7×20mm Nambu

The 7×20mm Nambu is a rimless, bottleneck handgun cartridge designed in Japan for use in the Type B or "Baby" model Nambu pistol.[1] The cartridge is a scaled-down version of the 8×22mm Nambu used in all other Nambu pistol models. It has a muzzle energy more than a .25 ACP and close to the .32 ACP.[2][3][4]

7×20mm Nambu
Type	Pistol
Place of origin	Japan
Service history
In service	1903-1945
Used by	Japan
Wars	World War II
Production history
Designer	Kijiro Nambu
Designed	1902
Manufacturer	Type B Nambu Pistol 1. Tokyo Artillery Arsenal, Koishigawa, Tokyo 1903-1923 and 2. Tokyo Gas and Electric Co., Ltd., Tokyo 1923-1929. Was ammunition made in the same factories?
No. built	Pistols - Possibly less than 6,500. 1. Tokyo c. 5,900 and 2. TGE c. 550. Number of 7x20mm rounds made is unknown but today they are a quite rare collector's item occasionally found in WW2 boxes of 50 rounds.
Variants	At least 5, including a dummy. Variations mainly occur in type of bullet crimping, jacket type and rim thickness.
Specifications
Case type	Bottleneck rimless
Bullet diameter	7.08 mm (0.279 in)
Neck diameter	7.64 mm (0.301 in)
Shoulder diameter	8.62 mm (0.339 in)
Base diameter	8.91 mm (0.351 in)
Rim diameter	9.11 mm (0.359 in)
Rim thickness	0.98 mm (0.039 in)
Case length	19.80 mm (0.780 in)
Overall length	26.80 mm (1.055 in)
Primer type	Small pistol
Ballistic performance
Bullet mass/type Velocity Energy 56 gr (4 g) FMJ 240 m/s (790 ft/s) 108 J (80 ft⋅lbf)
Test barrel length: 83 mm (3.25 in)

References

1. Miller, David (2007). Fighting Men of World War II, Volume I: Axis Forces—Uniforms, Equipment, and Weapons. Stackpole Books. p. 276. ISBN 0-8117-0277-4.
2. "An Introduction to the Military Handguns of Imperial Japan". Gun Digest 2010. Krause Publications. 2009.
3. Dave Maccar (2016). Handguns & Handgun Shooting. p. 88. ISBN 1440246106.
4. T J Mullin (2015). 365 Guns You Must Shoot: The Most Sublime, Weird, and Outrageous Guns Ever. p. 167.

the Hand Cannons of Imperial Japan, Derby,H., 1981, Taylor Publishing Company, ISBN 0-940424-00-2 The Weapons Series no. 5 THE BABY NAMBU Japanese 7-mm. Pistol. Marsh, Roger, 1946, Pub. by the author.