20mm Vulcan

     Notes:  The Vulcan, and its upgraded version, the PIVAD, is one of the most common air defense guns in the world, whether in trailer-mounted versions, fixed mountings, naval mountings, and vehicular use.  A modified form is a very common aircraft gun.  The Vulcan is a six-barreled rotary cannon that fires at an extremely rapid rate of fire, projecting a virtual wall of metal at targets. 

     The Vulcan has also been used as armament for most US military and US-made military aircraft since the 1950s; in fact, the Vulcan was first designed for use on the F-104 Shooting Star interceptor.  In this guise, the Vulcan has the designation M61.  The initial design, the M61, was fed by linked ammunition, and sent out for testing in the then-new F-104.  The M61, which had been plagued by misfeeds and jams up to this point, ejected itís expended links overboard through a slot under the fighter.  The test pilot, firing while in a turn at about Mach 2, found that the expended links were ingested into itís air intake on the right side and also hit the wing, which was a carefully-shaped special airfoil, and the links hitting the wing munged up the aerodynamics.  The test pilot, therefore, got to be the first pilot to find out what itís like to eject from an aircraft at Mach 2 speeds.  (He spent months in the hospital, and months more before he was fit enough for flying status.)

     The M61A1 did away with the linked ammunition feed in favor of linkless feed.  This essentially worked miracles, making jams rare and doing away with any problems caused by spent links being ejected overboard.  In addition, expended cases are retained inside the aircraft to keep them from doing the same thing the M61ís expended links did.  The M61A1 became the standard aircraft cannon for almost all US and US-made aircraft for 50-odd years, and it is still in widespread use.  It inspired virtually all rotary cannons and machineguns which were designed after the Vulcan.  The nominal rate of fire for the M61A1 is 6000 rounds per minute (though not even the AC-130s that carry the Vulcan have that much ammunition); pilots normally fire in one-second of half-second burst, firing 100 or 50 rounds at an attack.  Some M61A1s (such as on the Brazilian/Italian AMX and the F-106 Delta Dart) have their rate of fire throttled to 4000 rounds per minute, and some attack aircraft (like the A-7 Corsair II) can have a rate of fire selected by the pilot at either 4000 or 6000 rounds per minute.

     The M61A1 can also be mounted under an aircraft (on the wings or centerline; in practice, the pods are not mounted on the wing except in those rare instances that a pod is carried under each wing); this pod is known as the GAU-4.  Early versions of this pod were powered by ram air provided by the forward motion of the aircraft; however, it was quickly discovered in Vietnam that the GAU-4 became unreliable when the aircraft carrying it was traveling at less than 400 kmh.  The GAU-4 was modified into the GAU-4/A, which is powered by electricity from a small generator inside the pod..

     There is a new version of the M61, the M61A2; this version is made of lighter materials, including a lot of titanium and even ceramics and composites. In addition, the designers literally removed any metal that did not directly contribute to the operation of the gun, and the electrical power unit was able to be made lighter due to new technology.  The M61A2 was originally designed for the F-22 Raptor, but it is now also found on the F/A-18E/F Super Hornet and F-15EX Eagle II.

     Aircraft equipped with the Vulcan normally use API ammunition.

     The US Army calls the M61A1 the M130; itís primary use in the Army is on the M167 VADS towed SPAAG, and the M163 VADS.  The M163 is mounted on a modified M113 APC chassis; the M167 is on a towed mount and is normally towed by a medium truck which also carries more 20mm Vulcan ammunition.  The M167 trailer also carries a 10kW generator to power the M130. Initially, the generator was powered by a large diesel fuel tank, but the fuel used was later changed in US Army service to JP8. The generator and the fuel tank essentially form the gunnerís platform, and the rest of the VADS is on top of this.

     The M130 gun is also mounted on the Israeli Machbet, a variant of the M163, and the original Phalanx CIWS naval weapons. It is also mounted on an Army AAA version of the Phalanx; this mount is still in advanced development, but combat testing in Iraq and Saudi Arabia have yielded good results against cruise missiles, rockets, and UAV.  Sudan and Yemen use M167 Vulcans mounted on top of BTR-152s, and a modified M167 mount has been seen mounted in the back of a Toyota Land Cruiser in Yemen in the hands of the Houthi.

     The standard VADS system, whether an M167 or M163, has a range-only radar and an optical lead-calculating sight.  The M167A2 PIVAD adds a new digital optical sight and a ballistic computer, and is much more accurate than the VADS system on the M167 VADS.  (These improvements were also made to the M163.)  The M130 gun on the VADS and PIVAD may be programmed by the gunner to fire in 10, 30, 60, or 100-round bursts, though the nominal rate of fire is 3000 rounds per minute.  The size of bursts is programmed by the gunner.  VADS and PIVAD systems normally use HEI-T rounds (an HEI round with a tracer base).  A use not often mentioned for the M167 and M163 is itís ability to depress the gun enough to be used against ground targets; they can decimate infantry, shred light vehicles, and even take out some light armored vehicles.

     Though the M167, and in some cases, the M163, are still used worldwide, the VADS and PIVAD systems were phased out in the US in favor of the M1097 Avenger SAM system and will also be replaced by the truck-mounted Phalanx CIWS.  The M6 Bradley Linebacker was also to be a replacement for the M163, though the M6 itself was phased out by the Army after a few years. (I donít know what brilliant General or Congressional Committee made that decision, or what they were thinking when he decided to shelve the LinebackerÖ)

     A third model, the Basic Vulcan, is an M167 designed for export to poorer countries; it deletes the radar, digital sight, and power controls for elevation and traverse.

     The Basic Vulcan, VADS, and PIVAD are grouped in the second table below by the gun used (the M130 Vulcan).  Note that the range of the M130 Vulcan differs from the M61; this is because the M130 uses longer barrels.

 

Weapon

Ammunition

Crew

Set Up Time

Weight

Price

M61A1

20mm Vulcan

Depends on Aircraft

N/A

112 kg

$55421

M61A2

20mm Vulcan

Depends on Aircraft

N/A

92 kg

$60964

Basic Vulcan

20mm Vulcan

3

4 Minutes

1565 kg

$32769

Vulcan ADA

20mm Vulcan

4

4 Minutes

1588 kg

$43692

PIVAD

20mm Vulcan

4

4 Minutes

1732 kg

$53692

 

Weapon

ROF

Magazine

Range

Round

Damage

Penetration

M61A1 Vulcan

500

Depends on Aircraft Capacity

420

AP

4

2/2/2/1

 

500

Depends on Aircraft Capacity

420

APDS

4

4/3/3/2

500

Depends on Aircraft Capacity

420

API

4

3/3/2/1

 

500

Depends on Aircraft Capacity

300

HEI

C1  B5

-4C

 

500

Depends on Aircraft Capacity

420

MPT-SD

4

4/3/3/2

 

500

Depends on Aircraft Capacity

300

SAPHEI

C1  B3

2/2/2/1

M61A1 Vulcan (4000 RPM)

333

Depends on Aircraft Capacity

420

AP

4

2/2/2/1

 

333

Depends on Aircraft Capacity

420

APDS

4

4/3/3/2

 

333

Depends on Aircraft Capacity

420

API

4

3/3/2/1

 

333

Depends on Aircraft Capacity

300

HEI

C1  B5

-4C

 

333

Depends on Aircraft Capacity

420

MPT-SD

4

4/3/3/2

 

333

Depends on Aircraft Capacity

300

SAPHEI

C1  B3

2/2/2/1

M61A2 Vulcan

550

Depends on Aircraft Capacity

420

AP

4

2/2/2/1

 

550

Depends on Aircraft Capacity

420

APDS

4

4/3/3/2

 

550

Depends on Aircraft Capacity

420

API

4

3/3/2/1

 

550

Depends on Aircraft Capacity

300

HEI

C1  B5

-4C

 

550

Depends on Aircraft Capacity

420

MPT-SD

4

4/3/3/2

 

550

Depends on Aircraft Capacity

300

SAPHEI

C1  B3

2/2/2/1

M130 Vulcan

250

300 Chute, 500 Chute

490

AP

4

2/2/2/1

 

250

300 Chute, 500 Chute

490

APDS

4

4/3/3/2

 

250

300 Chute, 500 Chute

490

API

4

3/3/2/1

 

250

300 Chute, 500 Chute

370

HEI

C1  B5

-4C

 

250

300 Chute, 500 Chute

490

MPT-SD

4

4/3/3/2

 

250

300 Chute, 500 Chute

370

SAPHEI

C1  B3

2/2/2/1

 

25mm M-242 Chain Gun

     Notes:  Also known as the Bushmaster, this autocannon is fitted to the M-2 and M-3 Bradley Fighting Vehicles and the LAV-25, as well as US Navy deck mountings.  It is also employed on MOWAG Piranhas used by the Saudis.  Rounds may be fired on semiautomatic, ROF 2, ROF3, or ROF5.  This weapon fires both US-made and European ammunition.  The mechanism is actuated by a chain drive, hence the name. It is noteworthy that before Operation Iraqi Freedom, the US Army was heavily considering replacing the Bradleyís 25mm M-242 with a heavier-caliber autocannon; however, the 25mm M-242 has outperformed expectations and its replacement is no longer being considered.

Weapon

Ammunition

Crew

Set Up Time

Weight

Price

M-242

25mm KBA

1

NA

153.5 kg

$11270

 

Weapon

ROF

Magazine

Range

Round

Damage

Penetration

M-242 ChainGun

5

100B (x2)

390

AA

C1  B8

-4C

 

5

100B (x2)

520

APFSDSDU

6

14/12/10/7

 

5

100B (x2)

520

API

6

5/4/3/2

 

5

100B (x2)

390

HE

C1  B5

-3C

 

25mm Objective Crew-Served Weapon

     Notes:  This weapon was designed to partially replace the Mark 19, ASP, and M-2HB.  The OCSWs rounds, like the OICWs grenade launcher rounds, can be set to airburst over a targetís heads or strike the target directly.  The OCSW fires a special 25mm round with a computerized proximity fuse, either HE or HEDP.  The OSCW is fired from a lightweight tripod developed especially for this weapon, or it may be fired from a NHT mount.  The OCSW uses a computerized laser sight, a slightly improved version of the IR imaging sight on the OICW. The OCSW is fed from special cassettes of 22 or 74 rounds. 

     Twilight 2000 Notes: The Objective Crew-Served Weapon (OCSW) was rushed into service several years ahead of its target date, however, few were available by the Twilight War.

     Merc 2000 Notes: Budget cuts largely ended deployment of this weapon.

Weapon

Ammunition

Crew

Set Up Time

Weight

Price

OCSW

25mm OCSW

1

1 Minute

16.5 kg (With Tripod)

$15152

 

Weapon

ROF

Magazine

Range

Round

Damage

Penetration

OSCW

5

22, 74

190

HE

C4  B20

-3C

 

5

22, 74

190

HEDP

C2  B10

23C

 

5

22, 74

190

HEAB

C6  B24

-3C

 

5

22, 74

190

HEDP-AB

C4  B15

23C

 

30mm ASP

     Notes:  The ASP-30 (Automatic, Self-Powered) is a gas-operated version of the 30mm ChainGun designed as an infantry support weapon.  It fits on an NHT or any other mount that is equivalent to an NHT.  It is fed from a 50-round belt.  Recoil is manageable when on a tripod or vehicle mount. 

Weapon

Ammunition

Crew

Set Up Time

Weight

Price

ASP

30mm KCB

1

3 Minutes

48 kg

$20179

 

Weapon

ROF

Magazine

Range

Round

Damage

Penetration

ASP

5

50B

340

APFSDSDU

7

14/12/10/7

 

5

50B

340

API

7

5/4/3/2

 

5

50B

250

HE

C2  B10

-3C

 

5

50B

250

HEAT

C1  B5

29C

 

5

50B

250

HEDP

C2  B10

13C

 

30mm Bushmaster II

     Notes: This weapon is an upgraded M-242 Chain Gun, and retains 70% commonality of parts with that weapon.  The Bushmaster II can use the same ammunition as the GAU-8, and can also fire 30mm Rarden and KCB ammunition.  It is used on US Navy deck mounts, and on the Swedish CV-30, and on some versions of the cancelled AAAV.  It is rumored as an interim upgrade for the Bradley Fighting Vehicle. And the US Marine AAPV-7A1.

Weapon

Ammunition

Crew

Set Up Time

Weight

Price

Bushmaster II

30mm KCB, GAU-8, and Rarden

1

NA

147.4 kg

$20180

 

Weapon

ROF

Magazine

Range

Round

Damage

Penetration

Bushmaster II

5

100B (x2)

625

GAU-8 APIDU

7

17/15/13/8

 

5

100B (x2)

390

GAU-8 HEI

C2  B10

-3C

 

5

100B (x2)

520

KCB APFSDSDU

7

17/15/13/8

 

5

100B (x2)

520

KCB API

7

6/5/4/3

 

5

100B (x2)

390

KCB HE

C2  B10

-3C

 

5

100B (x2)

390

KCB HEAT

C1  B5

29C

 

5

100B (x2)

390

KCB HEDP

C2  B10

13C

 

5

100B (x2)

625

Rarden APDS

7

10/9/7/5

 

5

100B (x2)

625

Rarden APFSDS

7

14/12/10/7

 

5

100B (x2)

520

Rarden APSE

7

6/5/4/3

 

5

100B (x2)

390

Rarden HE

C2  B10

-3C

 

30mm GAU-8/A Avenger

     Notes: The A-10 Warthog CAS aircraft was literally built around the massive GAU-8/A and itís huge ammo drum.  Since then, it has been used on the Goalkeeper CIWS shipboard defense system, better to bring down low-flying missiles at short-range.  As noted above, the 20mm Bushmaster II can also use the GAU-8/Aís rounds.  Warthogs normally carry only APIDU rounds; the Goalkeeper normally uses only HEI rounds.  GAU-8/A rounds are about the size of a milk bottle or, for those youngns who donít remember milk delivery,  a 2-liter Pepsi).

Weapon

Ammunition

Crew

Set Up Time

Weight

Price

GAU-8/A Avenger

30mm GAU-8

1 (3 Loaders on Ground Crew)

6 Minutes (To Reload)

1.584 tons

$46,100

 

Weapon

ROF

Magazine

Range

Round

Damage

Penetration

GAU-8/A Avenger

35

1274 Linkless

2125

APIDU

8

17/15/13/8

 

35

1274 Linkless

1326

HEI

C2  B10

-2C

 

35mm Bushmaster III

     Notes:  This is a belt-fed autocannon which is just beginning to be mounted on AFVs; antiaircraft and naval use is still more common.  The Norwegian variant of the CV-9040, for example, uses the Bushmaster III. 70% of the parts of this weapon are compatible with the Bushmaster I and II.  It fires ammunition identical to that of the 35mm Oerlikon autocannon, though some new warhead types were developed along with the Bushmaster III.  The Bushmaster III has been designed to, after the replacement of the barrel and some minor parts, to be able to fire 50mm Supershot ammunition, effectively becoming a 50mm autocannon.  As of yet, this has not been done on an operational basis, but the concept has been thoroughly tested and is ready for deployment upon request.

     Twilight 2000 Notes: This weapon has been mounted some versions of the M-2 and M-3 Bradley.

Weapon

Ammunition

Crew

Set Up Time

Weight

Price

Bushmaster III

35mm Oerlikon KDA

1

NA

181.5 kg

$35841

 

Weapon

ROF

Magazine

Range

Round

Damage

Penetration

Bushmaster III

5

100B (x2)

390

AHEAD

C2  B12

17C

5

100B (x2)

520

APCI

8

8/7/6/4

5

100B (x2)

520

APDS

8

12/10/9/6

5

100B (x2)

520

APFSDS

8

17/14/12/8

 

5

100B (x2)

520

APFSDS-T

8

20/17/14/9

 

5

100B (x2)

520

APFSDSDU

8

21/18/14/10

 

5

100B (x2)

520

API

8

7/6/5/3

 

5

100B (x2)

520

FAPDS

C1  B5

15/12/11/7

 

5

100B (x2)

390

HE/HEI

C2  B10

-2C

 

5

100B (x2)

390

HEAT

C2  B5

35C

 

5

100B (x2)

390

HEDP

C2  B10

17C

 

5

100B (x2)

390

HEIBF

C1  B12

-3C

 

5

100B (x2)

390

HEINF

C3  B15

-4C

 

5

100B (x2)

520

SAPHEI

C1  B5

7/6/5/3

 

75mm ARES XM-274

     Notes: Initial development of this heavy autocannon began in 1973 as part of the US Armyís HSTV-L and HIMAG programs; the development was sponsored by the US DoDís ARRADCOM Large Caliber Weapons Laboratory, and though the design work was done by ARES personnel, most of the work was done at this facility and ARRADCOM provided partial funding.  The XM-274 was originally going to be used in both a light armored gun system as well as in a self-propelled antiaircraft gun system, but the HSTV-L and HIMAG programs came to naught.  However, in 1981, ARES received renewed interest in the XM-274 from the Army, as possible armament for its RDF/LT program vehicle, the supposed replacement for the M-551 Sheridan at the time.  In conjunction with AAI, a light armored gun system which could be airdropped was designed, using a low-profile turret and a special feed system for the gun.  However, this program too eventually came to naught.  ARES and MOWAG got together and produced a test version of the Piranha II armed with this gun, but no one seemed interested.  Test vehicles with the XM-274 as armament were also made on a LAV-25 chassis, again with no takers. Eventually, the gun was shelved, though ARES still retains the design in their inventory and is willing to put it into production if someone is interested.

     The XM-274 is a heavy autocannon firing revolutionary (for the time) case-telescoped ammunition.  In vehicular applications, the gun is fed from a 36-round carousel in the floor of the vehicle under the low-profile turret, though ARES is willing to consider and has proposed other feed designs.  The CTA ammunition reduces its volume and its weight, as well as making feed more reliable.  The XM-274ís design called electrical priming of the rounds and a recoil/hydropneumatic system for operation.  Spent cases are ejected upwards and outside of the vehicle.  The XM-274 is designed to function optimally firing in short bursts of 1-5 rounds, with a cyclic rate of one round per second.  The barrel is fairly long at L/75.48 (5.661 meters), giving it good accuracy and power despite the relatively small caliber of its rounds.

     At the time of the cancellation of ARESís entry in the RDF/LT program, ARES was working on a 90mm version of the XM-274, but the rate of research was slow as ARES concentrated on the 75mm version, and only two such prototypes were made.

     Twilight 2000 Notes: In the Twilight 2000 timeline, this autocannon is mounted on the LAV-75 light armored gun system.

Weapon

Ammunition

Crew

Set Up Time

Weight

Price

XM-274

75mm ARES CTA

1

NA

1144 kg

$65,410

 

Weapon

ROF

Magazine

Range

Round

Damage

Penetration

XM-274

5

36 Carousel

670

APFSDS

17

97/84/71/46

 

5

36 Carousel

500

HE

C10  B20

4C

 

5

36 Carousel

500

HEAT

C6  B15

68C

 

5

36 Carousel

500

WP

C2  B15

Nil

 

90mm ARES "XM-275"

     Notes: This grew out of the XM-274 project in the early 1980s, when the Army expressed a wish for an ARES/AAI RDF/LT with greater firepower (and they were asking for the same from RDF/LT prototypes in general. The gun was never mounted on a vehicle or even in a mockup or turret; however, the basic gun system was built to the same standards as the XM-274 and AAI drew up plans for a carrier vehicle.  In the end, though, the gun barrel was simply too long and the vehicle itself unable to be airdropped from the C-130 or the C-141 (it was meant to equip the 82n's Airborne in addition to light formations).  The two working prototypes reportedly still exist, but are mothballed.

     The ARES 90mm gun would have required a bigger vehicle with a bigger turret to make room for the gun and it's ammunition.  It too is fed by a 36-round carousel on the floor of the vehicle.  The barrel of the ARES 90mm is not as long relative to its caliber, being 56.61 calibers long.  Optimal fire is still a burst of 1-5 rounds, though ARES recommended 3-round bursts to conserve ammunition and because the rounds themselves are capable of more damage potential than the 75mm ARES rounds.  Operation is identical to the XM-274.

     "XM-275" is the Twilight 2000 designation, or more likely, "M-275."

Weapon

Ammunition

Crew

Set Up Time

Weight

Price

XM-274

90mm ARES CTA

1

NA

1373 kg

$86,443

 

Weapon

ROF

Magazine

Range

Round

Damage

Penetration

XM-274

5

36 Carousel

430

APFSDSDU

20

152/132/112/73

 

5

36 Carousel

320

HE

C16  B30

7C

 

5

36 Carousel

320

HEAT

C11  B20

101C

 

5

36 Carousel

320

WP

C2  B20

Nil

 

5

36 Carousel

160

Flechette

D 30x65; 2d6 Each

1-Nil

 

5

36 Carousel

320

HESH

C11  B20

121C