% increase in penetration compared to the former .45-70 Government cartridge, and the ability to carry twice the number of cartridges per individual sailor or marine. The report acknowledged, however, that the 6 mm round had two principal disadvantages: first, as a small-caliber round, the 6 mm bullet would not sufficiently wound an enemy to put him out of action, and second, the "shock" or stopping power of the smaller bullet would not "stop the onset of excited men at short range." In answer to these objections, the report gave three responses: first, "the battle of the future will be fought at long range, and men will not live to come to close quarters with an enemy who stands his ground"; second, "99 percent of wounded enemy soldiers were unlikely to investigate the severity of their wound, but simply retire to the rear", and last, "the explosive effect of a small-caliber, high-velocity bullet against the human body—the bullet tumbles or fragments to produce devastating wounds against bone or fluid-filled organs—would be more incapacitating at all ranges than wounds made by a slow-moving bullet of large caliber.

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Wikipedia