What is the muzzle device with a 1:7 barrel twist and a stock 4th generation?
CREATE TABLE "mt_and_cr_series_models" (
  "colt_model_no" text,
  "name" text,
  "stock" text,
  "fire_control" text,
  "rear_sight" text,
  "forward_assist" text,
  "case_deflector" text,
  "barrel_length" text,
  "barrel_profile" text,
  "barrel_twist" text,
  "hand_guards" text,
  "bayonet_lug" text,
  "muzzle_device" text
);
SELECT "muzzle_device" FROM "mt_and_cr_series_models" WHERE "barrel_twist"='1:7' AND "stock"='4th generation';