Heavy Caliber

Heavy Caliber increases damage of primary weapons (excluding shotguns) at the cost of reduced accuracy by 15% and -5% per rank, at a maximum of 165% and -55% at rank 10, respectively.

Trivia

 * When it was first released, Heavy Caliber increased recoil as well as damage. However the recoil penalty did not affect recoilless weapons (Flux Rifle, Ignis, Synapse, Paris, Lanka, among others), effectively acting as another instance of Serration. This was confirmed to be unintentional in Warframe Prime Time - Episode 2 (9:40). The mod's penalty was changed in Update 10.4.