Solothurn S18-100 S18-1000 and S18-1100 anti-tank rifle (Switzerland)

Solothurn S18-100 anti-tank rifle.

Solothurn S18-1100 anti-tank rifle; it was externally similar to the S18-1000, and the main difference was the select-fire capability of the S18-1100.

	Solothurn S18-100	Solothurn S18-1000
Type / action	semi-automatic, recoil operated
Caliber	20x105B	20x138B
Weight unloaded	40 kg	51.7 kg
Length	1760 mm	2170 mm
Barrel length	930 mm	1447 mm
Magazine capacity	10 rounds	5 or 10 rounds
Armor penetration (Range / Angle / Penetration)	100 m / 90o / 35 mm 300 m / 90o / 27 mm	100 m / 90o / 40 mm 300 m / 90o / 35 mm

 Small Swiss arms-making company Solothurn Waffenfabrik AG emerged on the world markets during late 1920s, when it was purchased by huge German military contractor Rheinmetall Borsig AG. The Solothurn factory became an off-shore R&D and sales front-end for Rheinmetall, which was at the timeseverely limited in its military activities under treaty of Versaiiles. Using experience and ideas of German designers, Solothurn factory quickly developed a number of innovative small arms, ranging from submachine guns and up to large-caliber anti-tank rifles, which in certain respects were closer to artillery pieces rather than small arms. The Solothurn S18-100 was the first in line of large-caliber anti-tank rifles, developed by Solothurn during early 1930s. This was a massive weapon, which could be carried by the single soldier for a short time, and certainly not suited for firing it off-hands. Nevertheless, it was considered as antitank rifle rahher than cannon. It was offered for export sales, and a small number of  Solothurn S18-100 anti-tank rifles were sold to various European countries, such as Hungary or Finland. Later on, Solothurn engineers decided to improve performance of the gun, and redesigned it to fire more powerful 20x138B ammunition, which was also used in German FlaK (Anti-Aircraft) guns such as FlaK 30 and FlaK 38. This version was offered to intersted buyers as  Solothurn S18-1000 anti-tank rifle; a select-fire version of the  Solothurn S18-100 anti-tank rifle was offered as S18-1100 "Universalwaffe" (universal weapon), as it was intened for use against tanks from integral bipod, firing semi-auto, and as anti-aircraft gun (firing in bursts) from special AA mount. This version also found some buyers, including Italy, Netherlands and Switzerland. Few of the S18-1100 guns also were used by German army during WW2 as PzB-41(s). Overall, Solothurn guns looked like formidable weapons which could deal with variety of targets, using AP or fragmentation loads, but by the 1942 its armor penetration was insufficient to deal with Soviet T-34 tanks. These rifles also were overly heavy (at least, by standards of the foot infantry of the time), complicated and quite expensive.

Solothurn S18-100 anti-tank rifle is semi-automatic weapon which uses short recoil principle to operate its action. The barrel is locked to the bolt using rotary nut, attached to the barrel breach. This nut has series of lugs on its inner surface, which engage cuts made on the bolt heads. Upon recoil the nut is forced to rotate and thus unlocks the bolt, allowing it to recoil freely once the barel recoil is arrested by the buffer. Upon bolt recoil, a spent case is extracted and ejected. Once bolt recoil cycle is complete, it is driven forward by the spring, loading, chambering and locking the fresh cartridge. The feed is from detachable box magazines, which are insrtted horizontally from the left. The barrel was equipped with muzzle brake to decrease heavy recoil. Weapon is fitted with adjustable folding bipod under the barrel jacket, and a folding monopod under the butt. Solothurn S18-100 anti-tank rifle was equipped with iron sights, adjustable for range between 100 and 1500 meters, and an optional 2.5X telescopic sight can be installed for more accurate fire.
The Solothurn S18-1000 anti-tank rifle was essentially similar to the S18-100, but it used longer and more powerful round, and thus was of somewhat larger dimensions and weight. It has longer barrel with more efefctive muzzle brake.