user: Question: Name the barrel length for barrel twist of 1:7
Columns: ['Colt model no.', 'Name', 'Stock', 'Fire control', 'Rear sight', 'Forward assist', 'Case deflector', 'Barrel length', 'Barrel profile', 'Barrel twist', 'Hand guards', 'Bayonet Lug', 'Muzzle device']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['AR6320', 'AR-15 Lightweight', '4th Generation', 'S-1', 'A1', 'Yes', 'Yes', '16 in.', 'A1', '1:9', 'Short Ribbed', 'Yes', 'A2']
SQL:

assistant: SELECT "Barrel length" FROM "Table" WHERE "Barrel twist" = '1:7';