Here a way to milk out a few more:
let all the zombies come in. Get a group of three to form a straight line. Shoot through all three, aiming at the leg. 6 shots before a knife is usually safe. Experiment with how many shots to give the 2nd and 3rd zombies so you can still knife them. You get triple points this way(if you hit all three), and can save ammo and still get the same or more points.
also, FYI: full pistol clip plus one knife on round 2 for max points (or one chest shot Kar98k plus knife). Two leg shots with thompson plus knife on round 3. A couple of close range headshots from pistol plus one knife on these rounds too. Now you can get jugger and speed by round 4