what is the average shot volume (cm 3) when the shot diameter (cm) is less than 6.04?
CREATE TABLE "english_gun_classes_c_1800_citation_need" (
  "gun_class_pdr" real,
  "shot_diameter_cm" real,
  "shot_volume_cm_3" real,
  "approx_service_bore_cm" real,
  "mass_of_projectile_kg" real
);
SELECT AVG("shot_volume_cm_3") FROM "english_gun_classes_c_1800_citation_need" WHERE "shot_diameter_cm"<6.04;