A.C.IV

A.C.IV

A.C.IV

Britain

III Rank

Battle rating:

AB	RB	SB
5.3	5.3	5.3

Class:

PREMIUM

Medium tank

Purchase:3 410

Description

Australia began the development of the A.C.IV Sentinel as the A.C.I intended to fulfil the role of a cruiser tank. A commission was sent to the US to investigate the M3 Medium Tank since Australia lacked any kind of experience in armour development. It was decided to try a concept similar to the Canadian Ram, using the M3 as a basis and working around its design. Some other parts of the design were also based on the British Crusader tank. The tank was meant to be armed with a 2-pounder gun, but this was increased to a 6-pounder in future variants. The final version, the A.C.IV, was developed to use the new and more powerful British QF 17-pounder gun, capable of dealing with the best German tanks at the time. The turret ring was also increased to 70 inches, for greater crew comfort.

It was released some time after Update 1.55 "Royal Armour". The A.C.IV is a well-rounded tank with superior armour layout compared to other British tanks at its BR; it can occasionally bounce shells from Tigers and Panthers if lucky. It is a relatively small medium tank in comparison to the common mainstay of the other countries, especially when compared to the American Sherman tanks. The Sentinel also has a good manoeuvrability and power-to-weight ratio for the propulsion, able to accelerate to its max speed of roughly 30 km/h quickly and stay there on stable terrain. The tank has a great advantage of a decent reverse speed in comparison to other medium tanks of its calibre, with a reverse speed almost the same speed as forward. The addition of the 17-pounder gun also gives this tank strong firepower for its size, so it can stand a chance against tanks of the same tier despite being out of the league in terms of armour.

General info

Survivability and armour

Armourfront / side / back

Hull64 / 45 / 45

Turret64 / 64 / 64

Crew4 people

Visibility91 %

The AC IV Thunderbolt is one of the few British tanks at this BR with sloped armour rather than the traditional boxy armour found in other British tanks. Its armour has a high tendency to bounce shells. This is obvious with the extreme slope on the from of the tank, and turret design. The armour itself is not thick, but thanks to the angle of it this tank can be very fierce competition to enemy vehicles. Although the armour is superior to that of other British tanks, it is not recommended to rely on it too heavily. Other nations, particularly the Germans, have no trouble penetrating the tank from any range. Because the crew compartment is relatively cramped, any penetrating shots can be fatal. The side armour on the Sentinel is extremely weak and vulnerable to SPAA flanking.

Armour type:

• Cast homogeneous armour
• Rolled homogeneous armour (Hull roof)

Armour	Front	Sides	Rear	Roof
Hull	50.8 mm (66-67°) Frontal glacis 50.8 mm (30°) Driver's port 50.8 mm (7-68°) Lower glacis	44.45 mm (0-12°)	22.22 mm (78°) Top 44.45 mm (21-52°) Bottom	22.22 mm
Turret	63.5 mm (4-47°) Turret front 25.4-63.5 mm (1-68°) Gun mantlet	63.5 mm (0-88°)	63.5 mm (1-53°)	35 mm
Armour	Sides	Roof
Cupola	63.5 mm	35 mm

Notes:

• Suspension wheels and bogies are 20 mm thick, tracks are 20 mm.
• The rear bottom area has a track placed there, providing 20 mm of extra armour.
• The commander cupola is extended outwards from the left side of the turret, creating a vulnerable unsloped area vulnerable to weaker guns.

Mobility

Speedforward / back

AB54 / 11 km/h

RB and SB48 / 10 km/h

Number of gears5 forward

1 back

Weight26.4 t

Engine power

AB757 hp

RB and SB397 hp

Power-to-weight ratio

AB28.7 hp/t

RB and SB15.0 hp/t

The AC.IV has an overall good mobility, with an acceptable reverse speed not found in other British tanks (e.g., Challenger, Comet, etc.). The manoeuvrability in soft terrain can be significantly reduced and can feel sluggish.

Game Mode	Max Speed (km/h)		Weight (tons)	Engine power (horsepower)		Power-to-weight ratio (hp/ton)
	Forward	Reverse		Stock	Upgraded	Stock	Upgraded
Arcade	54	11	26.4	615	757	23.3	28.67
Realistic	48	10		351	397	13.3	15.04

Modifications and economy

Repair cost

AB1 319

RB1 532

SB2 031

Crew training10 000

Experts250 000

Aces630

Research Aces870 000

Reward for battleAB / RB / SB

2 × 90 / 150 / 180 %

2 × 160 / 160 / 160 %

Modifications

Mobility	Protection	Firepower
Tracks Suspension Brake System Filters Transmission Engine	Improved Parts Improved FPE Crew Replenishment	76mm_britain_17pdr_APC_ammo_pack Horizontal Drive 76mm_britain_17pdr_APCBC_ammo_pack Adjustment of Fire Elevation Mechanism Artillery Support 76mm_britain_Smoke_ammo_pack

Armaments

Main armament

76 mm QF 17-pounder cannon

Ammunition50 rounds

Reloadbasic crew → aces

7.6 → 5.9 s

Vertical guidance-10° / 20°

The classic Ordnance QF 17-pounder is a very powerful gun: its performance against Tiger I and Panthers is very consistent and satisfactory. The Sentinel offers a smooth gun handling, with a good turret traverse speed and a good gun elevation speed. It has an excellent gun depression of -10 degrees and offers a small silhouette when hull down, comparable to the Comet. Because British tanks do not have access to APHE shells, any shot fired must be accurate; always aim for crew compartments and vital components of enemy tanks.

76 mm QF 17-pounder					Turret rotation speed (°/s)					Reloading rate (seconds)
Mode	Capacity	Vertical	Horizontal	Stabilizer	Stock	Upgraded	Full	Expert	Aced	Stock	Full	Expert	Aced
Arcade	50	-10°/+20°	±180°	N/A	17.14	23.72	28.80	31.85	33.88	7.67	6.79	6.25	5.90
Realistic					10.71	12.60	15.30	16.92	18.00

Ammunition

Penetration statistics
Ammunition	Type of warhead	Penetration @ 0° Angle of Attack (mm)
		10 m	100 m	500 m	1,000 m	1,500 m	2,000 m
Shot Mk.6	AP	171	168	155	139	126	113
Shell Mk.1	HE	20	20	18	16	15	13
Shot Mk.4	APC	171	168	155	139	126	113
Shot Mk.8	APCBC	190	187	172	155	140	126

Shell details
Ammunition	Type of warhead	Velocity (m/s)	Projectile mass (kg)	Fuse delay (m)	Fuse sensitivity (mm)	Explosive mass (TNT equivalent) (g)	Ricochet
							0%	50%	100%
Shot Mk.6	AP	883	7.71	-	-	-	47°	60°	65°
Shell Mk.1	HE	883	6.98	0.2	0.1	580	79°	80°	81°
Shot Mk.4	APC	883	7.71	-	-	-	48°	63°	71°
Shot Mk.8	APCBC	883	7.71	-	-	-	48°	63°	71°

Smoke shell characteristics
Ammunition	Velocity (m/s)	Projectile mass (kg)	Screen radius (m)	Screen deploy time (s)	Screen hold time (s)	Explosive mass (TNT equivalent) (g)
17pdr Shell SS Mk.1	229	8.44	13	5	20	50

Ammo racks

Full ammo	1st rack empty	2nd rack empty	3rd rack empty	4th rack empty	5th rack empty	6th rack empty	7th rack empty	8th rack empty	9th rack empty	Visual discrepancy
50	45 (+5)	39 (+11)	35 (+15)	31 (+19)	25 (+25)	19 (+31)	15 (+35)	11 (+39)	1 (+49)	No

Ammo racks of the A.C.IV

Notes:

• Racks disappear after you've fired all shells in the rack.

Optics

A.C.IV Optics
Which ones	Default magnification	Maximum magnification
Main Gun optics	x1.85	x3.5
Comparable optics	T-34-57

Does not have improved zoom like the other rank III British tanks of similar BR, thus has worse zoom than many of its opponents, which may have variable zooms up to X5. Do not unnecessarily provoke German SPGs, as they have superior optics and are unlikely to miss.

In full up-tier, do not let Japanese medium tanks (e.g. ST-A1) get an upper hand at all costs, as they have optics eclipsing these entirely and can easily snipe A.C.IV from 2 km away, with accuracy modifications.

Machine guns

7.7 mm Vickers machine gun (coaxial)

Ammunition4 250 rounds

Belt capacity250 rounds

Reloadbasic crew → aces

10.4 → 8.0 s

Fire rate390 shots/min

There is only one 7.7 mm coaxial MG with a very slow rate of fire, and no roof-mounted MG to defend against incoming planes. The small calibre of the Vickers machine gun makes it largely ineffective against all armoured vehicles but the ones with an open compartment. It still can be used to ping targets as a rangefinding help. While the belt capacity of the machine gun is adequate, its rate of fire is extremely slow for the battle rating.

7.7 mm Vickers
Mount	Capacity (Belt)	Fire rate	Vertical	Horizontal
Coaxial	4,250 (250)	390	N/A	N/A

Usage in battles

Exploit the A.C.IV's manoeuvrability against the heavier tanks, plus the 17-pounder tank allows for a penetration through the enemy's armour to cause internal damages. The fast reverse speed makes the "shoot-and-scoot" tactic a viable method against the enemy, and should be the prime one as the armour of the Sentinel is not exactly the most durable at only 50 mm flat.

However, the sloping nature of the armour could give the bouncing capability of the tank comparable to the T-34, it's even arguably much better. So while the weight class is definitely against the Sentinel, a chance is always there to take out the opposition. When compared to other British tanks, this tank lacks access to APDS rounds. Extra caution should be paid during full uptier matches as there will be many enemy tanks, particularly German tanks, that this tank will find difficult to engage from the front.

"Shoot-and-scoot" tactics are the best tactics to use with this vehicle. The Sentinel's armour does not let the tank be a brawler, so it must be more "sneaky" against the enemies. Another thing to note is the driver's hatch at the front of the tank. To avoid a frontally penetrating shot, always angle the driver's hatch away from the enemy.

The A.C.IV is quite mobile, even for a medium tank. Compared to tanks of similar BR like the Shermans and the T-34-85s, it has a very good reverse speed that is specially good when it's used in close quarter scenarios. That means that when it's used in city maps, the A.C.IV is very good for performing ambushes and setting up traps for heavier enemy tanks. It is also very capable in flanking manoeuvres, its gun is excellent to deal with enemies from the front, but it lacks the APHE rounds present in tanks from other nations.

This means that the best round available for the A.C.IV is the Shot Mk.8 APCBC round. It is recommended to take at least 5 HE rounds to deal with enemy SPAA and any kind of open top vehicle (to one shot them with overpressure) and 25 rounds of APCBC. More rounds can be taken, but it's recommended taking only 30 to reduce the chances of ammo detonation, but even with that, there is a lot of empty space inside the A.C.IV, so even with a full ammo load, ammo detonation is rare to say the least.

When playing in a downtier, the armour of the Sentinel becomes much better, it can reliably bounce shots with good positioning and angling of the chassis, but in downtiers it can be used as a brawler, attacking enemy tanks from the front and using the good penetration of its QF 17-pounder cannon. And in open maps with little to no cover, stay close to your team, since this tank can't brawl the same way heavy tanks will, even in full downtiers. There, the good mobility of the Sentinel can be a great advantage to cover capture points.

Pros and cons

Pros:

• Good sloped armour
• High penetration solid shot rounds
• Good manoeuvrability
• Fast reverse speed
• Small profile

Cons:

• Sloped armour only on the front
• Susceptible to large calibre HE shells
• Only 44 mm of side armour
• Cannon lacks armour-piercing rounds with high-explosive filler
• No APDS rounds, unlike other British medium tanks at this rank
• Single 7.7 mm coaxial MG with a very slow rate of fire

History

Development

Australia began designing a tank in November 1940 as the AC I, and was intended to be a cruiser tank weighing between 16 to 20 tons with a 2-pounder gun. With no prior experience in producing a domestic tank, Australia sent a task force to the United States to study the M3 Medium design to understand the in-and-outs of a tank. They also received the aid of Colonel W.D. Watson MC in December 1940 from Britain, who has many years of tank designing experience. The overall mission ended up having the tank design to have a similar concept as the Canadian Ram tank, being based off the the M3 Medium chassis and mated with a domestic design of their choice for the upper part along with the incorporation of a suspension system of horizontal rubber cylinder springs seen on many early-war French tanks notably the H.39 and H.35. The Australian attached the chassis with a hull and turret with design similarities to the British Crusader tanks. The design started to become less of a cruiser tank and more of a medium tank by American specifications due to the attempt to up-armour and up-gun the tank to keep up with German armour development.

The first design was completed in February 1942 as the Cruiser Tank Mark 1 (AC I) and designated the "Sentinel". The design was simplified by using existing parts of current tanks and using a cast hull and turret. The entire hull being casted would be the first in history as many tanks of the era did not use such techniques. Although originally specified for a 2-pounder, it was then asked for a 6-pounder armament but due to the manufacturing of such guns not begining at the time in Australia they would have to use the 2 pounder for the first 65 produced. Two Vickers machine gun were used as the coaxial and hull machine gun the later having an armoured mount to protect its water sleeve resulting in a rather lewd looking front of which is made fun of to this day. With the power of three Cadillac V8 Petrol engines. It was unorthodox, but powerful enough to propel the vehicle. 65 of these tanks were made by June 1943 before being succeeded by a more advanced design known as AC III, also known as the "Thunderbolt". It had better armour and an improved firepower in the form of the 25-pounder howitzer. Despite the bigger gun, the 54-inch turret ring was never expanded to accommodate for the gun's larger size, so the crew experienced a slightly cramped turret interior for the benefit of having a better high-explosive charge and armour-piercing capability. Other differences in the design was the removal of the hull machine gun and a different set-up of the three Cadillac engines. One pilot model was built and plans were made for a production for 25 tanks for further trials, but the program was terminated.

Another attempt was made to increase Australian tank firepower with the AC IV design. It first started when the designers check to see if the turret could mount the massive 17-pounder in use by the British to fight the heavier and more protected German tanks. When the tests proved successful, the 17-pounder was chosen to be the gun for the AC IV, with a new and larger turret and 70-inch turret ring to improve crew comfort. These tanks were only made for evaluation purposes only and were never mass-produced for equipping the armoured units. However it would be the only commonwealth tank ever to mount such a gun.

Termination

The AC IV design, along with the entire Australian Cruiser tank program, was terminated in July 1943, ending with only 65 tanks produced and a few prototype models. The reason was that the funds were better spent improving the infrastructure than building new tanks due to the large number of American tanks such as the M4 Medium that were being supplied to Australia. The AC "Sentinel" were all put into storage and kept until the end of the war. The only use the Sentinel saw was in the film The Rats of Tobruk in 1943 when a squadron of AC I tanks were modified to resemble German tanks.

Survivors

After the war, the Australian government disposed most of the tanks in 1945, most were sold off by the Commonwealth Disposals Commission. Today, about six Sentinels survive in intact conditions across the world. One notably in the Bovington Tank Museum, and three in Australia in the RAAC Tank Museum, Treloar Technology Centre, and one in the United States in the Collings Foundation.

Media

Skins

• Skins and camouflages for the A.C.IV from live.warthunder.com.

Videos

Australian Cruiser Tanks - AC I "Sentinel" - AC IV "Woomera" (review starts at 5:20) - Cmdr. Tyrael

AC IV Thunderbolt - Ash

See also

Links to the articles on the War Thunder Wiki that you think will be useful for the reader, for example:

• reference to the series of the vehicles;
• links to approximate analogues of other nations and research trees.

External links

• [Devblog] AC IV Thunderbolt

New South Wales Railway Company
Medium tanks	A.C.I · A.C.IV