Question: when did the us military started using the m16
[{'answer': '1964', 'provenance': [{'wikipedia_id': '19901', 'title': 'M16 rifle', 'start_paragraph_id': 2, 'start_character': 3, 'end_paragraph_id': 2, 'end_character': 7, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '19901', 'title': 'M16 rifle', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 317, 'bleu_score': 0.8961853358642051, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8708416295869006024}, 'section': 'Section::::Abstract.'}]}]