In minecratf I'll assume the amount of creepers you could dispose would be proportional with this variables, amount of rounds at hand, aim, caliber of the bullet, quality of the creepers armor, time you have from the moment you make the first shot to the moment they spot you and shot back at you... Too many variables... Let's just say this, a well trained, well armed, brave patriot could send to hell dozens of creepers as long as he is focused on the fact that what he's fighting for is worthy of fight for.