Bolts

Bolts are the ammunition for Geralt's crossbow. The plain bolt is endless, and seven special types change what a shot does: fire, bleeding, armour piercing or blunt force. The Witcher 3 has 14 variants, most of them in a crafted and a bought form.

Combat

Pros

The plain Bolts never run out and can be neither sold nor dropped, so the crossbow always has something loaded.
Underwater the game loads harpoon bolts on its own.
Every bolt deals silver damage as well as its own, so the same quiver works on monsters.
A diagram makes 20 at a time.

Cons

Only one type is loaded at once.
Special bolts run out, and the better bought variants open at a blacksmith only from a set level.

Builds

Bolts matter most in a crossbow build around the Blood and Wine mutation Cat Eyes, which makes bolts pierce and stun or knock down. For everyone else they are a utility: the right bolt to drop a flyer or open a fight.

Fire. The Exploding Bolt, up to 18-22 fire damage in its Relic form.
Bleeding. The Broadhead Bolt bleeds every target it hits for 15 seconds; the Tracking Bolt for 120.
Armour. The Precision Bolt adds armour piercing, up to +15 in its bought form.
Blunt. The Blunt Crossbow Bolt swaps piercing for bludgeoning damage.

Best Bolts

Build	Bolt	Key Figure
Hardest hitter	Exploding Bolt	18-22 fire damage
Bleeding	Broadhead Bolt	100% bleeding chance
Long bleed	Tracking Bolt	Bleeding for 120 seconds
Armor piercing	Bolt with Bait	+100 armor piercing, tied with the Tracking Bolt

Notes

Crafted variants come from diagrams at blacksmiths in stacks of 20; the bought variants are often stronger and appear in shop stock from a set level, for example the Relic Exploding Bolt from level 25.
Éibhear Hattori in Novigrad and the blacksmith in the Kaer Trolde citadel stock most of the stronger bought bolts.