I preface by saying I thought this was a good film, well acted and enjoyable (although not in the fun lovin' sense). I did, however, find it problematic. It seems to me two things have to be present truly to be gripped by the centre of the film: (i) belief in what was going on, or at least the willing suspension of disbelief, and (ii) investment in (at least one of) the characters.
Unfortunately, I felt the film failed in both regards. The central part of the film was certainly well directed and well acted and consequently tense. However, a couple of little things pulled me out of the 'reality' of it, which have to be put down to insufficient work on the concept and script. The betting made no sense. It seemed clear to me the filmmakers were aware of this and kind of tried to gloss over it, but they also tried to add tension via the minor players, suggesting extra pressure from the losing bosses negotiating to bet on those contestants left in. As I say, it made no sense.
There were a few other small things, but the other glaring one it seemed to me was the history of the other finalist. I can't remember the precise numbers but it was suggested he had won such events several times before and triumphed in the final duel several times. This was utterly implausible, as it remained fundamentally a game of chance, certainly in the early rounds. Were there rounds of 1, 2, 3 and 4 bullets before the duel? So 5/6 x 4/6 x 3/6 x 2/6 chance of survival? Less than 1 in 10? Repeated over many competitions? And why would betters be obssess over the calibre of the competitor when it was fundamentally a game of chance? I'm guessing people will disagree, but as I say this all pulled me out of the moment.
It also, of course, suffered the inevitable fate on the level of peril that these films can sustain, in that we know our protagonist is going to survive deep into the competition.
As for my second point, I should say I really enjoyed the opening part of the film, perhaps more than the competition part. However, the characterisation of the protagonist was limited and what there was didn't make me care about him. Pulling both points together, it seemed to me he had insufficient motivation to be heading off into the unknown as he did.
It's a long time since I watched it all the way through, but The Deer Hunter is the obvious comparison to this film. It seems to me that succeeded where this film failed. It spend upwards of an hour with the characters, allowing you get to know them, flaws and all, and the setup was more believable / capable of allowing suspension of disbelief.
Anyway, excellent choice and much enjoyed.