AR-15 assault rifle

Joseph Pereira, 15, shoots an AR-15, the country’s best-selling style of long gun, for the first time at Markham Park shooting range in Sunrise, Fla., Dec. 12, 2015.

Let's talk about the differences between an AR-15 (the type of gun used in the Parkland, Fla., school shooting) and the military versions M4 and M16.

Unless you're a gun aficionado, law enforcement officer or military veteran, you may not know the details. C.J. Chivers, a military veteran and war correspondent for The New York Times, is here to help. His book, "The Gun," is considered the go-to read on the Soviet creation of the AK-47 and the assault weapons that have come after it.

He writes:

"The National Rifle Association and other pro-gun groups highlight the fully automatic feature in military M4s and M16s. But the American military, after a long experience with fully automatic M16s reaching back to Vietnam, decided by the 1980s to issue M16s, and later M4s, to most conventional troops without the fully automatic function, and to train them to fire in a more controlled fashion.

"What all of this means is that the Parkland gunman, in practical terms, had the same rifle firepower as an American grunt using a standard infantry rifle in the standard way."

This report from Chivers and others at The Times is a must-read given today's talk of congressional bans of assault-style weapons, particularly the AR-15. In words and video, it illustrates the differences and similarities, not to mention that civilian versions of these weapons allow untrained shooters to cause mass-casualty events.

Chivers writes:

"A New York Times analysis of a video from a Florida classroom estimates that during his crime the gunman fired his AR-15 as quickly as one-and-a-half rounds per second. The military trains soldiers to fire at a sustained rate of 12 to 15 rounds per minute, or a round every four or five seconds."

-- Phillip Tutor