Solothurn S18-1000: The Pinnacle of Anti-Tank Rifles

Among all the antitank rifles developed between the World Wars, the highest quality and most sophisticated was the Solothurn S18-1000. It fires the 20x138B cartridge which was also used in the Finnish Lahti L-39 and the German 20mm Flak guns, and it does so using a semiautomatic action and an 8-round box magazine. It is a short-recoil system, with a rotating bolt rather similar to that of the MG-34 machine gun.

The recoil-operated action of the Solothurn helps dampen its recoil more than the Lahti, and is definitely a more comfortable gun to shoot. The Solothurn is equipped with both iron sights and an optical sight (we used the irons in this shooting, because the rubber eye cup on the scope is fairly hard and brittle on this example). Remarkably for its 100+ pound weight, the gun definitely jumps back a few inches when fired unless one has firmly sunk the bipod feet into the earth. However, the recoil force is really more of a push than a sharp impact, and combined with the large surface area of the shoulder pad it is not at all a bad experience.

A number of different countries bought the S18-1000 (and many others bought the smaller S18-100), including the Italians and Hungarians. The only combat account I was able to find was from a Dutch antitank gun team that used one to successfully engage several German armored cars during the invasion of the Netherlands in 1940.


  1. At least the gun is not as rare, heavy, or as weird as the Type 97 anti-tank rifle, which evolved into a flak cannon and bomber turret gun. How the Imperial Japanese Army got the cannon into a bomber mount with little complaining from the crew is beyond me.

    • “How the Imperial Japanese Army got the cannon into a bomber mount with little complaining from the crew is beyond me.”
      You probably mean Ho-1 and Ho-3 guns. Increase of caliber during World War II in aviation gun was logical effect of introducing more and more durable aeroplanes.
      Though Ho-1 and Ho-3 was not considering to be best 20 mm aviation autocannon by Japanese, as they developed Ho-5 autocannon, which has higher Rate-Of-Fire, it also 20 mm but for smaller cartridge (Ho-1 and Ho-3: 20×125, 127 g HE @ 820 m/s, Ho-5: 20×95, ~82 g @ 735 m/s). Ho-1 and Ho-3 fired 300-400 rpm, when Ho-5 in free (non-synchronous) version 700 to 850 rpm, depending on version.
      Trend to promote slower bullets allowing creating lighter aviation weapons rather than faster, can be also observed in other countries in that era.
      For example in Soviet Union step from VYa-23 autocannon (23×152 cartridge) to NS-23 autocannon (23×115 cartridge). Such action was effect of conclusion that, against aeroplanes HE filler matters more than ballistic and such guns are fired rather on close distance.

  2. Dang, Ian, in that slow motion shot from behind and to your right, you can see the recoil “push” move through your hair!
    As to actually shooting the thing: I’m pleased to see SOMEONE is getting to check off items on MY bucket list. :/

  3. Super video as always. Where is this particular gun from? It’s a bit confusing. On the magasincover it clearly says ” 20 mm PVKAN M/39″. That sounds like a swedish designation. (PanserVernKANon). But the swedish PVKAN M/39 was a 37 mm weapon.

  4. And to think, around 1960, when this was still a free country, you could purchase the Solothurn for less than $200 (and it’s ammo) Good to see you channeling Henry Bowman, Ian.

  5. The Italians used the S18-1000 and the select fire S18-1100 fairly extensively in North Africa. Quite likely they saw their most extensive combat use in Italian hands. During the first year of the war in NA the Solothurn was a fairly rare but highly respected weapon, which the Italians mounted for example on the L3/35 light tanks as a field expedient. It could penetrate the armor of the British Mk VI light tank from any angle and the side armor of early British cruiser tanks such as the Crusaders. Armored cars were widely used in North Africa and the Solothurns were effective against them as well.

    Later the Italians got more Solothurns, but by that time the British started to receive more heavily armored tanks such as US built Grants and Shermans, and the Mk VI light tanks were phased out, so the usefulness of the gun diminished. The S18-1100 was mounted on some vehicles, but the Italians did not like it very much because of the high dispersion on full auto, and preferred to use 20mm Breda AA guns, which fired the same cartridge. The Solothurn was much more compact, however, and could be mounted on places where the AA guns would not fit. On a ground mount the S18-1100 was of course not usable on full auto and most if not all of them were mounted on vehicles.

    • Now, I am wondering if Swiss forces considered or tested Solothurn S18-1000?
      Even if did happen, they decided to introduce 24 mm Tankbüchse 41 for role of AT rifle, photos:
      It was self-loading weapon with magazine capacity equal 6. Interestingly it was derived from fortress gun, which itself was derived from tank gun (main weapon of Panzerwagen 39 (Praga) as 24 mm Pzw-Kan 38). It might be used with wheels or tripod of adjustable height (see photos in link)

      • Perhaps the Swiss wanted a more potent weapon than the Solothurn. The 24mm Tb 41 is even more a missing link between an anti-tank rifle and anti-tank gun that the 20mm weapons, since it could be used either on a tripod or wheeled AT gun mount. I have found no armor penetration numbers for it, but the general ballistic performance was very similar to the French 25mm SA Mle 1934.

  6. Ian,
    What is the cylindrical component on left side under the sight? Look like an optic but didn’t appear to have a safe eye relief when you were shooting it. Thanks!

  7. This many comments and nobody said anything about the huge role the Solothurn S18-1000 rifle played in the classic gun-culture novel “Unintended Consequences” by John Ross? It was protagonist Henry Bowman’s favorite rifle, the last rifle Henry shot with his father before the elder Bowman died of cancer. And, it was Henry’s weapon of choice when the bad guys from ATF came calling to kill him and his friend. Ross even described the process of reloading ammo for it.

    What a rifle!

      • It works very well against choppers, especially the black unmarked UN / US federal government kind.

        Joking aside, on full auto and mounted on a vehicle the S18-1100 would probably work okay against low and slow flying aircraft like a helicopter. It was not provided with an AA sight to my knowledge, but tracer ammunition was available.

        • This leads to rekindling thought on usefulness of similar weapon for today’s use. I did actually think in past of something in 25mm range and to improve mobility to be based on light carriage combined with spades. It could be pulled by any of those small ATVs. Surely, it would not be of use against tanks (unless you manage to neutralise their sights), but low hovering helicopters (at time of dropping troops and cargo) and APCs, perhaps. It would be worth of comparison between this kind of device vs manpads; pros and cons.

          • “(…)25mm range and to improve mobility to be based on light carriage combined with spades(…)could be pulled by any of those small ATVs”
            ZU-23-2 seems to fit your description:
            it was often towed by GAZ-69 vehicles (4×4, 55 hp engines).

          • “this kind of device vs manpads; pros and cons”
            AA gun must have mount providing stability, providing also fast train rate and elevation/depression rate. Sights also are essential to hitting anything. It would be much different, as it would be able to fire several smaller projectiles rather than typical to MANPAD single projectile (however there existed unguided multiple-launch shoulder-fired AA weapon, see Soviet project «Колос»:
            possibly inspired by German Luftfaust, which is shown at 2nd photo from top)

          • @Daweo

            You are right with ZSU-2, but this system is quite heavy and cumbersome although it can be made mobile in record time under one minute. Its main purpose is air-defense against fast moving targets in upper trajectory. There was one time a common Czech and Slovak project to upgrade it by implementing better sights, targeting processors and fast acting servo-drives. It remained in prototypes afaik. Name of the project was Vlara after river on border between both countries.

            What I have on mind is something substantially lighter (around 350kg with mount) and smaller with single barrel, dual ammunition drum feed and advanced opto-electronics. It does not have ambition to take on fighter planes.

            When comes to MANPADS they have two disadvantages. First is cost of their warhead and second is smoke trail they are leaving. To use them properly it must be one shot and one kill and move out quickly to new position. Other than that they are phenomenal. I am talking about both ground and air defense types.

          • @Daweo – cont’d
            To add to my conceptual thought (you must be wondering about that low projected weight) I can only say that the core is in rather ‘tricky’ dynamic solution (rifle itself should be at around 80kg). Shame we live so far apart…. you could enter lots of useful input.

          • “rifle itself should be at around 80kg”
            Then AM-23 might be good starting point:
            it weights [gun itself] 43 kg (but that is aviation weapon, ground version might require heavier parts, as there would not be air-flow cooling this weapon), also it fire 23 mm bullet as ZU-23-2, but use smaller cartridge – 23×115 mm against 23×152 mm of ZU-23-2, so it has muzzle velocity 690-710 m/s against 970 m/s. It has Rate-of-Fire of 1200 rpm, which is smaller than ZU-23-2 overall (2000 rpm), but better than single barrel of ZU-23-2. AM-23 is belt-fed weapon, it might be fed from left or right side, cases ejection direction is downward.
            Length 1467 mm (1000 mm-barrel version), width 166 mm, height 175 mm.
            As you might see from its name it was co-designed by Makarov, this same man that designed Makarov automatic pistol, 9K111 (NATO parlance: AT-4 Spigot) AT weapon, 9K111-1 (NATO parlance: AT-5 Spandrel) AT weapon.

          • @Daweo – cont 2

            AM-23 gun is certainly a masterpiece; never seen it before myself. So is its complexity and cost. Since it is designed for air use it is probably justifiable. However, I’d not go to such extent for ground use weapon.

          • “never seen it before myself”
            Then you might found interesting some drawings of АМ-23 available here:
            First part is about А-12,7 (earlier design by Afanasev) which has natural cyclic Rate-of-Fire of 1500 rpm. However you might also found source claiming 1000 rpm or so, which is also true – Rate-Of-Fire was artificially lowered, as metallurgy was unable to provide durable enough barrels (barrel liners) to give required service life. А-12,7 was adopted to service in September 1953.
            Anyway to 23 mm weapon: according to article there were parallel design, one for 23×115 weapon (ТКБ-495, which become АМ-23 later) and one for 23×152 weapon (ТКБ-494, rate of fire: 1100 rpm)

      • As one character in the novel commented, you don’t need much more than a standard hunting rifle to give most helicopters a lot of trouble.

        For that matter, crosswinds and trees are bad news, too. Plus wires. LOTA (Loss Of Tailrotor Authority) does not love you.



  8. I’ve been waiting for a bit before someone comes with felt recoil observed by Ian related to caliber AND mainly, its operating concept. How is it possible that this oversized weapon (by caliber) can be safely handled while firing from shoulder? Is the operating concept somehow related to it? I could continue but give it a break instead and wait for others to pick up the line.

    Seemingly non-relating designs such as Browning, Japanese Ho line of guns and perhaps Italian SAFAT were also recoil operated.

    At the end one side observation: I am sorry for female gunner at last minute of the footage.

    • After some search in order to find out details of operating mechanism I found one page in French which included picture originally from Russian source. When attempting to enlarge it became blurry, so nothing’s there (maybe Daweo can try more successfully in Russian sources).

      Mr. Popenker’s page says that the barrel includes rotary nut/sleeve which turns during recoil which in turn unlocks bolt. There is no mention of means to decelerate barrel (other than muzzle break) in dynamic sense as in Browning fifty. There is decent shock absorber built into buttplate to tame energy of rear moving action. The housing on top of gun contains return spring. It appears to be efficient layout, but not overly inventive in sense of energy management. It was showcased couple of years back on FW in form of shooting display.

      • “(…)included picture originally from Russian source. When attempting to enlarge it became blurry(..>)”
        Well, I know about drawing for S18-100 AT rifle (100 NOT 1100), however maybe it will be helpful:
        For further data, considering that Solothurn made these weapons for export, I would suggest searching for patents.

        • Thank you kindly Daweo,

          this is the same picture but lot more legible. And to my satisfaction…. No.14 is “uskoryayushchiy richag” – accelerator. Now I should go and modify my previous comment about energy management. And this is likely reason behind low sensed recoil.
          Got it!

    • “How is it possible that this oversized weapon (by caliber) can be safely handled while firing from shoulder?”
      From point of view of firing powerful cartridge AND not breaking bones or doing other harm to wielder I think one weapon might be interested. SR Model 14 for 12,7×99 cartridge.
      Now I must say that I am not very contented with giving link for Russian-language site for Australian-build gun, but was unable to get competitive site in English.
      Anyway here it is:
      Photos from top to bottom:
      – SR Model 2
      – SR Model 2, partially disassembled
      – SR Model 5, fully disassembled
      – aviation Model 14 (upper) compared to Browning M2 /notice shorter length, despite both firing SAME cartridge – 12,7×99/
      – infantry SR Model 14 on American-developed tripod
      – Robinson himself firing technology demonstrator for SR Model 14
      – firing SR Model 14, infantry variant
      .50 caliber Robinson machine guns was Constant Reaction Principle weapon (subclass of short-recoil), SR Model 14 mass was 15,4 kg (aviation version)

      • I am somehow familiar with Robinson’s experiments (moving equal and opposite mass against action) but afaik it did not turn out into serially manufactured weapons.

        Within constrains of soldier’s endurance were and still are produced systems which use is questionable. I recall in mid 80s Oerlikon created “take-down” 25mm canon which was based on KBB ammunition. It was supposed to be carried disassembled into components on backs of soldiers within team. It did not take off and project was shelved.

        • “it did not turn out into serially manufactured weapons”
          Yes, after ending of war, interest in .50″ aircraft machine gun dwindled and disappeared. Also availability of large numbers of US-made .50″ machine guns was counterproductive to introduction of new weapon of that class. Similar fate to French MAC-58:

  9. Having read the above fascinating discussion about creating a large calibre AA (or rather Anti Helicopter) gun, the British Army thought about this in the 70’s, and came up with the SCAT mount combining 2 GPMG’s (FN MAGS). SCAT stood for Should Cost A Tenner, and was abandoned due to cost!

    I’m obviously using the tread to shoot off an anecdote, but there is a fair pint behind it. Most modern armies have always had a need for long range anti-materiel rifles; but an awful lot of them did without due to fashion. The fact that the USA found itself fighting in deserts and mountains changed the fashion; but all of the development is in sniping weapons; and there are always private developments in sniping because of hunting.

    I can see no fashion trend to develop better ‘small’ AA or AH guns. The may be plenty of people wanting to shot down police helicopters, but no gun company is going to spend money developing one, just for a civilian market; and until a military express an interest they are never like to do so.

  10. Awsome!!! My da picked one up in the 50’s and registered it in ’68. Along with several mags and the spare parts Kit. Is ammo available???

  11. Denny, you nailed it and pointed out an issue that is commonly gotten wrong by bloggers, articles and videos. The Solothurn most certainly does not have a rotating bolt. At least one of Ians video has him saying that the huge 8 lugged bolt rotates but it does not.

    The lugs on the bolt both top and bottom are machined into the bolt head which is in turn machined from the body of the bolt carrier and they are all one piece. The bolt slips into a rotating locking sleeve when it pushes the round into the chamber. The locking sleeve system is the basis of the patent filed by Louis Stange for the Solothurn light machinegun of the late 20s. The locking system was also used in the MG15 and I believe the MG17 machineguns used by the Germans as aircraft guns. The removable barrel locks into the sleeve on installation. The sleeve recoils with the barrel and a cam rotates the internal sleeve that locks the bolt to the barrel. On recoil the sleeve releases the bolt which is accelerated to the rear by a a lever which looks much like the accelerator for the M1919 browning machinegun. This helps separate the bolt and barrel.

    The mainspring is a large diameter piece that is the length of the main receiver. It has inside it a smaller spring wound in the opposite direction to prevent binding and jamming. The two springs together slow the bolt enough to prevent it from hitting the backplate when set up properly. Using the single hole muzzle brake with armor piercing ammo will overcome the springs but this is not a situation normally encountered. A single port brake, 3 port brake and 5 port brake are supplied for the gun to allow for variation in projectile weight. AA projos weigh about 1400 gr while AP is about 2300 so the energy required for braking the movement of the barrel is considerably different. There is other ammunition with projectile weights in between those two and they are operated with the 3 port brake.

    Much info in articles and videos is supplied by people who have never actually seen the real guns so the number of mistakes and misconceptions is high. Ian at least fired the gun and it is not possible to see the bolt locking up from outside so mistaking the rotating bolt for reality isn’t so obvious. To those who have disassembled and worked on the guns however it is really clear.


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