What are all the 100 m group (mm) with a .308 winchester cartridge type of .300 winchester magnum cartridge type
CREATE TABLE "design_details" (
  "308_winchester_cartridge_type" text,
  "100_m_group_mm" text,
  "100_m_group_moa" text,
  "300_m_group_mm" text,
  "300_m_group_moa" text
);
SELECT "100_m_group_mm" FROM "design_details" WHERE "308_winchester_cartridge_type"='.300 Winchester Magnum cartridge type';