The demonstration by Security Labs came Friday as the country grappled anew with the hot-button issue of gun ownership in the aftermath of a deadly shooting rampage in a Colorado movie theatre.

"This country has reached a level of violence that America ought to do something about it," Marc Tobias of Security Labs said as he demonstrated his findings for AFP at the infamous Def Con hacker conference in Las Vegas.

"Do kids have a second amendment right to have weapons?" he asked rhetorically, referring to a part of the US Constitution assuring citizens the right to bear arms.

"It's not a gun control problem; it is a people control problem."

Tobias said that Security Labs turned its attention to gun safes after the three-year-old son of a now-former sheriff's department detective in Canada was shot to death by a sibling with a pistol that had been locked away at home.

Researchers toyed with the Stack-On safe at issue and discovered it could be opened by simply tipping it a bit and then dropping it, with the jar of the impact causing it to unlock.

Intrigued, the pair scrutinized another half-dozen or so models of gun safes from the Illinois-based company.

"They could be opened with wires, a drinking straw, bouncing...," Tobias said, rattling off unsophisticated techniques used to crack gun safes.

"They are putting everyone who buys these at risk."

A high-end gun safe with a fingerprint scan activated lock can be opened using a pair of paper clips thanks to a hole under the scan pad that allows access to the latching mechanism inside, Security Labs Toby Bluzmanis showed.

The demonstration at Def Con included video of a three-year-old child opening a gun safe by lifting it part way and letting go. Tobias also uploaded video of gun safe cracking to YouTube.

Bluzmanis told of his young son noticing him trying to crack gun safes and offered to help, then curiously tapping key pads and poking things in cracks or key holes.

He asked his son to move the 30-pound safe. The boy lifted it part way and pushed before dropping it, with the door unlocking, the father said.

"This is a game for them," he said of a typical reaction by children to the challenge of a locked gun safe. "At three years old they can't pick it up, but they grab it and try to move it around then drop it and, bingo, it opens."

The researchers focused most intensely on Stack-On safes, but also checked out models from GunVault, BullDog and AMSEC.

The safes tested are widely available at sporting goods shops as well as retail giant Wal-Mart and online shop Amazon.com, according to Security Labs.

"I've only found one gun lock in the country that I think is worth a damn, and it is made by a guy in California," Tobias said, identifying the maker as Omega Safety Systems.

Omega locks consist of expandable rods that slide into gun barrels and can only be removed with special keys, according to its website.

Sharing ways to crack gun safes with the thousands of hackers at Def Con was intended to call attention to the situation, according to the researchers.

"This is about insecurity engineering of real products that protect real people," Tobias said. "It isn't about how to open the gun safes; it is about how easily they can be opened."

The results of a Gallup poll released late last year indicated that there were guns in 47% of US homes or somewhere within easy reach on the property.