JM61 (20 mm)

Description

The 20 mm JM61 is a Japanese naval cannon. It is a version of the 20 mm JM61A1 rotary aircraft cannon equipped on Japanese jet fighters.

Vehicles equipped with this weapon

PG 02

General info

The JM61 has the second-highest rate of fire of any naval weapon, at a whopping 3,000 rounds per minute (RPM). As such, the JM61 can shred through any boat with ease and even dissect larger ships. There is also a modification available to lower the rate of fire to 450 RPM, but the decrease in effectiveness is not worth the extra time of continuous fire.

Available ammunition

The JM61 has a choice of 3 belts: HEI, API-T, and APDS.

20 mm HEI belts: HEF-I · API-T · HEF-I · HEF-I · API-T · HEF-I
API-T: API-T · HEF-I · API-T · API-T · HEF-I · API-T
20 mm APDS belts: APDS · APDS · APDS · APDS

Penetration statistics
Ammunition	Penetration @ 0° Angle of Attack (mm)
Ammunition	10 m	100 m	500 m	1,000 m	1,500 m	2,000 m
API-T	40	36	22	12	6	3
HEF-I	2	2	2	2	2	2
APDS	64	62	53	44	37	30

Shell details
Ammunition	Velocity (m/s)	Projectile mass (kg)	Fuse delay (m)	Fuse sensitivity (mm)	Explosive mass (TNT equivalent) (g)	Ricochet
Ammunition	Velocity (m/s)	Projectile mass (kg)	Fuse delay (m)	Fuse sensitivity (mm)	Explosive mass (TNT equivalent) (g)	0%	50%	100%
API-T	1,030	0.1	-	-	-	47°	60°	65°
HEF-I	1,030	0.1	0	0.1	17.12	79°	80°	81°
APDS	1,128	0.07	-	-	-	75°	78°	80°

Comparison with analogues

AK-230 - 30 mm CIWS cannon found on the Pr. 206, has a third the rate of fire, but each turret has 2 barrels, meaning that the Pr. 206 effectively fires 4,000 RPM
30 mm/54 AK-630 - 30 mm CIWS cannon mounted on the MPK Pr.12412, has an even higher rate of fire than the JM61 at 5,000 RPM, but no access to any armour-piercing rounds

Usage in battles

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Pros and cons

Pros:

Very high rate of fire
API-T and APDS belts can cut through most ships it meets

Cons:

Overheats quickly, continuous fire is not recommended

History

With Japan's industry badly damaged by World War II and only just exiting a stage of economic recovery at the time, the Japanese Maritime Self-Defense Force's (JMSDF) first ships were transfers from the US Navy. Even when the JMSDF began building their ships in 1956, they still used American designed weapons such as the 3 inch Mk.33 to arm them. The practice continues to the present with the entirety of Japan's naval weapons being based on American designs or from other foreign nations such as Italy.

The JM61 is another example of their use of American designs. A licensed version of the M61 Vulcan adopted by the United States Air Force in 1959 for fighter aircraft, the cannon would be used in other applications. In the 1970s, the United States Navy used the Vulcan as the basis for the Phalanx Close-In Weapon System (CIWS) as a last line of defense against attacks against their ships. Entering service in 1980, the design was adopted by a number of America's allies including Japan. Around 1990, the JM61 seen in-game was developed. Based on the CIWS, it used a simplified mounting that was less complex and developed by Sumitomo Heavy Industries Ltd. While the Phalanx was the weapon of choice for JMSDF destroyers, the JM61 in its numerous variants is the weapon used for smaller vessels such as minesweepers, landing craft and patrol boats such as PG 02. The gun is also by the Maritime Security Agency (now the Japanese Coast Guard) starting FY1979 to replace their aging 20 mm/70 Oerlikon guns from World War II.

Media

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External links

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topic on the official game forum;
other literature.

Japan naval cannons
20 mm	JM61 · Type 98
25 mm	25 mm/60 Type 96
37 mm	Type 4 · Type 11 pattern 1922
40 mm	40 mm/62 Vickers
57 mm	Type 97
75 mm	Type 88 AA
76 mm	3-inch/40 Type 41 · 8 cm/40 3rd Year Type · 8 cm/60 Type 98
100 mm	100/65 mm Type 98 mod A
120 mm	120 mm/45 3rd Year Type · 120 mm/45 10th year type
127 mm	5 inch/40 Type 89 · 127 mm/50 3rd Year Type
140 mm	140 mm/50 3rd Year Type
152 mm	6-inch/45 Type 41 · 15 cm/50 Type 41
155 mm	155 mm/60 3rd Year Type
200 mm	20 cm 3rd year type No.1
203 mm	20 cm/45 Type 41 · 20 cm/50 3rd year type No.2
356 mm	36 cm/45 Type 41
410 mm	410 mm/45 Type 3
	Foreign:
20 mm	20 mm/70 Oerlikon Mk.II ^{(USA/Britain)}
40 mm	Bofors L/60 Mark 1 ^(USA) · Bofors L/60 Mark 2 ^(USA) · Bofors L/60 Mark 3 ^(USA)
47 mm	3 pdr QF Hotchkiss ^(Britain)
76 mm	3-inch Mark 10 ^(USA) · 3 inch Mk.33 ^(USA) · 3-inch Mk.34 ^(USA)
120 mm	4,7-inch/40 Armstrong ^(Britain)
127 mm	5 inch/38 Mk.12 ^(USA)
305 mm	12-inch/45 Vickers ^(Britain) · 12-inch/50 Vickers ^(Britain)