High-capacity magazines are the deadliest of gun cartridges. They come in cases of 30, 40, 60 and even 120 rounds.
These magazines are maximum, economy-sized firepower packed into a steel cartridge. When strapped into a pistol or semi-automatic rifle, a shooter can fire non-stop until the magazine is empty. By then, the damage can be devastating.
That is why the Baltimore County Police Chief Jim Johnson wants to outlaw all but the smallest of these magazines. Johnson, the Chair of the National Law Enforcement Partnership to Prevent Gun Violence, wants to limit them to a capacity of 10 rounds.
The fewer the bullets, the more often the shooter has to stop firing, eject the empty cartridge and load another one.
A lot can happen in the window of time it takes to reload, Johnson said.
"Folks that are being attacked have time to react, to close that distance in," he said. "I think any football player in America would like to have four-and-a-half seconds to get to the quarterback without any of the offensive players."
An expert shooter like a police officer can switch magazines in less than two seconds. But for a nervous, scared adolescent, it would take much longer, Johnson said, which can be crucial.
During the Tucson, Ariz., attack on Rep. Gabby Giffords, gunman Jared Loughner was wrestled down when he stopped shooting to reload his 9-millimeter pistol.
During the Aurora, Colo., movie theater shooting spree last July, police say James Holmes' assault came to an end when his semi-automatic rifle jammed.
"As we've seen in America today, there have been several attacks where that reload is vital," Johnson said. "Tragically, in the shooting of a congresswoman, the reload was instrumental.
"We've also seen this in Baltimore County, in a school shooting that we had, where the reload became very instrumental in allowing the teacher to actually tackle a student that was trying to reload a double-barreled shotgun," he said.
Last week at Sandy Hook Elementary School in Newtown, Conn., police believe Adam Lanza was armed with high-capacity magazines. He fired at least 30 times before having to stop to reload.
Johnson said there is no reason that the general public should have access to high-capacity magazines.
"I have to advise you that even for law enforcement, 100-round magazines, 50-round magazines, have no place for law enforcement," Johnson said. "Certainly, we believe that limiting a magazine to 10 rounds, what was in place from '94 to 2004, is wise and certainly could save lives in America."