With what type of chambering is the F bolt n (lbf) and the P max (bar) 3900?
CREATE TABLE "bolt_thrust_estimations_for_various_pist" (
  "chambering" text,
  "p1_diameter_mm" text,
  "a_external_cm_2" text,
  "p_max_bar" real,
  "f_bolt_kgf" real,
  "f_bolt" text
);
SELECT "chambering" FROM "bolt_thrust_estimations_for_various_pist" WHERE "f_bolt"='N (lbf)' AND "p_max_bar"=3900;