You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "What rifle is the basis for the the magazine-fed, gas-operated semi-automatic rifle designed to be manufactured with the extensive use of aluminum alloys and synthetic materials?" whose answer is United States military M16 rifle.
Each document should contain about 30 words, and these documents should contain useful information.

Query: HBAR rifle design details
Useful Output:

Doc 1: The "HBAR" in the name refers to the Heavy Barrel, a key component contributing to the rifle's exceptional accuracy. The heavier barrel helps
Doc 2: The design featured lightweight materials and innovative features, including the use of gas impingement for operation. The rifle was initially
Doc 3: DETAILS. Credit: Gary Chalker. Creative #:. 1193122574  Hand Gun close up at Carnival Fair style Shooting range in Pattaya Thailand.
Doc 4:  HBAR variants of AR-15-style rifles are legal in MD. Curious about this, I researched Assault Weapons regulations in all the applicable
Doc 5: These rifles, classified as “Rifle, Cal.30 T48 FN” by the Army, were 21-inch four-groove, right-hand twist barrels that taped out to 47.25-