Why does it take two shots to kill someone with the Gewehr in CoD:WaW HC mode?

The Gewehr does 40-30 damage (depending on range), and mode health is 30 without Juggernaut. So why does it almost always take two shots to kill someone at mid-long range when the Gewehr does a MINIMUM of 30 damage (unless the bullet had to an object)? Surely most people aren't using Juggernaut?