A few weeks ago a blog post discussing Swedish artillery at the brigade level caught my eye. As I noted last year,Finland is looking at the retirement of a significant portion of our brigade level assets in the near future, and which system should replace these is far from obvious. The post by Öhman was also of the kind of outside the box thinking I like to bring forward, so I contacted him and asked for permission to run an English translation. The translation is my own, and all faults when it comes to jargon are my own work as well.
The author Peter Öhman is a Swedish officer with a solid knowledge of anything armour or artillery who currently works at the Swedish Defence Material Administration. You will find him on Twitter and on his blog.
In a future growing Army there are many who feel that Haubits 08 ‘Archer’ would be optimally used as a divisional asset. It is a sensible idea which has been discussed in many places, but which won’t be developed further here.
With Haubits 08 as a divisional asset there would appear a void on the brigade level, as we don’t have any towed Haubits 77 mothballed. What should then be the remedy?
If one looks at the different requirements for a brigade-level artillery system they could look something like this:
- Instantaneous firepower that allows a unit of size X to fire a fire mission in under 10 seconds,
- Accuracy that allows the fire mission to hit the target location,
- The ability to maintain sustained fire for X amount of time,
- Protection which allows the artillery unit to operate together with the rest of the brigade,
- Mobility which allows the artillery unit to move with the brigade’s battle,
- High availability.
In practice this means that the artillery piece must have a certain rate of fire, especially initially. The ability to sustain fire over time is created by bringing lots of ammunition, having the ability to reload rapidly, having an efficient logistics chain, and sporting a high resistance to the barrel heating.
Protection means protection against shrapnel, but also signature reduction and the ability to rapidly move to a new position after firing. When discussing mobility it is easy to get dragged into a discussion about tracks or wheels, which is a balance between the ability to quickly transfer between battalions and cross-country mobility to reach suitable firing positions in the terrain. Very few today consider using towed pieces, due to the longer time to get them into position.
High availability may be technical reliability, but it may also be based on mobility, and perhaps most of all range.
As the requirements are broken down into details, sooner or later the question about what calibre should be used will become the topic of the day.
Of what calibre should a future system be?
155 mm is of course the NATO-standard and a calibre which has been working well since at least the Second World War. We can’t abandon a NATO-standard by ourselves, and we have old ammunition stocks which we need to be able to use. That’s how easy the analysis can be. Now is when I will be unreasonable and question this train of thought. Is 155 mm really an obvious choice for supporting the fighting formations of a brigade? The following text should be treated as something of a “military satire”.
If we look at the specifications for a number of common artillery systems in 152 and 155 mm we get the following table:
|System||Weight (t)||Range (km)||Am. carried||Shots/min||Length||Crew|
Ranges given are for standard rounds, i.e. not including base bleed or similar technologies.
When looking at even large calibers such as 203 mm the big benefit of 155 mm is that it is easier to handle both for humans and machines. A 155 mm shell weighs around 45 kg, compared to at least twice as much for a 203 mm one. The recoil forces are also about twice as big, leading to an unreasonably large gun. The range will also be short unless one want a barrel that is 2.5 m longer than the already long 155 mm L/52 barrels. Big and heavy ammunition also leads to a low rate of fire. The US M110 howitzer with an L/25 barrel has a range of 17 km with standard ammunition. Weighing 28 tons it only carry two rounds. This means a continuous supply of ammunition is required, and even in the best case scenario the rate of fire is around 1 shot/min.
The Russian 2S7 is bigger and weighs a staggering 46.5 ton, have a L/56.2 barrel which gives a V0 of 960 m/s and gives the 110 kg shell an impressive 37.5 km range. However, it only carries 8 rounds and can at best handle a rate of fire of 2.5 shots/min. 2S7 is 13 meters long and has a crew of seven.
These kinds of calibres are unreasonable for highly-mobile artillery that supports the combat units of a brigade, and are better suited to hammering fortifications.
Eastern countries also employ 122 mm. The most common vehicle is the 2S1 (122 PsH 74 in Finnish service) which fire a 21.7 kg shell out to 15.3 km from a L/36 barrel, it weighs 16 ton, has a crew of four, and carries 40 rounds.
A modernised version of the 2S1 is known as the 2S34 Khosta which sports a 120 mm gun/mortar with a range of 14 km. The same gun is found in the 2S31 Vena which carries 70 rounds and weighs 19.5 tons.
In Sweden we had the 12/80, a 120 mm version of Haubits 77. With a L/55 barrel it had the same range with load 2 that the L/38 Haubits 77 had as its maximum range.
Calibre 105 mm is something that usually has been found on the battalion level. An example of a modern system is Hawkeye which is based on the HMMWV. The weight is just 4.4 ton. With a L/27 barrel is has a range of 11.5 km with a 15 kg shell. According to one source 8 rounds are carried.
There are also long-ranged 105 mm systems. The Swedish turreted automatic 105/50 with L/54 barrel had a range of 20 km. It is especially interesting that a number of other countries still cling to and develop 120 mm-class guns. I will therefore make a comparison between 120 and 155 mm weapons when it comes to a few specifications I regard as critical for brigade artillery.
Range, less is more!
Upon a quick comparison 155 mm seems to have the edge when it comes to range. 15.3 km from a L/36 barrel compared to 24 km from an L/39 when comparing 2S1 and M109. However, 2S1 uses a rather modest 3.8 kg powder charge to reach a V0 of 680 m/s and 15.3 km. At the other end of the spectrum, Swedish 120 mm Tornautomatpjäs 9101 (12/70) uses a L/62 barrel to reach 27 km with a V0 of 880 m/s. The earlier mentioned 120 mm 9501 (12/80 Karin) can reach 21.1 km with charge no 2 with a V0 of 800 m/s. 155 mm guns with a 800 m/s V0 can reach around 22 km, meaning that the difference is rather small. 120 mm as a calibre has good ballistic properties. With a barrel length of around L/50 a 120 mm gun will use 5-6 kg and a 155 mm one 12-15 kg of powder to reach a V0 of 800 m/s. A 120 mm L/62 is also 60 cm shorter than a 155 mm L/52. In other words a rather small potential edge in range for the 155 mm is balanced against having a long barrel that’s still easily handled for the 120 mm.
Another aspect of the range question plays a major role in the discussion, and this is where less is more. The fact is that when the range approaches or pushes beyond 20 km, the shells will follow a trajectory that is so high, and spend such a long time airborne that the weather makes accuracy unacceptably poor. The reason is partly because it becomes hard to reach the desired effect without ranging shots and/or the need for additional rounds in target, and partly because the increased dispersion increases the danger for the friendly units one tries to support. Base bleed and rocket assisted projectiles (RAP) which are used to increase the ranges also further diminish accuracy and increase cost. To counter this increase in dispersion once the range is edging towards 40 km technical aids such as precision-guided rounds and course correcting fuzes are used. These are very expensive, and ill-suited to the massed fires required to support ground combat. Firing at ranges between 30 and 40 km also has other consequences. At least double the gas pressure and V0 close to 1,000 m/s leads to increased strain on the equipment and faster wear. My opinion is that if the laws of physics makes it a bad, or at the very least an expensive, idea to use supporting fires at ranges above 20 km, then we shouldn’t invest too much money and effort into such a capability for systems acquired to support ground combat. To reach 20+ km 120 mm is plenty enough.
Presume a fire mission of 24 155 mm rounds would be replaced by a single round with the same weight of just over 1,000 kg in the middle of the target area. It is obvious that the effect would be poor in the majority of the target area and unnecessary good close to the giant round. Ordinarily one strives to spread the effect evenly over the whole target area. Case in point being the use of submunitions. Before the Convention on Cluster Munitions there was even a project on introducing 120 mm mortar rounds with submunitions, and in Russia who doesn’t give a damn about the ban on submunitions their use is increasing. Against fortified targets heavier rounds do however maintain the edge.
In a comparison between a big bang and thousands of submunitions one can compare the weights of 24 rounds of 155 mm, 45 rounds of 120 mm, and 72 rounds of 105 mm. The superior effect would in this case come from 72 rounds of 105 mm. A good indication is that a Swedish fire mission of 24 120 mm mortar rounds is treated as the equal to 18 155 mm rounds. The weight of a mortar round is in fact more closely equal to that of a 105 mm howitzer round. The effect of a single 120 mm howitzer round matches very closely that of a 155 mm one. The issue is that one reaches further with a heavy round, but preferably would split it up in many smaller units when reaching the target area to get superior effect. As long as we uphold a ban on submunitions the importance of choosing a calibre that gives good effect in the target increases. Scientific advances also make it possible to fit a seeker in smaller rounds than before, though it would be difficult to get as good effect e.g. out of a 120 mm BONUS-round as out of a 155 mm one.
To compare the logistics footprint I make the assumption that 24 155 mm rounds equals 30 120 mm rounds when it comes to effect. A complete 155 mm round has a weight of around 60 kg, made up of a 45 kg shell and a 15 kg charge. Similarly, a complete 120 mm round weighs around 32 kg, of which 25 kg is the shell and 7 kg the charge. The fire mission of the 120 mm gun would then come in at two-thirds the total weight of the 155 mm fire mission. If you include a casing to allow for the automatic handling of the ammunition a complete 120 mm round comes in at approximately 40 kg, meaning the fire mission is just 83% of the weight of the 155 mm one. However, fixed ammunition require more space, and the 120 mm fire mission with fixed ammunition will take up approximately 20% more space. However, comparing against fixed 155 mm ammunition the latter will weigh 70% more and take up 40% more space. The benefit of fixed ammunition is that in the same way as with Bkan and 120/80 it is possible to have a higher degree of automation when firing and handling the rounds. This in turn leads to a higher rate of fire and better effect in target. The conclusion is that with fixed 120 mm ammunition you get a similar logistic footprint, but with a round that is more easy to handle and you will be able to get off more rounds which will give as good or better effect in target compared to 155 mm. In real terms, a full charge 120 mm round with a fixed casing will weigh less than 40 kg, and can easily be carried from vehicle to vehicle by a single soldier. A 155 mm round with a fixed casing will come in at 85 kg and will need two persons to carry it, not the least due to the uneven weight distribution. If an autoloader could use the kind of combustible casings that tank rounds use, it should be possible to shave a few additional kilograms of the 120 mm round.
Autoloading versus manual
To achieve good effect in target a high rate of fire is a good tool, and to reach a high rate of fire the ammunition and its handling plays a big role. 155 mm howitzers usually have a rate of fire that varies between 3 to 10 rounds per minute with separate loading ammunition. These are usually either completely manual or equipped with different kinds of automatic handling and loading aids. Some have the ability to fire off a few quick rounds, before settling in for a lower sustained rate of fire. E.g. Haubits 77A was able to fire three shots in less than ten seconds. This is possible as the charges are put in a casing, which allows for the use of a very quick vertically sliding breech block. The shell and the casing is then loaded with a hydraulic rammer. To fire really quickly fixed casings are needed. E.g. Bkan 1 has a technical rate of fire of 18 rounds/min. The 12/80 is another example albeit with 120 mm calibre. With an autoloader the 12/80 fires off 16 rounds/min. There are even faster Swedish guns. 120 mm anti-aircraft gun 4501 has a rate of fire of no less than 80 rounds/min. The 23 ton heavy gun carries 52 rounds.
Another Swedish rapid-firing gun, although in 105 mm, is the Strv 103. As far as I remember, the technical rate of fire is 26-27 rounds/min and the tank carries 50 rounds. To note is that the sole 155 mm field artillery piece amongst these was the Bkan 1. The reason behind this is, amongst other things, that the mechanism becomes large and heavy. It is also unable to bring along more than 14 rounds. This is likely one of the reasons why modern 155 mm guns almost universally have separate loading munitions. The second, and perhaps even more important issue, is that one wants to be able to set the charge size for each round, and not be limited to a pre-set number of each charge that is set already when the ammunition is manufactured. In 120 mm it should however be possible to benefit from the carefree handling of fixed ammunition and bring more rounds, without the rounds becoming overly large.
Autoloaders is however not an end in itself, except when it comes to the firing. As mentioned earlier, 120 mm is considerably easier to move by hand. This includes fixed case 120 mm ammunition, which thanks to its below 40 kg weight can be moved in the same way ammunition was replenished in Strv 103.
Will there be something else than 155 mm if we buy a new system?
I have a hard time believing that, 155 mm is in all essence even more standard than 7.62 mm. That is why I describe this as an unreasonable brigade artillery. If one would start from a clean sheet, it is however entirely possible that with the technological advances of today the conclusion would be that another calibre would be better suited for supporting the brigades. Perhaps based on some of the reasoning found above.
But we just have to accept that we do not begin with a blank sheet, instead there are several limiting factors that affect the outcome. At the same time, evident truths need to be questioned every now and then. E.g. the miniaturisation of electronics allow for ever smaller rounds to become “smart”. If the reasoning behind 155 mm was the need for precision guided munitions the choice of calibre could be reevaluated now. However, over time factors such as standardisation have become important and will lead to the continued use of 155 mm.
Are we in the West looking for the right capabilities?
As a short sidetrack to the discussion on calibre choice I would like to touch upon two topics that I believe are receiving too much attention: the race for range and extreme precision.
With each new gun there are new solutions to push the range out even further, from L/39 barrels to L/52 as the new standard, and now barrels out to L/58 are discussed even for guns such as the M777.
Base bleed, RAP, and ramjet projectiles are other ways of reaching further. It is easy to see the benefit of reaching longer, and easy to quantify range as a requirement or selling point, which is why it is often in the spotlight. But range threatens to become the “24 cm higher cabin” of the artillery, an extreme cost driver. Longer range also places indirect requirements on extreme accuracy, no longer is just “rather accurate” good enough. The technology behind the increased accuracy is and will continue to be expensive. This means that the ammunition used to fire far away and with high accuracy becomes too expensive to use for massed fires. The most extreme example is the 155 mm guns of the Zumwalt-class which were supposed to receive rounds capable of reaching 153 km. The price tag became close to 1,000,000 USD/round as opposed to the planned 35,000 USD. The contract was revoked and the destroyers now lack a suitable round for their guns.
There need to be an analysis regarding the missions of individual systems. For a multitool, which is the role one can say that the Haubits 08 has been forced into, long range is a must. If it is a battalion-level asset, the conclusion might be that the 8 km range of a mortar is enough. If the mission is to support the fighting battalions of a brigade, the requirements need to be in sync with those demands, and not necessarily with those of the multitool. Was the reasoning behind the 150 km range of the Zumwalt’s 155 mm guns really correct? Should one have opted for another system if 150 km range was demanded?
The quest for accuracy partly comes from the increased range, but also from some kind of engineering bewitchment for perfection. Accuracy is very nice when the enemy headquarters is located or when the enemy has put their fighting positions close to a hospital. But at the end of the day, artillery is an area effect weapon, and to achieve effect it is enough to hit the target area instead of aiming for the bullseye with every round. I am worried that we in the West is forgetting this. I don’t know how many times I’ve heard “Isn’t it jolly good to have better accuracy, that we can get the same effect with fewer rounds.” I have tried to explain that it is enough to be in the right area and that it is more important to be able to fire large volumes in many places, which increases the odds that the enemy will be suppressed in many different spots. Often the fire mission is based on an estimate on the enemy and the terrain, and not on an observation. If one can see the enemy both we and the enemy can use direct fire, and it is the losses that causes which we wish to avoid. Why then aim for a few expensive bullseyes and completely overlook massed fires? Making this case is often like talking to the wall. I will however persist, gutta cavat lapidem.