There is no way to start off with the Claw in any of the game modes, so the best way to begin getting kills is to start a Horde mode on beginner difficulty and wait for the weapon to drop of an enemy.

Choosing Marcus is a good strategy for Horde mode Claw kills because he is able to passively regenerate ammo for it in-between waves and firefights.

A solo custom Horde mode, without bots, on wave 10 or higher should bring in more Claw spawns. When the time is right, swipe it from a corpse and go to town! Avoid Hording with other plays as they suck up a lot of kills.

If Horde mode isn’t your style, you can join an Arcade match, build up eliminations until you can afford the Claw (6 eliminations/Marcus), and start draining the needle rounds on the enemies.

The best way to stay alive with your precious weapon is to sit back for headshots and enemies trying to cross the field. Be sure to continuously check your flank, so you don’t get mowed down while enjoying the peace and quiet from the back.