Set all weapons to Cyclones and chase lots of ammo boxes into a corner. Switch to secondary function and keep tapping the Z button for a few hours. You can on average do about 15k - 20k every half hour.
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Set all weapons to Cyclones and chase lots of ammo boxes into a corner. Switch to secondary function and keep tapping the Z button for a few hours. You can on average do about 15k - 20k every half hour, 30k an hour, or 15 hours to complete 450k