SAN FRANCISCO (CBS 5) — California has some of the strictest gun control laws in the nation. But one wouldn’t know that going to the firing range these days. AR-15s and AK-47s are the must-have guns of choice. How can that be?

Every time California tightens up the assault weapons ban, the gun industry finds a way around it. The latest example involves a tiny device.

John Largaespada loves his AR-15 and goes to the range every week to fire it. And he’s got plenty of company. “There is usually like a 30 minute to an hour wait for rifle lanes,” he said.

That’s because the most popular guns at the range these days are semi-automatic rifles. In a state with some of the strictest gun laws in the nation, how is it these military-style guns are legal?

Brian Normandy is an instructor at Jackson Arms. “As long as we don’t have a detachable magazine in it, it’s actually a legal firearm,” Normandy said.

Other states allow people to use their finger to pop out the magazine and quickly reload. It’s called a detachable magazine, and in California, its use in combination with other features such as a telescoping stock or pistol grip is illegal.

The intent is to slow down the process of reloading the weapon. But many target shooters don’t like the reloading hassle. “For me to use this on the range, I would have to open up the receiver and top load it,” said Normandy.

To get around this, gun manufacturers are selling firearms to Californians with what is called a “bullet button.”

The user uses the tip of a bullet to release the empty magazine and pop in a new one. The button doesn’t work with one’s finger, so the magazine is considered “fixed.”

That makes it an assault rifle that everyone is calling “California legal.”

“Of course manufacturers don’t want to break the law, so they are going to make a legal version of it that doesn’t meet the restrictions,” said Normandy.

And it’s a hot seller. CBS 5 went undercover to a recent gun show at the Cow Palace in Daly City and found “California legal” assault rifles throughout. There were also were gadgets to release the bullet button, in case one doesn’t have a spare bullet around, such as the “Mag Magnet.”

So why isn’t law enforcement cracking down on what appears to be a loophole in the state’s gun control laws? CBS 5 put the question to Bay Area police departments. None would comment, same with the California Department of Justice.

Even Senator Dianne Feinstein, one of the strongest gun control advocates in the country, told CBS 5 she was “not able to participate.”

But at least one group in Washington D.C. is watching the issue closely. “If the bullet button assault weapon is allowed to come into the state then the California assault weapons ban basically doesn’t exist any more,” said Josh Sugarmann with the Violence Policy Center.

Sugarmann said the bullet button marketing campaign is huge. “We are talking about every major assault weapons manufacturer in America. Companies like Bushmaster, Colt, Smith and Wesson and myriad others. And the reason they are all focusing on bullet buttons is because California’s ban has been so effective, right now they view California as the last great market,” he said. “The end result is that California law enforcement, California citizens will all be placed in jeopardy because of this marketing move by the firearms industry.”

But gun rights proponents like Brian Normandy point to a lack of hard data showing assault rifles being used in crimes. He argues, why should law-abiding citizens be deprived?

“If Californians are wanting these things, someone’s going to step up and make money while doing it and why not? I mean that’s exactly what free America is,” said Normandy.

Out on the rifle lanes, Largaespada said he can see both sides. “The bullet button, I could see where I guess officers and stuff would be concerned about that,” he said. But for him, it’s all about the thrill of owning an assault rifle.

“It’s an adrenaline rush. You just feel like you’re on top of the world,” he said.

(Copyright 2012 by CBS San Francisco. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)