/u/OxygenIsOverrated5

No - see my post here - TLDR diminutive forms of the katana were used as a "main weapon", however soon taken over by other weapons. They again became the "main weapon" during the period of peace throughout the Edo, but this hardly counts (in my opinion anyway). Also, at what period are you referring to when you say the samurai stopped being horse archers? You could argue that, after the introduction of the matchlock and subsequent development, this was abandoned, however I feel like this isn't what you mean - feel free to clarify though.