You have a point, 25 to 50 kills in 5 minutes without dying? Brainstorming is fun. Not impossible... not probable... I doubt very many would be able to get that, unless the other team was afk or cheating to help you get it..., or if it was a FFA and you was in the zone, maximum luck, and various other superstitions here.
Not sure what would be a possible but difficult number to get. My personal best killstreak is 16 so that one is possible, but most difficult.