Artillery calibres and concepts


The most common artillery (gun) calibres are nowadays in the 105...155 mm range. Bigger guns largely fell out of favour due to aircraft bombs taking over their roles and smaller guns largely fell out of favour because direct artillery fires lost importance post-1914.


75 mm was considered the minimum calibre for a high explosive (HE) round to be really good at supporting infantry with direct fires. Infantry support tanks of late 1930's received guns of such a calibre, albeit wartime experiences led to the introduction of bigger calibres (up to 152 mm plus one freak design) for that role.

75 mm infantry gun, for supporting infantry

75 mm calibre guns had often a high muzzle velocity, which gave them a secondary anti-tank capability. This also allowed for a little better ranges than the common 105 mm howitzers of the time had. Their indirect fires usefulness was hampered by the small explosion signature (bang, smoke, dust) of their 75 mm HE shells, though. It was difficult to observe the explosions with sound ranging or visual observation from afar. There's no correction of fires without feedback from observers, thus poor accuracy.

105 mm howitzer HE was an indirect fires sweet spot for a long time, and probably still is. The Russian/Soviet 122 mm calibre was a bit more powerful and the British 87.6 mm (25 pdr) calibre was fairly close as well, but 105 mm was understood to be very efficient for fragmentation effect and suppression. 150...155 mm HE shells were more powerful individually, but covered less area with fragmentation effect or suppression effect than did the 105 mm HE - pound for pound. 105 mm HE also enjoyed a reputation for being more capable at shooting danger close (at targets very close to friendlies), albeit this is a negligible difference when the guns don't have a tight dispersion.

I've seen tables and lessons learned about 105 and 150 mm howitzers use in WW2 and the conclusion from the different quantities of munitions needed for certain effects was simple: You did not need more 105 mm munitions mass for the purpose than 150 mm munitions mass. The calibres were largely substitutes for effects. You needed more 105 mm shells for the job than 150 mm shells, but a 105 mm shell weighs about 17 kg, and a 150 mm shell weighed about 40 kg. 105 mm howitzers also had a little higher burst rate of fire (fires in first minute before the barrel is hot and rate of fire has to match how quickly the barrel cools down). 150 mm howitzers had some manpower efficiency and sustained firepower advantages (both calibres sustained about the same rate of fire).

150...155 mm had two big advantages over 105 mm  during the world wars, though. One, it was more capable of piercing overhead cover and the roofs of field fortification bunkers (several layers of wooden logs plus earth, supported by wooden logs). This is where the 150...155 mm success came from; Germans tested field fortifications around 1900 and came to the conclusion that a 150 mm shell was required to penetrate a field bunker (but keep in mind howitzers had poor muzzle velocities at that time). Such intent to destroy almost entire sections or platoons in a field bunker led to a mass employment of heavy howitzers (and even heavier artillery) in the Great War a.k.a. First World War.

Two, larger calibres are also more efficient for long range (better ratio of kinetic energy to drag), and howitzers grew into high velocity (and thus long range) guns especially after the Cold War. Today's 155 mm L/52 howitzers have ballistics that rival late WW2 high-performance cannons of about the same calibre.

modern 155 mm L/52:  43...43.5 kg shell, approx. 945 m/s with maximum charges

150 mm Type 5 (1945): 41 kg shell, 930 m/s

155 mm is thus superior to 105...122 mm for two purposes; destructive fires on field fortifications and long range fires. The latter were a nice niche for dumb shells in the 1990's till 00's, but it's obvious that guided rockets are more suitable for it because it's much easier to give guidance to a rocket than to an abruptly launched (electronics need be hardened to this shock) projectile. Shells are normally spin-stabilised, which prohibits normal steering by rudders. Guided 155 mm projectiles are fin-stabilised and thus differ only in the mode of acceleration from rockets. The barrel restricts the calibre, so using rockets launched from pods makes much more sense for long range fires.

Which leaves us with the destructive fires on field fortifications (and rare effects on armoured vehicles) for the 155 m calibre. So let's talk about what I meant with "destructive fires".

There are harassing fires, suppressive fires, neutralising fires and destructive fires.

Harassing fires are almost always bollocks, waste of munitions and at times plain war crimes (if shot at the wrong coordinates).

Suppressive fires are more intense and shall limit hostile activities, especially how much hostiles dare to move or shoot. It's not so effective at limiting how much they observe and report. Suppressive fires may make sense to support (= protect) exposed (usually that's = moving) friendly forces.

Neutralising fires are more intense than suppressive fires and shall render hostiles combat ineffective through psychological effects (up to shell shock). The targeted troops may have a few per cent losses of personnel and material through blast or fragments, but that's not what matters. Properly done neutralising fires allow almost none of the targeted hostiles to be effective shooters for minutes after the end of the neutralising fires. Neutralising fires make much sense when friendly troops assault and take the targeted position soon after the neutralising fires ceased. Neutralising fires are thus most important for manoeuvring forces and for attacks with limited objectives (by forces of the line).

Destructive fires are not necessarily more intense, but they require much more munitions (or precise knowledge of hostile positions and great precision at firing at them with powerful-enough munitions). This is wasteful for manoeuvring forces such as a armoured formation on a rampage after breaking through a frontline. Destructive fires usually take more time and more munitions than neutralising fires (and may make the ground less trafficable by cratering), which is really bad for a manoeuvre force (force of exploitation).

also see FM 3-09 pages 3-25 and 3-26 if in doubt

Coming back to the forces of the line and forces of exploitation distinction, we can see that the middle calibre group of 100...105 (maybe up to 122) mm calibre was very suitable to support forces of exploitation.

The same calibre group was also very suitable for forces of the line most of the time. The two exceptions were long range fires (especially in WWI), which could be left to levels above divisions and destructive fires. Bigger calibres for destructive fires were not essential when breakthrough (using artillery mostly for neutralisation of the assaulted positions and suppression of other possibly intervening positions) was possible. The possibility of breakthrough depends more on morale and competence than on equipment, and some armies had this competence from late 1917 onwards.

The actual niche for 150...155 mm calibres was thus attrition through destructive fires along the frontline. This was likely the main reason for why 150...155 mm "heavy" howitzers were used by most European and American infantry divisions of WW2 and also considered essential during WW1. Their popularity also stemmed a bit from (slightly) better ranges than 105 mm had and subjective preference of bigger bangs. The weights particularly of WW2 howitzers were troublesome if not intolerable for horse draft, though.

152...155 mm calibre munitions are also more efficient for the deployment of cluster submunition types than 105 mm, but this advantage is now gone due to the widely followed cluster munitions ban.

The smaller size of 105 mm guns and their easy integration into wheeled motor vehicles (such as 6x6 or 8x8 lorries, which allows for a fragmentation and bullet protection, 360° turret, 85° maximum elevation, whole crew onboard, RCWS and lots of munitions onboard) as well as their danger close qualities position them as rivals of 120 mm mortars. Meanwhile, their muzzle velocity allows their use as heavy anti-air gun against easy targets (such as multicopters) with appropriate proximity or electronic time fuses. Their much better range (and dispersion at range) than 120 mm mortars opens up opportunities for covering larger areas, including assisting neighbouring units by massing fires.


So long story short; 105 mm is still a great calibre. 155 mm is more impressive and can do almost all the same jobs (except danger close shots), but 155 mm is far from a necessity. A mix of 105 mm howitzers and precision-guided rockets of long range (as much maximum range as target detection range) would do the artillery job just fine and render mortars unnecessary. 105 mm is less demanding regarding platforms, purchase costs and just generally lends itself better to the battalion battlegroup organic fires role (and to small brigades).








  1. Artillery ammo consumption from russian manual (Правила стрельбы и управления огнем).

    1. https://postimg.cc/zy2kSKM3

  2. With the fallback to an industrial style of war in Ukraine, 105mm rounds also require a fraction of resources to build compared to 155mm. Presumably they're also cheaper.

  3. After reading the closing remark in this article, as well as other ones on your blog, I get the impression that mortars are in this weird spot where they don't really do anything well anymore.

    First all of all, all traditional mortars are extremely susceptible to counter-fire because of how easy it is to monitor their low speed, fin-stabilization ammunition that they fire. Using traditional infantry mortars is a death sentence because of how slow it is to pack up and move from a firing position before counter-fire would vaporize them. The solution to this problem is to motorize the mortar but that of course greatly increases costs. There are silent spigot mortars that do not have this problem of counter-battery fire but they have small payloads which makes them a squad/platoon weapon for the most part; only the French really use them in any capacity and in a squad role (51mm LGI Mle F1).

    Secondly, the mortar calibre's in use are poor choices. The typical 51/60mm squad/platoon/company mortars are underpowered (Finland did studies on them and found them lacking)
    and had their lunch eaten by 30/40mm UBGLs/AGLs (for example the Canadian government stated that UBGLs/AGLs offer the same capabilities as 60mm mortars). The 81/82mm company/battalion
    mortar is far more powerful than a 60mm mortar but then you burden your infantry with an extremely heavy field piece (if you are stupid enough to move it around with infantry) that is logistically heavy and requires a large crew and a vehicle to operate; at that point you might as well just use a 120mm mortar. Finally, you get to the 120mm mortar which seems to be the best mortar calibre in use but then suffers from another problem with countries turning their 120mm mortars into expensive 120mm gun-mortars which is a role that could be done with 105mm/122mm howitzers anyway because a lot of modern howitzers have 75° elevation which is pretty close to most mortars 85° elevation.

    Finally, if more countries were open to adopting IFVs/AFVs with high calibre and high elevation guns (instead of smaller calibre auto-cannons) then that would fill in any gaps created by using a mix of AGLs/UBGLs and high elevation howitzers. The BMP3's 60° 100mm gun was an excellent idea (that was poorly implemented) that came from the Soviet's experience in Afghanistan's mountains while the 42° 105mm Cockerill turret offers something similar.

    1. Ordinary quality 120 mm mortars and ordinary quality 120 mm mortar munitions require much less capability and budget to produce than artillery, so I suppose their utility for poor country armed forces is obvious.
      Poor countries would still do very well having 120 mm mortars for infantry battalion fire support and cheap 122 mm gun-howitzers in main effort artillery regiment(s).

    2. I 100% agree as it seems like traditional 120mm mortars make the most sense out of all the choices for mortars because they are cheap(er), add massive indirect firepower to an infantry battalion, have the similar logistical demands as 81/82mm mortars, and they are properly attached to a vehicle. The downsides is counter-battery fire as mentioned above but if the 120mm is being towed by literally anything with a motor then that can be mitigated to extent unlike masochists who think infantry should hump a 81/82mm mortar around.

      Our conversation maybe explains why the Soviets never bothered with mortars in the squad/platoon/company level and only used them at the battalion level at the end of the Cold War (and when they did use them they used mainly 120mm mortars or 82mm auto-mortars).

  4. Your suggestions are in line with what China is currently doing.
    They use 122 mm for most tasks and they are at lower units. 155 mm is lower in numbers and is used for counter-battery and other long range engagements. Or when heavy fire power is needed. For direct fire, they have a lot of 105 mm on many different vehicles.

    For rockets, they almost completely eliminated 220 mm. We know some of the launchers can be loaded with 220 mm rockets but we haven't seen it happening for years. They had both guided and unguided 300 mm which are being replaced with 370 mm. These 370 mm rockets can reach Taiwan from the mainland. There are also 750 mm rockets in limited numbers for very hard targets. The launcher for 370 mm can be loaded with 300, 370 and 750 mm rockets. Most (all?) 370 mm is guided so the use is more Western-like rather than Russian-like.

    To sum up until here, they use 105 mm for direct fires and 122 mm for common indirect fires. The 155 mm is common too for the reasons you wrote and large rockets are used for precision engagements.

    Now the differences:

    They have a lot of 140 mm rockets. These are used for prompt destruction of area targets. China believes massing gun artillery is both too effort intensive and uses too many assets.

    They have significant amounts of 120 mm mortars and gun-mortars. These have been self-propelled since the early 2000s. I am not sure why they have them. It seems the firepower they offer at low weight and price was found attractive.

    1. Thinking about it, their high-pressure 105 is derived from the British L7 gun. So it is not appropriate for howitzer use. They would have to introduce a whole new level of howitzers and a new caliber. And a high elevation 122 mm would definitely not fit most vehicles. In this context 120 mm self-propelled gun-mortars/mortars do make sense.

    2. The PLA uses 107 and 130 mm short range MRLs, no 140 mm MRLs.

    3. Oops. My mind went to the Grad.
      107 mm is mostly retired. We only saw it for a few times recently. And it was all mountain units.

    4. Looks like too much variety too me. If we count the 107 mm too, that is 5 different rocket calibers (107, 122, 300, 370, 750) 3 different mortar calibers (60, 82, 120) 2 different howitzer calibers (122, 155) and 2 different gun calibers (105, 125). That's a lot. AFAIK they also have a lot of recoilless rifles, grenade launchers, etc...
      I see a force of low mobility and high logistical needs there. And I would like to learn how they distribure such a variety of equipment. Extra firepower is not always good.

  5. What about using 155mm for longer-range guided munitions?

    1. As mentioned, restricted in diameter, huge launch shock requires more hardenning of electronics than with rockets, range inferior to rockets, needs fin stabilization anyway.
      Rockets make more sense for longer ranges precision fires.

  6. Just thought I would share this article as it is related:

    Pretty fascinating that the 105mm artillery systems and the more mobile 152/155mm wheel systems are doing better from a survivability perspective compared to the heavy, tracked and autoloading 152/155mm systems (something this blog discussed under the article "Army luxuries").