Buk and S300/S400 are different things. Buk is self propelled all-in-one system, which has four rockets and integrated radar [1]. Buk's rockets range is about 5

Buk and S300/S400 are different things. Buk is self propelled all-in-one system, which has four rockets and integrated radar [1]. Buk's rockets range is about 50km. While S300/S400 have mich bigger rockets thus range, 300 and 400km respectively [2]. 1. https://en.m.wikipedia.org/wiki/Buk_missile_system https://en.m.wikipedia.org/wiki/Buk_missile_system 2. https://en.m.wikipedia.org/wiki/S-400_missile_system https://en.m.wikipedia.org/wiki/S-400_missile_system