Snatch questions, -- Probably spoilers

Watched the movie the other night, and thought it was a pretty good movie. Not as good as lock-stock, a too much was way too similar to lock-stock. What exactly is a replica gun. I was assuming that it was a non functioning gun, but the fact that it shoots blanks was confusing, since a gun that can shoot blanks can shoot bullets. Did Ritchie just replica guns up, are they just cap guns or what.
One of the other things I didn’t understand was the hustle Brick Top used. Mickey was a last minute replacement, completely unknown, and half the size of the other guy. Not exactly the first guy I’m gonna throw my money on without good odds. So why would they want him to take a dive? I guess any sure thing is good for business, but setting it up to go they way everybody expects it to go doesn’t seem worth the risk of getting caught and losing all your credibility. Unless round 4 was the key. Is there so much beting on the specific round that it makes it worth the whole thing? I seem to be woefully short on contacts in the British underground fighting industry. :slight_smile: