user: Question: How many case deflectors are there for the Colt 646? 
Columns: ['Colt model no.', 'Military designation', 'Barrel Length', 'Barrel', 'Handguard type', 'Buttstock type', 'Pistol grip type', 'Lower receiver type', 'Upper receiver type', 'Rear sight type', 'Front sight type', 'Muzzle device', 'Forward assist?', 'Case deflector?', 'Bayonet lug?', 'Trigger pack']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['601', 'AR-15', '20 in (508mm)', 'A1 profile (1:14 twist)', 'Green or brown full-length triangular', 'Green or brown fixed A1', 'A1', 'A1', 'A1', 'A1', 'A1', 'Duckbill flash suppressor', 'No', 'No', 'Yes', 'Safe-Semi-Auto']
SQL:

assistant: SELECT COUNT("Case deflector?") FROM "Table" WHERE "Colt model no." = '646';