Categories
Cold War British Prototypes

Centurion Mantletless Turret

United Kingdom (1960s)
Experimental Turret – 3 Built

In recent years, thanks largely to erroneous publications and popular video games such as ‘World of Tanks’ and ‘War Thunder’, a comedy of errors has surrounded the history of the officially named ‘Centurion Mantletless Turret’. This redesigned turret – intended for installation on the Centurion – is often incorrectly identified as the ‘Action X’ turret, with the X being the Roman numeral for 10. It is also known as the ‘Action Ten’ or simply as ‘AX’. In turn, vehicles fitted with the turret, such as the intended Centurion, then have a false suffix attached to them, ‘Centurion AX’ being an example. There is also a false belief that the turret is associated with the FV4202 project, however as we will see, this is not the case.

But what is the truth behind the awkwardly titled ‘Centurion Mantletless Turret’? (for ease this will be shortened to ‘CMT’ throughout the article) Unfortunately, that is currently a hard question to answer, as much information surrounding the turret and its development has been lost to history. Thankfully, due to the efforts of amateur historians and Tank Encyclopedia members Ed Francis and Adam Pawley, some fragments of its story have been recovered.

The first falsehood to tackle is the name ‘Action X’. The name ‘Action X’ appeared in a book published in the early 2000s after the author cited seeing the name written on the back of a photo of the turret. What he fails to mention is that this was written in the 1980s, and does not appear in any official material.

The ‘Centurion Mantletless Turret’ mounted on a Centurion chassis during trials. Photo: The Tank Museum.

Development

By the late 1950s, early 1960s, the FV4007 Centurion had been in service for over 10 years and had already proved to be a reliable vehicle, highly adaptable, and well-liked by its crews. In those 10 years of service, it had already been in use with two types of turrets. The turret of the Mk. 1 Centurion was built to mount the famous 17-Pounder gun. It was roughly hexagonal with a gun mantlet on the leading edge. This gun mantlet did not run the entire width of the turret, but to the left-hand side was a step in the turret face with a large bulbous blister mount for a 20 mm Polsten cannon. The Centurion Mk. 2 brought with it a new turret. While still roughly hexagonal, the large bulbous front was changed to a slightly narrower casting, with a mantlet that covered most of the turret face. The 20 mm Polsten mounting was also removed. Large stowage boxes were added to the outer circumference of the turret and gave the tank its instantly recognizable appearance. This turret would stay with the Centurion for the rest of its service life.

Left, a Mk. 1 Centurion with the original turret, note the 20 mm Polsten mount. Right, a Mk. 3 Centurion with the second turret type, this became the de facto Centurion turret. Photos: Quora & The Tank Museum, respectively

The FV4201 Chieftain was also in development in the early 1960s, and well on its way to becoming the British Army’s next frontline tank. The Chieftain featured a new mantletless turret design. The mantlet is a piece of armor at the breach end of the gun barrel that moves up and down with the gun. On a ‘mantletless’ turret, the gun simply protrudes through a slot in the turret face. With the Centurion proving to be a great export success, it was hoped the Chieftain would follow suit. The Chieftain was, however, expensive.

This would appear to be where the story ‘Centurion Mantletless Turret’ comes in. Evidence suggests that the turret was developed alongside the Centurion and Chieftain, as a means of creating a method for poorer countries to upgrade their Centurion fleets if they could not afford to invest in the Chieftain.

The last surviving ‘Centurion Mantletless Turret’, as it sits today in the car park of the Tank Museum, Bovington, UK. Photo: Adam Pawley

Overview

The design was quite different from the standard Centurion design, but it remained somewhat familiar to existing Centurion operators, foreign or domestic, making the transition easy on potential crews. A large sloped ‘forehead’ replaced the mantlet of the standard turret, with sloping cheeks replacing the vertical walls of the original. The coaxial Browning M1919A4 machine gun was moved to the top left corner of the ‘forehead’, with the aperture of the coaxial gun surrounded by 3 raised ‘blocks’ in the cast armor. The machine gun was connected to the main gun via a series of linkages.

Left, the cheek of the CMT. Right, the cheek of the standard Centurion turret. Photos: Adam Pawley

The gun mount was designed to be adaptable and could carry either the Ordnance 20-Pounder (84 mm) gun or the more potent and infamous L7 105 mm gun, making it ideal for operators of both guns. The gun would pivot on trunnions placed in the slightly bulbous turret face, the location of which is identified by welded ‘plugs’ visible in the turret cheeks. The gun would be aimed via a unity sight that emerged from the turret roof, in front of the Commander’s cupola.

One of the things that the mantlet helps to protect from is shrapnel and debris entering the fighting compartment through the gun mount. In this mantletless design, plating was installed on the inside of the turret to ‘catch’ any fragments that made it through.

The face of the mantletless turret showing the aperture for the main gun. The frame around the aperture is a mounting point for a canvas cover. On the right is a close up of the coaxial machine gun position. Photos: Adam Pawley

Internally, the layout of the turret was pretty standard, with the loader on the left, gunner front right, and the commander behind him in the right rear corner. The decision of what cupola would be equipped on the turret would likely have fallen to the end-user. For the trials, the turret was predominantly equipped with a ‘clam-shell’ type cupola – possibly a version of the Commander’s Cupola No.11 Mk 2. It had a domed two-piece hatch and around 8 periscopes and there was a mounting point for a machine gun. The loader had a simple flat two-piece hatch and a single periscope at the front left of the turret roof.

On the left, the roof of the Mantletless Turret. The cupola is missing from this surviving example at The Tank Museum, Bovington, as is the unity gunsight which would be present in the rectangular slot in the foreground. On the right is the No. 11 Mk. 2 Cupola, while it is not the model used on the Centurion Turret, it is an example of a ‘clamshell’ cupola. Photos: Adam Pawley & Richard Stickland, respectively

The turret bustle stayed the same basic shape, with mounting points for the standard bustle rack or basket. A feature carried over from the standard turret was a small circular hatch in the left turret wall. This was used for loading in ammunition, and throwing out spent casings. On both the left and right turret cheeks, there were mounting points for the standard ‘Discharger, Smoke Grenade, No. 1 Mk. 1’ launchers. Each launcher featured 2 banks of 3 tubes and were fired electrically from inside the tank. The typical Centurion turret stowage bins were also installed around the outside of the turret, although they were modified to fit the new profile.

Unfortunately, most of the armor values of the turret are currently unknown, although the face is around 6.6 inches (170 mm) thick.


Centurion fitted with the Mantletless Turret undergoing trials in the 1960s. Note the unity sight emerging from the top left of the turret roof, in front of the cupola. Also note the 105 mm L7 gun. Photo: The Tank Museum

Not an FV4202 Turret

It is a common misconception that the ‘Centurion Mantletless Turret’ and the turret of the FV4202 ‘40-ton Centurion’ prototype are one and the same. The FV4202 was a prototype vehicle developed to test many of the features that would be employed on the Chieftain. However, these turrets are not the same. While they are extremely similar, there are noticeable differences.

The ‘Centurion Mantletless Turret’ on the left, with the FV4202 turret on the right. The differences are quite noticeable in these shots. Photos: Adam Pawley & fighting-vehicles.com, respectively.

The CMT is far more angular in its geometry compared to the FV4202 turret, which has a much rounder design. The cheeks of the CMT are straight angles where the FV4202 is curved. The trunnion holes on CMT are both in a downward angled section, while on the 4202 the slope is facing up. The armor ‘blocks’ around the coaxial machine gun are also shallower on the FV4202. It would also appear that the gun was mounted slightly lower in CMT. It is not clear as to whether there are any internal differences.

While the turrets are not identical, it is evident that they do share a similar design philosophy, both being mantletless designs with a similar placed coaxial machine gun.

Trials

Just three of these turrets were built, all of which took part in trials undertaken by the Fighting Vehicle Research and Development Establishment (FVRDE). Two turrets were mounted on a regular Centurion chassis and put through a series of tests. The remaining one was used for gunnery trials. While info on most of the tests has disappeared, details of the gunnery trial that one of the turrets – casting number ‘FV267252’ – underwent in June 1960 at the request of the ‘Turret’s and Sighting Branch’ are available.

The turret was subject to fire from rounds as small as .303 (7.69 mm) and .50 Caliber (12.7 mm), through 6, 17 and 20-Pounder rounds, as well as 3.7 in (94 mm) rounds. Both Armor-Piercing and High-Explosive rounds were fired at the turret. The results of the test are displayed below in an extract from the report ‘Trials Group Memorandum on Defensive Firing Trials of Centurion Mantletless Turret, June 1960’.

The full 1960 report on the ‘CMT’ can be found HERE

Conclusion

Of the 3 built, just one of the turrets – casting number ‘FV267252’ from the 1960 report – now survives. It can be found in the car park of the Tank Museum, Bovington. One turret has disappeared, while the other is known to have been destroyed in further firing trials.

Large chunks of the history of the Mantletless Turret remain missing, unfortunately, and the history we do know has been twisted and contorted. The name ‘Action X’ will no doubt continue to plague this turret for years to come, thanks in no small part to Wargaming.net’s ‘World of Tanks’ and Gaijin Entertainment’s ‘War Thunder’ online games. Both have incorporated a Centurion equipped with this turret into their respective games, identifying it as the ‘Centurion Action X’. World of Tanks is the worst offender, however, as they have also mated the turret with the hull of the FV221 Caernarvon and created the entirely fake ‘Caernarvon Action X’, a vehicle that never existed in any form.

Left, the Centurion ‘Action X’ as it is represented in War Thunder. Right, the fake Caernarvon ‘Action X’ in World of Tanks. Photos: Gaijin Entertainment & Wargaming.net, respectively.


Centurion fitted with the Mantletless turret equipped mounting the L7 105mm gun. Illustration produced by Ardhya Anargha, funded by our Patreon campaign.

Sources

WO 194/388: FVRDE, Research Division, Trials Group Memorandum on Defensive Firing Trials of Centurion Mantletless Turret, June 1960, National Archives
Simon Dunstan, Centurion: Modern Combat Vehicles 2
Pen & Sword Books Ltd., Images of War Special: The Centurion Tank, Pat Ware
Haynes Owners Workshop Manual, Centurion Main Battle Tank, 1946 to Present.
Osprey Publishing, New Vanguard #68: Centurion Universal Tank 1943-2003
The Tank Museum, Bovington


By Mark Nash

Member since 2016. Specializes in weird. 113 articles & counting...

8 replies on “Centurion Mantletless Turret”

Huh so this a cent without a mantlet? but… it’s still extreme wrong to see a Caernarvon with a mantletness turret though. I thought that I actually saw a Fv4202 but when this site said it I was pretty disappointed for Wargaming to do this. (;_;).

Why? What are the advantages/disadvantages of mantle, no mantle? I have the sense mantle design predominates. Correct? If so, why again?

There are actually a ton of advantages to the concept, though it mostly has to do with mechanical issues than protection.

The thing is, basically, that in the interwar period to WWII youll see most turrets being designed with a relatively wide mantlet, sometimes even going the entire width of the turret front plate. T-26, BTs, Panzer I II and even III, Panther, Tiger I, Sherman (especially mid and later variants like the 76 and Jumbo), M6 Heavy, T-60/70 and 80 , etc. the list goes on. Even tanks that dont have the mantlet the entire width of the turret, still have a mantlet of relatively substantial width usually, like any T-34 variant, KV, IS-1 and 2, A13s, etc. and relatively few tanks have an actually narrow mantlet (late Crusader, Cromwell, Churchill, late Valentines). There is rhyme and reason behind all of these.

Basically, the point of a mantlet is to provide protection for the aperture where the gun, sight and coaxial machine gun poke through, that will provide no gaps even at full elevation and depression, and the mantlet BEING the turret front was one of the simplest ways to achieve it. Look at the Tiger I for example, the entire mantlet is only a few cm ahead of the elevation trunnion, so moving the gun up and down will only cause the mantlet to rotate but not move vertically by any substantial amount, and there is no front plate where overlapping mantlet parts might interfere on high elevation and depression.
Generally those mantlets were dominant for a while, still being relatively common on some post-war designs like the M46 Patton, the Leopard I and Centurion. But the Tiger II left its mark on tank design, probably being one of the first turret designs to focus on making a narrow frontal section and an even more narrow mantlet, and you can see the idea spreading. IS-3, M47 Patton, M103, M41 Walker Bulldog, Strv 74, Conqueror, T-54 and so forth suddenly adopting turret fronts with very similar advantages (at least as far as the narrow front is concerned, bustles, general height and layout differ a lot by nations preference).
The reason for that is mostly that demands for armor thickness on the turret front increased dramatically, and having a 100mm or heavier slab of metal being attached to the gun put some severe limits on how quickly one could elevate that gun (even if it is balanced). Panthers and Tiger Is already had subpar speeds for elevating guns, if Tiger II went for a similar mantlet with an even heavier gun it would have been beyond even what Germans were generously tolerating so far. Other nations realized the same issue, and demanded not only more resilient turret fronts, but also faster target aquisition, meaning that even with advanced FCS and stabilizers, making sure the elevating part of the gun is as light as possible works to that advantage as well.
Eliminating the gun mantlet entirely is just the next step, making the entire aperture for the gun so small, that giving it any significant armor is unnecessary, thus it being even lighter. Note that the entire shape of the turret got adapted as well to only have a minimal front portion and as much of the frontal sillhouette being parts that angle away into the turret side.
Even on an M1 Abrams the gun mantlet, while being still of noticable size, is consdered narrow enough to not be armored with the same composite as the turret cheeks, as its surmised that only few hits would land there, and most of these would merely disable the cannon, but be of little consequence to the crew or any other critical component.
The German Leopard 2 just has the same composite on the mantlet as the rest of the turret front…..but then again has a mantlet of 1/3 the entire turret fronts width, but apparently its balanced well enough to work with no problems.

I hope I wasnt rambling too much.

I think, you did not added another reason why turret mantlet was needed. It not only provide protection for optics and machine guns, but allows them to be elevated and depressed together with main gun. If you drill a hole into a turret and put optics and machine guns there, they will have better protection (if turret is better protected than a gun mantlet), but tank will be unable to control its fire since you won’t be able to direct your fire nor align optics with your gun.

More modern tanks to my knowledge (early MBTs) just had huge holes drilled into their hull for optics making it another weak spot together with gun mantlet.

https://qph.fs.quoracdn.net/main-qimg-f12465aae03dc65c46426ad7ed205989

Ah, the picture is of the Arjun, which is surprisingly new (and surprisingly shit). They removed a lot of composite behind the optics. Leopard 2 has it similar, but at the same time they added the same amount behind the optic package to not create a weakspot.
But yeah, allowing optics and coax MGs to elevate with the gun is a no-brainer. Its relatively rare that gun, coax and optics are not in a single unit due to having to stay aligned on all elevations. Making them separate just adds complications in the form of linkages and more separate armor pieces to cover several small openings instead of one big one. Practically no tank ever has been designed with no ability to use the gun sight though, even artillery SPGs at least had some sort of open sight for close range fire.

Yes, but even in better designs optics remain a weak spot.

https://lh3.googleusercontent.com/proxy/-XGlhLG4axP_72n3THiGMRT-bGOLlO7N5fLmi52OiXY7KPaW1myGGPgf5vmt6fFiOK9DkLlVVtuGkvGGzOwP0ug8DTUJEn32FKYOQYXqaKcJPsRsumE5pEl2FfNhHfY

http://www.btvt.narod.ru/raznoe/leopard2/Leopard-2-koncpecja.jpg

It has good 200 mm less armor on a huge part of its frontal armor. That is huge. Gun mantlet is even bigger weakspot. While it is assumed that penetration there will only disable the gun, it is still a dangerous mission kill which can injure or kill crew inside with spalling effects or ricochet.

Gun mantle is also massive compared to cold war designs.

http://www.btvt.narod.ru/raznoe/leopard2/Leo2a4/img028.jpg

In conclusion, early modern MBT tanks had flawed turret design with uneven armor and weakspots right in most susceptible and important area on a tank. This is why Rheinmetall later completely remade Leopard 2 turret and had significantly increased its weight during the process. Modern MBT usually does not have such weakspots anymore, but during 80-2000’s such design flaws among tanks were still common place.

Well, 2 of your 3 links were blocked for potentially containing trojans and the remaining one gave me a 403 error on google.

Either way, a shot to the gun mantlet of an Abrams would still be much less likely to harm the crew than a penetrating hit on the turret cheeks, so the priority in armor on the cheeks compared to the mantlet is understandable. The gun can always be swapped out. Crew not so much, training a new crew is way more expensive and will still just give you a fresh crew rather than veterans.
At the same time, a damaged gun breech isnt the only possible mission kill. Damage to tracks, thermal imagers and barrel can also mean a mission kill. Compared to how often those get knocked out, a breech isnt that much of a worry, its just one more part that is expedient as long as the tank remains repairable as a whole.
Im not saying the design is flawless, Im just saying the flaws were generally considered acceptable and didnt prove a major hindrance to the tank as an element of the army.

Hmm, they open fine from my end and even from workplace computer with maximum security settings. It is nothing much. First image is about Leopard 2 image, showing its EMES – 15 commander’s sight. Another one is armor values of Leopard 2 turret. Even with armor there, it still has a lot less of it in there. Third picture is comparing Leopard 2 turret to T-90 turret, showing a lot bigger gun mantlet. You can google them indirectly if you are interested.

The reason why those tanks had those optics were was for simplifying optics and thermal sight in the main commander’s sight as far as I know. Back when sensoric technology did not matured to such a point that we can just add camera wherever on a tank and link it to computer in a tank. Gun mantlet is as it is for the sake of simplicity and maintenance. Such mantlet allows a lot easier replacement of a main gun and quite possibly upgrading to different types of guns. You can take out entire gun with its mantlet out of Leopard 2 tank and replace with a brand new gun without removing entire turret which makes whole process a lot easier.

The difference here is that EMES-15 optic sight and gun mantlet creates threat to structural integrity. Or in other words, allow a penetrative hit to happen when normally it should not happen. This is especially problematic with modern tank warfare tactics where tank drives to the ridge, exposes itself for few seconds, fires and falls back. Inconsistent turret armor can cause a loss of a tank where it would otherwise just disable tank for that mission.

Designers at that time had made a compromise. They sacrificed consistent frontal protection for other priorities like optics or maintainability. However, it does not mean that we should not criticize this aspect of Leopard 2 early models, especially when designers themselves had fixed those issues. It does not make Leopard 2 “trash” or a “bad” tank by any metric, however in this very specific point we should acknowledge that design sacrifices which designers consciously made had created very inconsistent frontal turret armor profile for Leopard 2 with massive surface area of significantly weaker turret armor.

Personally, I would not had made those choices as I value armor protection consistency quite highly, especially on the turret front. These flaws makes it impossible for early Leopards 2 to use previously mentioned tactic effectively as a return fire from near peer adversary can destroy entire tank when otherwise it would not. I’m also highly critical of loose ERA protection on a Russian designed tanks, but that is the topic for another time. Maybe when Tanks Encyclopedia makes an article on some of those tanks I will be able to rant how poorly protected they are, eh? 🙂 

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