The Italian Carcano rifle starting with the Series 1891 were monolithic bolts (locking lugs integral with the bolt body head) like the early 1890s Mausers. I have owned a Carcano 91/41 rifle and currently own a 91/38 short rifle. The bolt head is not separate like the Lee-Enfield or Mosin rifles.
American references call it "Mannlicher–Carcano" or "Mauser–Parravicino"; the en-bloc magazine system resembles Ritter von Mannlicher's designs, and Carcano and Parravicino were involved in development, In Italy it is known as Modello 1891, M91, or "il novantuno" ("the ninety-one").
Those early Vetterli rifles were sometimes rebarreled to 6.5 Carcano valiber in the early 20th century.