Cryofreeze is an alternate Pack-a-Punch ammo-type found in Call of Duty: Black Ops 4, and it has a chance to be applied to an upgraded weapon when placed in the Pack-A-Punch Machine again. It costs 2500 points initially, but lowers to 1500 after upgrading your weapon 4 times.
Cryofreeze ammo often slows down zombies with an ice effect, similar to Winter's Wail but much less powerful. On occasion, Cryofreeze ammo will cause an icy explosion, eliminating most zombies in its vicinity. Cryofreeze ammo is super effective against Poison Catalyst zombies, causing them to explode in a high-velocity blast.