I'm gonna take a wild guess and say this bot is full of shit, the mag looks like your typical 33rd glock mag, and it doesn't sound like it went through the entire thing. I can't guess a rate of fire, while it was extremely quick we need more samples to guess better. I don't think this went through more than 1/4 of the mag though.
edit: the flash out of the dust cover looks like you may have had an OOB.




