The What Richard Did star has gone from being an unknown jobbing actor to a potential superstar in just a matter of months.
And it is all down to the 20-year-old's performance in Lenny Abrahamson's controversial flick.
The Irish-made movie charts the downfall a Dublin teenager whose world comes crumbling down around him.
The movie is loosely based on Kevin Power's Bad Day In Blackrock, which is itself loosely based on the assault on and killing of Brian Murphy outside the Burlington Hotel in August 2000.
Reynor's performance has wowed audiences both home and abroad and the Herald recently revealed how the movie has been sold to Australia, France, Scandinavia and the UK.
Following this success, Jack has signed up with one of the world's biggest talent agencies, and has managed to bag a role in upcoming US comedy The Delivery Man.
Reynor will share the screen with Wedding Crashers star Vince Vaughan (42) and Irish funnyman Simon Delaney.
Delaney has been carving out his own career Stateside, having completed stints in Julianna Margulies' series The Good Wife and Kiefer Sutherland's Touch.
A source close to Reynor said it was a "pure coincidence" that the two Irish actors had ended up in the same film, but Reynor was "delighted" to be working alongside Delaney.
The feature is being produced by film legend Steven Spielberg.
It has been reported that Spielberg was so impressed with Reynor's audition tape he hired the young actor straight away.
Reynor flew out to New York last month to begin filming.
He returned home briefly for a break and is set to resume filming next week.
This will be Reynor's first US role, and could be his big breakthrough into the American market.