Free Fire feels like the result of a clear vision, expert planning and a lot of patience. It's quite reminiscent of Tarantino's Reservoir Dogs and a lot like a stage play. To keep track of where all the various characters are, who can see who, who's been shot, how much blood they've lost etc is pretty incredible. The writing was on form and had the entire cinema in stitches, something I love about group viewing. It really becomes a shared experience when you can hear others having the same level of involvement as you.
It's a much more conventional film than Wheatley's previous work so it's difficult to compare with his back catalogue. But if you're comparing it to other shooter films, it easily surpasses. It proves that a film doesn't need to be overly complex or long to be clever. It just needs to be firing on all cylinders. Pun intended.