He never put bullets in the gun, but imagine the consequences if the barrel had twitched the curtain and the boy pointing the gun had been spotted.
"Mmm," says Winton, on the phone from Brisbane where he's in the middle of a book launch tour.
"If I'd lived in a place that was a bit more armed, like America, I would probably have been shot ... it took me a long time to think about what the hell I was doing. I was a safe kid; there was no violence, nothing to be afraid of."
But he was afraid. The family had just moved to Albany, south of Perth, and young Tim Winton was facing the challenges of a new school and no friends, underscored by the churn of puberty. The rifle, to him, "was a stilling point, a centring locus, like a religious icon", he writes.
"I felt like I was an alien in that I was unwelcome and unknown and I was never going to solve this problem," he explains. "I was anxious and somehow getting the rifle out and getting a bead on the people - I'd look through the sight and I could make the world smaller. I felt what was in the sight was contained and I felt I could control it.
"I was just boiling with these confused emotions and I couldn't find a way of expressing them. That's a thing we forget, that people don't always have words at their disposal. It doesn't mean they're not full of emotions."
After a few months, his obsession to play killer melted away; as an adult, he grew to abhor guns. But, he points out, he was lucky: he made friends and, always a big reader, he rediscovered words and "learnt to project myself with jokes and stories".
However, he writes, "For another boy, a kid in tougher circumstances than mine, the outcome might not have been so happy. The gun's slinky power has a special appeal to the young, the weak, the confused and the powerless.
"In your country and in mine, all over the world, we get sold this idea in entertainment that the guy with the gun is the guy that wins the argument and the gun is what gets the job done," Winton says.
"And then we're surprised that we are facing these disturbed young men going off and throwing their lives away on an armed jihad. They are almost always confused young men with no power, no future and as soon as they make that choice their future is sealed."
To him, the inability to express oneself is a hugely worrying issue.
"I guess I value language, not just because I'm a writer, but because it releases us from this sort of attitude to rage and servitude to suspicion."
Winton, 56, who is based on the coast north of Perth, says he sees men "all around us ... boiling with rage and confusion. They are men who never get past emotional infancy. The people around them have such low expectations of their progress or they are under pressure to not develop past this spoilt stage of infancy.
"So they don't find any means of expression other than with their fists or the buried aggression of capitalism where they yearn to be richer and more powerful than everybody else. It's all about that big swinging dick thing. You see it in politics, business, sport - it's all barely repressed violence."
That does sound like a textbook description of a current candidate for the US presidency.
"It's so obvious and so vivid and so livid," he snorts. "It even comes with its own colour. It's orange! And it's right on the surface, it's rage and misogyny and he is essentially an infant. He stands there stamping his feet, he's filled his onesie. But both there and here, the inarticulate, raging insider pretending to be an outsider, it prospers for some reason."
The elegantly written essays in The Boy Behind the Curtain cover a broad range of subjects, including the life-shaping experience of being the child of Church of Christ converts, the meditative enchantment of surfing, his fear of hospitals, his father's near-fatal motorbike crash, a plea to stop the killing of sharks and the inhumanity of successive Australian governments' treatment of refugees.
Winton also reveals that, as a young post-sniper teen, he had an unusual non-verbal way of wooing a girl: "My method involved a lot of stone-throwing. It was quite successful; we wound up married.
"Oh yes, excellent courting technique," he laughs. "I can recommend it. In my view, aim low. If you hit them on the head you're not likely to produce love, but feet and ankles ... talk about repressed violence!
"It was just enough to get attention but not enough to cause an ambulance to arrive."
The Boy Behind the Curtain
by Tim Winton
(Hamish Hamilton, $45)
