Quicksilver Bullet - Bloodborne Wiki

Quicksilver Bullets are a stackable, consumable item used as ammunition for firearms and hunter tools. They are also used in certain special attacks and tricked attacks for some weapons.

Special bullets used with hunter firearms.

Ordinary bullets have no effect on beasts, and so Quicksilver Bullets, fused with the wielder's own blood, must be employed.
The strength of Quicksilver Bullets depends greatly upon the wielder's bloodtinge.

Acquisition

Quicksilver Bullets can be acquired as a common drop from most overworld and Chalice Dungeon enemies, specifically those wielding firearms or using projectiles. They may also be purchased from the Bath Messengers in the Hunter’s Dream. Their cost to purchase from the Bath Messengers is dependent on the current Moon Phase.

Usage

As the hunter uses firearms and hunter tools. their bullet count will decrease accordingly. Most firearms cost 1 Quicksilver Bullet per shot, but more powerful weapons such as the Cannon are much more bullet-hungry, consuming 12 bullets per shot. Similarly, hunter tools with less damage or utility such as Augur of Ebrietas cost only 1 Quicksilver Bullet per cast, with more powerful tools such as A Call Beyond costing 7 bullets per cast.

Price

Game start: 160 Blood Echoes
Upon entering Cathedral Ward: 240 Blood Echoes
Upon inspecting the skull of Lawrence and triggering Nightfall: 320 Blood Echoes
After defeating Rom, the Vacuous Spider, and triggering the Blood Moon: 400 Blood Echoes

Blood Bullets

The hunter may at any time convert a Blood Vial into 5 Blood Bullets, a variant of Quicksilver Bullets, by pressing up on the D-pad. This will consume 30% of the hunter's current health, and cannot be performed should the hunter's health fall below the 30% threshold. Activating the Blood Bullet conversion will always reset the number of Blood Bullets in the hunter's inventory to 5, regardless of how many they currently have equipped.