What is the  p1 diameter (mm) when .300 lapua magnum is the chambering?
CREATE TABLE "bolt_thrust_estimations_for_various_rifl" (
  "chambering" text,
  "p1_diameter_mm" text,
  "a_external_cm_2" text,
  "p_max_bar" real,
  "f_bolt_kgf" real,
  "f_bolt" text
);
SELECT "p1_diameter_mm" FROM "bolt_thrust_estimations_for_various_rifl" WHERE "chambering"='.300 Lapua Magnum';