Sorry, RIB. You didn't get it. A schmidt Rubin is not a k31. Read below or my post above.
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Nope. Neither is correct. The k31 means Karabiner 31 (Year of issue)
The Karabiner Modell 1931 was a fully new design by Waffenfabrik Bern under Colonel Furrer and the first 200 troop trial rifles were made May 1931
Rudolf Schmidt (1832-1898 ) had long since died by the time the K31 was introduced and Eduard Rubin (1846 - 1920) was the one that was responsible for ammunition designs like the GP11.
Typical rifle designs by Schmidt were the 1889 rifle and the 1889/96 with the newer 1896 action that we also find in the later 1911 series .