How many case deflectors are there for the Colt 646? 
CREATE TABLE "summary" (
  "colt_model_no" text,
  "military_designation" text,
  "barrel_length" text,
  "barrel" text,
  "handguard_type" text,
  "buttstock_type" text,
  "pistol_grip_type" text,
  "lower_receiver_type" text,
  "upper_receiver_type" text,
  "rear_sight_type" text,
  "front_sight_type" text,
  "muzzle_device" text,
  "forward_assist" text,
  "case_deflector" text,
  "bayonet_lug" text,
  "trigger_pack" text
);
SELECT COUNT("case_deflector") FROM "summary" WHERE "colt_model_no"='646';