Debate on using autoloader or manual loading of tank gun has been going on since autoloaders had first appeared. And it has not not been resolved yet, as can be seen from various solutions currently in service. But in general, Western designs have opted for manual loading while Eastern designs had opted for autoloaders.
So what are advantages and disadvantages of using autoloader? Here, I will be considering two main autoloader designs: the cassette and the carousel. Former is used in e.g. Leclerc, Type-90 and Ukrainian M-84 Oplot M, while latter is used in Soviet designs such as T-72 and its derivatives. While there are other types of autoloaders, most of them have similar advantages and disadvantages to either cassette type (e.g. revolver / bustle carousel) or carousel type. In any case, the cassette and the carousel are the most common solutions for autoloaders.
Rate of Fire
One factor commonly cited as an advantage for manual loader is the speed of loading. But as with everything: it depends.
With manual loading, there are many factors which can impact how quickly a loader can load the round. Tank with manual loader has an ammunition ready rack, which in M1 Abrams is 18 rounds, and 15 rounds in Leopard 2A4. Abrams also has a semi-ready rack of another 18 rounds. In Leopard 2, remaining ammunition is in the hull and turret has to be rotated for the ammunition to be transferred to the bustle, making tank highly vulnerable in the process. M1 Abrams also has hull stowage of 6 rounds, but that is usually used to hold alcohol and other stuff slightly more illegal and less dangerous than ammunition.
Both manually loaded and autoloaded tanks have to get their guns reset to loading position in order to be reloaded properly. In M1 the switch is manual, while European designs reset the gun automatically after being fired. Once the gun is reset, a manual loaded tank has to have the loader open the armored door (which is hydraulic), take out the round, load it, close the door, and only then gun can be fired. In M1 Abrams seen in the Chieftain’s video, the process takes some 10 seconds, and elsewhere rate of fire of 8 rounds per minute – or 7,5 – 8,5 seconds to reload – is quoted. In emergency, reloading the gun itself may take some 3 – 5 seconds. But this is eminently unsafe: to achieve 3 – 4 second reload in Leopard 2, blast doors have to be kept open, which means that any penetrating hit to bustle will kill everyone. And once the rounds in the sweet spot had been spent, loader has to start hunting for the next round, which increases the reload time – much like in the autoloader.
With autoloader, there are again different factors. Where the round is positioned in the loader matters. T-64 and T-80 use a carousel autoloader, with minimum reload speed of 6 seconds if rounds are next to each other (of the same type) and 13 seconds with full carousel rotation. T-90 can reload in some 5 – 8 seconds. T-72 has the slowest autoloader of modern main battle tanks, with minimum reload time of 6,5 seconds and maximum reload time of 15 seconds. Bustle autoloaders however are much faster than carousel autoloaders. Japanese Type 90 main battle tank can reload the round within 4 – 6 seconds of the previous round being fired. French AMX Leclerc has reload speed of 6 seconds regardless of whether stationary or on move, but rate of fire when on the move appears to be one shot every 10 seconds. Ready ammunition is similar in all cases. T-64 and T-80 have 28 rounds in the autoloader, while T-72 and T-90 have 22. Type 90 has 19 rounds in a turret, while Leclerc has 22. This is less than M1 Abrams with its 36 ready rounds in the bustle, but the reason is simply smaller turret rather than anything to do with autoloader itself.
And when gun resets, targeting system in fact remains on the target. This is again true for both manually loaded and autoloaded guns. As a result of all these factors, manual loading provides no advantage in maximum rate of fire, while autoloader has advantage in sustained rate of fire as human loader tires over time. Last point may or may not be an issue with 120 mm, but anything above requires autoloader. And if tanks go to 130 mm guns, then autoloader is simply a must.
Even if – and this is not certain – manual loader can achieve higher burst fire, this does not really matter. Either enemy tanks are poor shots or outranged, in which case faster burst fire is irrelevant, or they are not, in which case engaging tank has to go back into cover immedately after the first shot where it can reload in peace regardless of whether it is using manual loader or autoloader. And if the enemy is in range, a good shot, not dead after the first shot, and there is no cover, then the engaging tank will be hit (and possibly killed) by return fire regardless of whether it is using human loader or autoloader. In these conditions, more armor becomes more important than maximum rate of fire – which again advantages the autoloader (see the weight table in “mobility” section).
Firepower
With bustle storage, rounds can be made as long as necessary, so long as the bustle accepts them – and the bustle can be extended. This is true for both manual loading and autoloaders. Carousel autoloader however has the limitation on length of the rounds which is determined by the turret ring diameter. This means that carousel autoloader uses much shorter ammunition – which usually leads to utilization of two-piece ammunition.
This is not much of an issue in terms of rate of fire (though it does add a second to loading process compared to the same design with one-piece ammunition), but it is an issue with sabot performance. Splitting the round into two means that sabot has to be much shorter, which negatively affects the armor penetration as the crossectional density is lower.
Another solution might be telescoped ammunition, but even there the bustle autoloader would keep the advantage.
Survivability
One reason why autoloaders get a bad rep in certain circles are the tales of the Soviet-design tanks exploding in wars – such as current war in Ukraine, or the Battle of Vukovar with its tank graveyard at Trpinja road. But while this criticism is partly valid, it applies only to Soviet-type carousel autoloader, and even then only conditionally.
Bustle autoloader is in fact safer than bustle storage in a manually loaded tank. This is for several reasons. First reason is that the door in the bustle wall through which ammunition is loaded only need to accept one round to pass through. With a fully manual loading process, the opening has to cover the entire ready rack. This means that a) doors are slower to open and close due to larger size and b) potential for catastrophic damage if the tank is hit while the doors are open is much greater. In fact, loaders often leave the doors open while loading to expedite the process. For this reason, semi-autoloaders have been created, where autoloader feeds the round to human loader (e.g. Merkava). Second reason is that the turret can be smaller and better armored, at least if sensors and armament configuration is similar. Third reason is that the tank overall can be somewhat smaller, which is a survivability bonus by itself.
Carousel autoloader is much less safe than either – but not necessarily because of the autoloader itself. T-72 has roof on the autoloader which reduces the probability of the ammunition there cooking off due to penetrating hits (spalling etc.), but this does nothing to protect ammunition outside the autoloader, nor is it enough to prevent the ammunition in autoloader from cooking off should ammunition in the crew compartment cook off. And it is the ammunition in the crew compartment that was the leading case of losses of Russian-model tanks. Good case study are two battles of Grozny. In the first battle of Grozny, Russian tanks suffered typical catastrophic losses. But in the second battle of Grozny, Russian tankers were ordered to remove all the ammunition outside the autoloader. This one measure dramatically improved survivability: some tanks reportedly survived ten or more penetrations by RPG. But removing the ammunition from crew compartment significantly limits the available ammunition, as autoloader can hold only 20 – 22 rounds. Ukrainian tankers in the current war in fact only leave the autoloader ammunition, and go to battle with 22 rounds in it. And autoloader may still be vulnerable to top-attack ATGMs.
Carousel autoloaders also do not have blowoff panels, perhaps because with their round shape the blowout panels would be more difficult to properly install. But this argument is much less important than it may seem to be. In fact, the M1 Abrams is the only tank in the world whose ammunition is entirely protected by blowout panels. Challenger 2, Leclerc, Leopard 2, Merkava, Type 10, K2, Type 90 all carry at least some ammunition in the hull, where results of a hit will be similar to a hit to Russian carousel autoloader. Even if none of these tanks manage to dethrone Russian designs in their turret launching championships, explosion of ammunition within the tank is nevertheless unlikely to be survivable. In fact, the only way to make hull stowage completely safe would be to either a) completely separate the crew areas from the ammunition (e.g. crew in a capsule in front of the hull, ammunition in carousel in the center) or b) only store inert rounds there (which would mean two-piece ammunition as all propellant as well as explosive projectiles – be it HE, HESH or HEAT – would have to be in the bustle).
Overall, a carousel design with separate crew compartment and an unmanned turret would still offer the same crew survivability benefits as the bustle design. Disadvantage is that tank would certainly be a complete writeoff whereas a tank that has had ammunition in bustle cooked off may be returned to service (in theory, anyway). Good solution may be to utilize bustle for explosive propellant and ammunition, with carousel for inert kinetic penetrators – something USSR had experimented with, but never implemented.
Mobility
One reason why Russian tanks have gone for the carousel autoloader is mobility, tactical and strategic both. In terms of volume, Soviet tank designs are much smaller than most Western equivalents.
And this is significant. Modern tanks weight up to 70 tons, which is the practical limit for today’s infrastructure. See the table below:
| MANUAL LOADER | AUTOLOADER | ||
| Ariete | 54 t | Leclerc Series 1 | 54,5 t |
| Challenger 2 | 64 t | Leclerc Series 2 | 56,3 t |
| Challenger 2 | 75 t | Leclerc Series XXI | 57,4 t |
| Leopard 2E | 63 t | K2 Black Panther | 55 t |
| Leopard 2PL | 59 t | PT-91 Twardy | 45,9 t |
| Merkava Mk IV | 65 t | T-84 | 46 t |
| Challenger 3 (proj.) | 66 t | T-90 | 46 t |
| M1A2 | 62,1 t | T-90A | 46,5 t |
| M1A2SEP | 63 t | T-90SM | 48 t |
| M1A2SEPv2 | 64,6 t | Type 10 | 44 t |
| M1A2SEPv3 | 66,8 t | Type 96 | 41 t |
| Type 96A | 42,8 t | ||
| Type 96B | 43 t | ||
| Type 99 | 51 t | ||
| Type 99A | 55 t | ||
| M-84D | 48,5 t | ||
| T-14 Armata | 55 t | ||
| AVERAGE | 63,9 t | AVERAGE | 49,2 t |
| AVERAGE Western | 55,8 t | ||
| AVERAGE Eastern | 47,1 t | ||
As can be seen, Western designs with autoloaders are on average 8,1 tons (12,7%) lighter than Western designs with manual loading. Eastern designs with autoloader (carousel) are on average 16,8 tons (26,3%) lighter than Western designs with manual loading. This means that they use less fuel, are easier to transport by rail, truck or air, can use more bridges and better navigate rough terrain due to smaller dimensions, higher power-to-weight ratio and lower ground pressure. They are also more capable of operational and strategic deployment. Alternatively, weight can be kept the same, but with far better protection. And all these weight savings would be far more pronounced in a tank with an unmanned turret.
Note: Panther KF51 is excluded since it actually has four crew members. Including it, at 59 t weight, would make Western designs with autoloaders on average 7,5 tons (11,7%) lighter than Western designs with manual loading.
Reliability
Both autoloaders and human loaders can break down, but swapping a crewmember is much easier than swapping a massive piece of machinery. However, autoloader is only one piece of an extremely complex machine, and modern tanks are crammed full with different pieces of machinery.
And autoloaders are in fact very reliable. TTB autoloader completed 61 000 cycles without failure. For comparison, large-caliber tank barrel can fire on the order of 100 to 1 000 EFC (Effective Full Charge – that is to say, equivalent of the most damaging to the barrel round) before being replaced. This means that TTB’s autoloader will have seen at least 61 barrel changed before experiencing a single failure. It should also be noted that TTB’s autoloader was of a carousel type, with ammunition on the turret ring floor. This setup requires fairly complex loading process and mechanisms compared to the bustle autoloader, making it much less reliable than a bustle autoloader, as well as being more susceptible to accidental damage by the crew. A bustle autoloader can be expected to be even more reliable than TTB’s autoloader due to a much simpler design and reload cycle. Even if autoloader breaks down, many tanks equipped with autoloaders also have provisions for manually loading the gun, though this significantly reduces the rate of fire – T-72 in manual mode requires about a minute for the gun to be reloaded.
One disadvantage of the autoloader is that there is no extra crewmember to replace gunner, commander or driver if any are down. But considering how dangerous modern battlefields are becoming, it is questionable whether open-hatch driving is a smart idea, making it less likely that only one crewmember will be injured or killed, or even that any will be injured without a tank also being mission-killed at least.
What is disadvantage of an autoloader is potential loss of power. Everything on a tank can be operated with no power in case damage kills the power. But in such conditions, tanks that are manually loaded by default are in a far better position than tanks designed around an autoloader.
Maintenance
The only real issue with an autoloader is that removing one person means that there is one person less available to do maintenance on the tank while maintenance requirements themselves are increased by addition of a fairly complex piece of machinery. But this is not necessarily true. A tank company is not just tanks, and even with tanks there is no rule stating that crew has to be limited to just however many can fit within the tank. An attached APC platoon with additional maintenance crews can easily solve this problem while still having fewer people in the line of fire. Maintenance tasks may also be pooled in the unit, with APC and IFV crews and/or infantry helping with tank maintenance and vice-versa.
When it comes to crew themselves performing maintenance, responses vary. However, it seems that regular maintenance and inspection requires only two men, and anything above that requires specialized maintenance crews or assistance from the side. Based on this, it does not seem that autoloader is a disadvantage.
Other
One issue with autoloader is that round cannot be extracted once it had been fed into the barrel. But this is in reality a non-issue. Even on manually-loaded tanks, tankers are trained to fire off the round already in the gun and then switch to proper round on a follow-up. Reason for this is because it is both faster to fire off the loaded round, as well as being safer – even with fully-cased ammunition, round could get damaged and spill the propellant all over the vehicle when being unloaded.
Carousel autoloader makes it difficult to upgrade the tank with e.g. longer subcaliber penetrators, as that would require increase in autoloader diameter, turret ring diameter… leading potentially to need to design a whole new tank. A tank using manual loading or else bustle autoloader is much easier to upgrade. Carousel autoloader is likewise much more difficult to reload as rounds have to be lowered through the hatch. This however is the normal practice for bustle storage as well, even though in theory rearming the bustle-equipped tank can be done by simply taking out the empty magazine and lowering in the full one.
While speed of manual loading receives much focus in discussion of tank-on-tank engagements, history – both far away and recent – has shown that the main killer of tanks is basically anything other than tanks. Tanks have to have capability to destroy other tanks, but that is merely one of many capabilities tank has to have – and not the most important either. Neither is a tank the only type of vehicle on the battlefield, or the only type of combat vehicle in a tank unit.
Conclusions
Overall, with the exception of an argument on maintenance, there appears to be no real reason not to use autoloader in a tank. The real reason not to do it is simply that army is a bureaucracy, and thus has massive institutional inertia. There are however good reasons to avoid the carousel autoloader, though survivability is not actually the biggest one, as significant as it may be.
History and War 