Lead Gun Ian Shelton is setting a marker down, but he has every right to be bullish. From hardcore upstarts to alt-rock champions, his Californian charges are on the cusp of a major breakout on the back of sophomore effort 'God Save the Gun'. Their trajectory has been one of constant progression and evolution. To that end, if Militarie Gun keep on the same path, their future is assured.

Yet evolution is a bold move for a band rooted in hardcore – a genre often resistant to change. While Turnstile have been championed for challenging the expectations of hardcore in one direction, so too should Militarie Gun for their alt-rock leanings. Their sound draws just as much from the creativity of Modest Mouse or the pop-rock sensibility of Fountains of Wayne as it does from the hardcore mainstays like Sick of It All or Black Flag.

There have been trailblazers before, and Shelton finds himself in good company. The band is in London for promo interviews and two shows in East London dive bars. This afternoon, in a trendy rooftop restaurant, Shelton is joined by bassist Waylon Trim and producer Riley MacIntyre (LCD Soundsystem, Arlo Parks, Rina Sawayama). For the next two nights, they'll be the hottest ticket in town – and all this just days after playing a Californian show with hardcore icons Gorilla Biscuits.

This connection feels fitting. After all, Gorilla Biscuits feature hardcore legend Walter Schreifels (Youth of Today, Quicksand, Rival Schools, Walking Music, and countless more). If anyone understands how to upend the status quo in hardcore, it's Schreifels.

From the outset of 'God Save the Gun', Militarie Gun (completed by guitarists William Acuna and Kevin Kiley and drummer David Stalsworth) have no interest in retreading old ground. The pre-released singles' B A D I D E A' and 'Throw Me Away' are miles apart sonically and thematically – one a rabble-rousing pit anthem, the other a soaring slice of alt-rock. Even better, 2024's stop-gap single 'Thought You Were Waving' (which fits perfectly on 'God Save The Gun') is an anthem about reaching out for help and misinterpreting the signs.

"If we've written the song before, I'm not going to write it again," says Shelton. "Maybe, if enough time has passed and I feel there's more to explore in that territory, I'd explore it again. Or there'll be a song that is a sequel – like 'B A D I D E A' felt like a response to 'Disposable Plastic Trash', or like 'Do It Faster' and 'Disposable Plastic Trash' put together. And that was intentional – like anchoring the new record with a song that's so aggressive, when the record doesn't really have that aggression."

Shelton calls this an emotion-forward record from an emotion-forward band – and this is where Riley MacIntyre steps in. Producers are often tasked with drawing out a band's best, but journalists rarely hear about this from a creative or collaborative angle – and certainly not in the round with producer and artist in the same room at the same time.

The stories of Ross Robinson's involvement with At the Drive-In or Touche Amore are legendary – pushing the bands to emotional highs – and while MacIntyre's methods may not have been as oppositional as those displayed by Robinson, the result is equally as powerful.

It means we're treated to an opportunity to discuss process and ambition – and just how you tease what's inside someone's head out and make it have that emotional heft the band wanted.

One such song is standout 'Wake Up and Smile'. Brought to the studio by Waylon, it was initially dominated by electric guitar and synths, meaning it was a big rock song, far from the delicate alt-pop of the final version. Trim says the more he listened, the more the changes made sense – even if it was difficult to let go of the original vision. For MacIntyre, it's proof that the system works:

It's certainly time well spent. Shelton will comment that full-length debut 'Life Under the Gun' was recorded in just two days, and when you listen to both records back-to-back, they're a world away in tone, scope, and sound.

'God Save The Gun' was written over three years – a long time in today's world. It captures a significant chunk of Militarie Gun's ascent. Though it was a whirlwind, not every moment was sunshine – especially for Shelton.

Instead, while surviving on a lack of sleep and excess drink, Shelton came to a realisation that he needed help. 'God Save the Gun' is a record about addiction and the realisation of this addiction – but not the recovery, as he's at pains to point out.

"It's not about recovery at all. The recovery part doesn't come into play until we started recording the album, when I realised that I wasn't listening to what I was saying. I felt like, without me having to make a change in my life, I would be putting out something that was ironic or untrue.

The beauty of writing over such a long period means that the songs that made the cut are both meaningful and have stood up to repeated scrutiny. They also represent a marker – a stake in the ground, as it were – of Shelton's life at a particular point.

The other thing that gives these songs stakes is that they feel 'real'. Shelton talks about writing about himself as a caricature and trying to mask the real him from the world, but in facing up to this addiction, it makes for a powerful polemic about addiction.

"If I can listen to the song for three years before releasing it and still love it, I'm comfortable putting it out. When I began writing the record, I had just started drinking or maybe hadn't at all. The turning point was realising I was writing as a version of myself, not the real me. I felt shy playing a song like 'Daydream' with the lyric 'I've been drunk every day for a month', because I didn't want that to be true. Over time, I saw that it was me, and I was trying to hide it.

Further tied to this is the notion of world-building within a song. Joyce Manor are the masters of this, where every two-minute pop-punk blast is an entire story wrapped up in a perfect package. Militarie Gun are fast gaining on their Californian counterparts, and 'God Save The Gun' might be the best album in this regard – certainly from the punk rock world – since Joyce Manor's 'Never Hungover Again'.

"I'm quite comfortable with that as an idea," continues MacIntyre. "In fact, I keep art books in my studio for this very purpose. I often talk about films, but Ian can talk about them from the perspective of filmmaking. One of the first chats we ever had was about 'If this album was a movie, what movie would it be?' and I think that's really helpful as a way to almost triangulate the emotion.

"Like, someone can say 'I want it to be grittier' – but what does that mean? Like, does this Mark Rothko painting look gritty to you? I could describe certain Radiohead songs as gritty, but some people would describe them differently. So, what are we talking about here? Gritty could mean about the performance. It could mean that the vocals are slightly too loud, or it could mean distortion.

"So, Ian might say, 'It's more like a bedroom' or 'It starts in a bedroom'. So, that makes me think, 'Ok, it's small'. I tend to think of the full audio spectrum as the edges of the canvas. A lot of really expressive art doesn't quite reach the edge of the canvas. So, on that, I'll constrain the frequency spectrum. But then you go 'Well, is it literally a bedroom? Or are we thinking about what bedroom artists do?' And then where do you go with it – does it start in a bedroom and it's small and intimate, but does it then go widescreen, and how far does that go? We had all those sorts of conversations."

It's an interesting misnomer, but some bands often talk about capturing lightning in a bottle when they make their breakout, but there's just as much perspiration as inspiration going on behind the scenes to capture said lightning.

'God Save the Gun' might just be the purest example of this, with plenty of daughters killed along the way to present the 14 best songs possible for the record. Some big names got culled – for every Isaac Brock (Modest Mouse) and MS Paint there's a Mannequin Pussy lying on the cutting room floor – but if the songs didn't match the band's ambition, there was no room for sentiment.

It may be a stretch to call Shelton – and by extension Militarie Gun and Riley MacIntyre – visionaries, but there's no question that a vision underpins 'God Save the Gun'. It's urgent and compelling, willed into existence and moulded to the desires of its protagonists. It simply had to exist.

"I love listening to it," considers Shelton, as we discuss the purgatorial wait for people to hear the record. "For me, I make music that I want to listen to, and there's a gap there where no one's doing exactly what I want to hear. I have to step in and do it. It's the same reason as to why I started playing drums – well, there's no drummer, so I have to do it. It's the same reason I started Regional Justice Center. I love everything from the Jesus Lizard to Third Eye Blind. No one's doing that, so you gotta try it out.

If it is the final Militarie Gun record, at least they left us with an all-timer. 'God Save the Gun' indeed.

Militarie Gun's album 'God Save The Gun' is out now.