As the books are hard to obtain, I will share my latest notes on Schüler:
The name Schüler is well known in the German arms industry. However, the most well-known Schüler’s were those from a family associated with the SCHÜLER WAFFENFABRIK.
Friedrich Wilhelm Schüler (the son of the master stockmaker Ernst Friedrich Schüler) established a Rifle factory in Suhl in 1835. He died a few years later and the company was taken over in 1850 by his younger brother, August Gottlieb Schüler. From then it was known as the AUGUST SCHÜLER WAFFENFABRIK. This was owned by both August Schüler and his other brother Oscar.
In the 19th century several patents were registered for Schüler including:
9591 : 08 Nov 1879 : F Schüler : Einfetter (??) for felt plugs
57117 : 1891 pistol designs
Around 1900, August’s son Richard Schüler (1879-1965) began working for the company.
At least as early as 1904, Richard Schüler (started to develop powerful large bore cartridges especially for the German colonies in Africa and for the lucrative export markets. The first was the 11,2 x 60 Schüler, which was based on the 11,15x60R Mauser case. D.R.G.M. 239127 was issued for the 11.2x60 on 31 Oct 1904. This patent for August (Richard ?) Schüler was in relation to the smaller rebated rim diameter of the case. The advantage was in being able to use large volume cartridge cases in standard systems with normal M98 Mauser extractor. Schüler seems to have liked the rebated rim case, as the three rimless calibers are all of this type.
In 1906/07 he designed a much more powerful and improved version, the 11,2x72 Schüler, which was to become a popular German big game cartridges, on a par with the later developed .416 Rigby. Like practically all other contemporary Riflemakers, Schüler preferred the very strong Mauser Mod. 98 action for his bolt action rifles. His cartridge designs were based on the utilization of this action. The Schüler designed cartridges were generally all of 11mm caliber and above but in the late 30s, smaller calibers may have been used (see 6.5x68 : W59). Note that there is also a 8x25 Schüler Gas Pistol.
Richard received a patent again in 1906 for the Schüler “Reform” pistol.
By 1909 a rimmed 11.2x72R had been produced. Richard developed his Herkules Verschluss in 1909. Richard like many of his peers became involved in developing proprietary high power express ammunition to be used in his Hercules rifles and combination guns.
In 1910 the business was known as Mechanische Waffen und Munitionfabrik August Schüler. The name implies that the business produced or at the very least loaded their own ammunition. It appears that, as they existed in the same city (Suhl), Schüler got B.Stahl to produce cases for them. Later G.C. Dornheim (GECADO) produced the Schüler case types after it took over B.Stahl. G.C. Dornheim is the only company that produced all of the standard Schüler calibers. Schüler cartridges have also been manufactured by RWS, DWM and G.Roth
In 1912 August retired and his son Richard Schüler (1879-1965) was given his fathers shares in the company and took over managing the business. In 1913/14 Richard acquired his uncle Oscar’s shares and became the sole owner. In 1914 the business was known as Jagd und Schieben- Gewehrfabrik August Schüler,
Later name changes were:
1916- August Schüler, Werkstätten für modernen Gewehrbau,
1930- ASS-Waffenfabrik August Schüler (ASS = August Schüler, Suhl)
After WW1 in 1927 the largest Schüler case was introduced, the 500 Schüler (12.7x70). A 404 Schuler Magnum (10.75mm : W107) was also evidently designed by 1929. Barnes states that the 6.5x68 (W59) was “actually developed by Schüler at an earlier date from necked down 8x68S cases” but this appears incorrect and this cartridge was purely an RWS development. See:
404 (10.75x70) Schüler Magnum (W107)
11.2x60 Schüler (W17)
11.2x72 Schüler (W18)
11.2x72R Schüler (W19)
500 (12.7x70) Schüler (W20)
References: Schüler 1929 Catalog , c1932 catalog