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 semiautomatics 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 optic 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 it really more of a push that 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 form a Dutch antitank gun team that used one to successfully engage several German armored cars during the invasion of the Netherlands in 1940.
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