Marines were slow because they trained with a tried a true weapon and the commanders new a war was coming. Thats what Ive read before. But show a marine an advantage they will adapt. John Garand showed the army his rifle chambering a 277 caliber. The marines and Army told him it was the wrong caliber. He came back with a .30/3006. They army took it the marines true to their reputation were a little skeptical. They arent to stupid(contrary to idiots that dont know them) to figure things out. History is made and the boys are still MAGA.
The story goes that the Army looked at a store of several billion rounds of .30-06 ball and said no to the .276 Pedersen.