Here’s one distinctive sign of Stephen Curry’s mind-numbing free-throw proficiency: He becomes angry when the ball even grazes the rim in practice. His shot falls and he still grimaces, frustrated with himself.

That happened occasionally during Curry’s free-throw contests against Warriors head coach Steve Kerr during the 2014-15 season. They enlivened their friendly competition by awarding two points for a swish and one for all other makes.

Kerr estimated he converted more than 95 percent of his attempts throughout the season — and lost, almost always.

“Steph could basically swish on demand and I couldn’t,” Kerr said Thursday, “and that was the difference.”

Curry counts as one of the best free-throw shooters in NBA history, as the first five games this season vividly illustrated. He’s 47-for-47 entering Friday night’s game against Washington, a relentless parade of rhythmic, solitary, accurate 15-footers.

His overall streak of free throws made stands at 49, dating to last season. That puts Curry within striking distance of Rick Barry’s franchise record (60), but only about halfway to the NBA record held by Minnesota’s Micheal Williams (97).

Still, this run merely reinforces the wider-angle perspective on Curry. He has led the league in free-throw percentage three times, topped by his personal-best 93.4 in 2010-11, his second season as a pro.

Curry’s career percentage stands at 90.31, third all-time behind Steve Nash (90.43), now a Warriors consultant, and Mark Price (90.39). Nash holds no illusions about maintaining the top spot in the years ahead.

“My money is on Steph to leave the game as the best free-throw shooter of all time, or be that before he leaves,” Nash said.

Kevin Durant also is no slouch at the line, even if he’s struggling at the moment (68.2 percent this season). Durant led the NBA in free-throw percentage in 2012-13, and his career mark of 88.1 percent puts him third among active players behind Curry and J.J. Redick.

Even so, Durant willingly whipped a pass to Curry in the closing seconds Wednesday night, with the Warriors trying to protect a three-point lead. Durant is no fool, either: He wants Curry at the line when it matters most.

“He’s automatic, man,” Durant said. “We expect him to make every one of them. When he misses, it feels like the apocalypse is coming.”

Then it’s a good thing Curry hasn’t missed this season.

Curry’s routine while preparing to shoot a free throw is simple and efficient: deep breath, one low dribble (with his right hand), knee bend, smooth-as-silk release. Rinse and repeat.

His deep breath was more exaggerated than usual Wednesday night, for good reason. Curry absolutely is aware of his streak and clearly wants to keep it going.

“I am a little more conscious of that (deep breath), trying to make sure I stay in the moment,” he said later. “You’ve seen it more the last two games because of the situation, to be honest.”

Or, as Nash said of climbing into “the zone” during a streak like Curry’s: “It feels easy, simple and seamless. Then it becomes about the streak, and it’s not simple and seamless.”

This probably represents Curry’s biggest obstacle in extending his run into the 50s and 60s. Let’s face it: The physical challenge of making free throws is modest for a shooter like Curry. It’s akin to a tap-in putt in golf.

But there’s more at work in an NBA game racing along at high speed.

Then, suddenly, a foul occurs, the action stops and the shooter must abruptly slow down and tackle an altogether fresh task.

“Free throws are different shots, because there’s an emotional component — in the heat of battle, to push everything aside and be in a little bubble for a moment,” Nash said. “For a guy like Steph, the shot is a gimme.

“The only reason he misses one is because he’s not super in the moment or clear-headed, if he’s thinking about 20 things — as he should be as point guard of the Warriors.”

One thing at the forefront of Curry’s mind these days is reaching the free-throw line in the first place. He’s historically not a high-volume foul shooter, given his preference to remain a high-volume three-point shooter.

Curry also is smart enough to see defenses pushing him away from the three-point line. His drives to the basket have increased the past few seasons, leading to more fouls — he had a career-high 5.1 free-throw attempts per game two years ago, then 4.6 last season.

This season, he’s averaging 9.4 free-throw attempts. It’s obviously a small sample size, but 9.4 is still an eye-catching number. Those are free points, as Durant likes to say.

Assistant coach Bruce Fraser has encouraged Curry to work at “selling fouls.” That’s one big reason Houston guard James Harden averaged more than 10 free-throw attempts per game in each of the past three seasons, as he sought contact and convinced referees to call a foul.

Curry, no natural actor, is gradually learning the fine art of shouting when he takes a shot in traffic, or demonstratively reacting at the slightest nudge or bump.

“I’m not great at it,” he said. “My tendency, especially when I’m in space, is to just play basketball. And basketball to me is trying to score, not really looking to create contact and get the foul called.…

Fraser “has been really consistent with his message, because he thinks there are times I can kind of let the ref know what’s going on. But it’s hard for me to always be in that mind-set, because I’m trying to create space, get my shot off and play basketball the way I’ve played it my entire life.”

Curry usually lines up his right toe with the nail at the exact center of the free-throw line on most basketball courts. Kerr, an 86.4 percent foul shooter during his career, preferred to straddle the nail.

Durant has his own style, turning his body and facing slightly to the left. He still watches Curry closely, as a reminder of good tempo.

“It’s just his rhythm,” Durant said. “Steph does one quick bounce and one hop, gets into his motion and then it’s just a flick of the wrist.”

Dribble, flick, swish. So easy, right?

Ron Kroichick is a San Francisco Chronicle staff writer. Email: rkroichick@sfchronicle.com Twitter: @ronkroichick

Record books

Career free-throw %

(active leaders)

Player FT% Stephen Curry 90.31 J.J. Redick 88.85 Kevin Durant 88.11 Dirk Nowitzki 87.90 Damian Lillard 87.63

Season free-throw %

Player* Season FT% Jose Calderon 2008-09 98.05 Calvin Murphy 1980-81 95.81 M. Abdul-Rauf 1993-94 95.63 Ray Allen 2008-09 95.18 Jeff Hornacek 1999-00 95.00

Note: Among official qualifiers

Consecutive

made free throws

Player Team No. Micheal Williams Min. 97 Jose Calderon Tor. 87 Dirk Nowitzki Dal. 82

Topping the charts

A look at the NBA’s all-time leaders in free-throw shooting percentage: