What are all the 300 m group (mm) with a .308 winchester cartridge type of ruag swiss p target 168 gr hp-bt
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 "300_m_group_mm" FROM "design_details" WHERE "308_winchester_cartridge_type"='RUAG Swiss P Target 168 gr HP-BT';