There were always gangs in London," says Target, producer and unofficial spokesman for east London grime rappers Roll Deep as we sit with several of the 20-strong collective in their new Limehouse studio.

"That's the way it is when you come from where we come from. We were involved in it, but we grew out of it. Now, it's so easy to get a gun in London that some of these kids won't get the chance to grow out of it because they won't live long enough."

As London digests the details of the third teenage murder in two weeks - the Valentine's Day shooting of 15-year old Billy Cox in his bedroom in north Clapham - Roll Deep offer me an insider's insight into the street subculture that provides the dramatic backdrop for their music. On record, it can be a vibrant, exciting culture - but it's one that has a deadly underside.

"They'll never get all the guns off the streets," says the fresh-faced Danny Weed, one of two white members of the crew. "And even if they did, people would probably stick to killing each other with knives."

Lest this sounds like complacency, Roll Deep are keen to make known their collective belief that inner-city youths need to take responsibility for their actions, a position they reiterate on their track Badman, the video of which was used last November in a hardhitting TV campaign for Operation Trident, the Met campaign set up to combat gun crime in the black community.

However, they also raise valid points about the external factors that affect gun violence, including the media's reporting of events.

According to Target, TV and newspaper reports mentioning specific gangs and giving details of the "territory" they supposedly control only exacerbate the problem.

"These kids aren't shooting each other for money," he says. "They're doing it for respect and recognition; so they're all walking round now boasting, saying: 'We're on the telly now. That's how big and bad we are.' They're over the moon about it."

Another even more serious issue he raises relates to the supply of guns. "They call it black-on-black crime and it is, but who's making these guns? Who's bringing them into the country? Probably not a black man."

Roll Deep's music career started almost a decade ago when they were among the founders of Rinse FM, the influential pirate radio station broadcast from mobile studios in faceless council tower blocks that has proved a tough but effective training ground for young urban talent.

Under the auspices of rapper and producer Wiley, one of the scene's leading lights, they began backing up their radio appearances with live outings at garage raves.

Like many urban acts, they are a loose collective rather than a clearly defined group, their line-up on recordings and on stage rotating according to requirements.

By the time they parted company with Wiley and Mercury Prize-winning rapper Dizzee Rascal three years ago, they had been instrumental in the development of the unique London hybrid of rap, garage and drum'n'bass known as grime.

They have some things in common with the better known So Solid Crew, but where their promising career was cut short by crime, violence and disappointing music, Roll Deep have stayed out of trouble and concentrated on their tunes.

Things could easily have turned out differently. Raised on housing estates around Bow and Poplar, the group, who have been friends since childhood, have had first-hand experience of the gang culture that has spawned the recent murders in south London.

"We're all in our mid-twenties now, but when we were teenagers, there was always violence. We all wanted to be seen as tough.

"We used to have our little crews and have fights with kids from other estates," says rapper Flow Dan, a deep-voiced man with hair plaited into "corn rows", gold teeth in his mouth and an intense gaze.

"We know a lot of people who stayed on that path, got into selling drugs and all that. It could easily have happened to us. But music stopped us getting too deep into it.

"We had something else to concentrate on, something else to feel good about. We didn't have to prove ourselves as bad boys because we were proving ourselves as rappers and producers."

Having set the grime scene alight with tough club anthems such as When I'm 'Ere, Roll Deep went on to become the first grime act to make music in song format, rather than simply MC-ing over DJ sets.

Last year saw a national tour and high-profile support slots with 50 Cent and Snoop Dogg. Despite critical acclaim, their debut album, In at the Deep End, upset purists by introducing melodic samples and sung choruses into grime's gritty, minimal format of crisp drum machine beats and hard, crunchy bass lines.

The hostility it provoked was shortlived, however. "At first, you'd hear the odd person saying, 'Look at Roll Deep, they've sold out and done a cheesy pop song.'

"Now, call up any grime artist, listen to what they're working on. The stuff they're going to be releasing this year is going to be full of happy pop songs, choruses, samples.

"Other artists were scared to do something more melodic. Now they're all doing it. People are starting to make a lot more songs about parties, drinking and relationships."

Despite the album selling an impressive 75,000 copies and spawning the singles The Avenue and Shake a Leg, which charted at 11 and 24 respectively, Roll Deep were dropped from their label, Relentless, late last year.

Undeterred, they soon set up their own label, Roll Deep Recordings. Their new album, Rules and Regulations, out next month, signals a return to their roots, with an array of tough, synthetic beats and basslines backed up by quickfire lyrical flows.

Featuring guest vocal and production contributions from Wiley, it's a more mature and accomplished work than the last, showing greater lyrical and musical variety than before, from the ragga-tinged rant of Babylon Burner to the romantic R&B-flavoured study of relationships that is Floating Thru Da Sky.

However, though Roll Deep's last album was altogether more commercial, and perhaps more palatable to the mainstream, earlier lyrics have included macho posturing and violent imagery: "We've had a few gun lyrics in our music before," Target admits.

"A few people will always take music too literally, but that stuff has always been part of hip-hop and grime and most fans understand that it's poetic, a metaphor." He has a point.

Throughout the history of hip-hop, rappers have used the imagery of weaponry to describe their lyrical or sexual prowess.

Their group's bleak, vivid Badman, on the other hand, is a track in the longstanding rap tradition of storytelling.

"It was just another song about a situation that happens in people's lives - the lives of people we know."

The song's video has been downloaded on YouTube 160,000 times and stayed in Channel U's top three videos list for six weeks.

Making the song was one thing. Teaming up with the police, however, was a big step for a group whose core audience regards the force with, at best, a deep-seated mistrust.

"We heard the police wanted us to help them and we had to think hard about the repercussions. We knew some people might think less of us because of it. But we realised that this wasn't some PR thing promoting the police," chips in Flow Dan.

"It was promoting the idea of us not killing each other. We didn't do it because we love the police and agree with everything they do - we did it because we love our community."

What cemented their decision to work with Operation Trident was a fundamental change in their community. "Ten years ago, there would be one or maybe two guys on the estate who had a gun and everyone would know who they were.

"They'd be in their twenties, and they'd have it for a reason, like if they were moving a lot of drugs, they'd have it in case someone tried to rob them," says Flow Dan.

The most chilling development he has observed is the ease with which weapons can now be obtained: "When we were young, even if I was a real bad boy and wanted a gun I'd have had no idea how to get one.

"Now, if you told me you needed a gun, I could pick this phone up, make two or three calls, and have it ready for you tomorrow," he says, holding his mobile towards me ominously.

Roll Deep are clearly in some despair about what's happening to the community they grew out of; they offer no quick-fix solution to the current crisis.

But with their mature new album they at least offer a fine assertion of their determination to make their own way, to rise above it all. They are setting a powerful example.

If even a few of the teenagers who look up to them learn that they, too, can go against the grain and refuse to bow to peer pressure, Roll Deep will have made an important contribution to a desperate situation.

• Rules & Regulations is released on 26 March.