Ammunition

Cryo Rounds

 * Freezing effects from the Cryolator or Cryo Rounds, now work on most enemies (to varying degrees)
 * Consecutive hits on tougher enemies, only partially chill them, and still cannot completely freeze them
 * Consecutive hits on weaker enemies can still freeze them solid as usual
 * Some creatures now have Cryo Resistance (see further below)
 * Creatures that have Cryo Resistance, are often susceptible to taking extra fire damage (useful when using Awareness)

API Rounds

 * Armor Piercing Incendiary
 * There is no more armor penetration on perks and weapon receivers, its only based on the ammo now
 * API Rounds loaded into weapons will grant armor penetration based on the weapon and the caliber
 * .50 API = -100% Armor Penetration
 * .308 API = -85% Armor Penetration
 * .45 API = -50% Armor Penetration
 * 5.56 API = -50% Armor Penetration
 * Some API rounds can shoot through walls and body parts based on the weapon and the caliber
 * Lower caliber rounds have a lower hit chance in VATS to hit through walls and body parts
 * All API rounds are now more expensive to craft, and require Tungsten alloy
 * There are more sources of Tungsten alloy in loot/junk now
 * Tungsten Rod: scraps into 2 tungsten alloy (located rarely on some vendors or loot)

HE Rounds

 * High-Explosive Rounds
 * These rounds explode on contact damaging everything in a small area for 20 damage per hit
 * These rounds have a 20% chance of knocking down the main target you hit directly
 * The knockdown effect does not work on larger enemies
 * These rounds do not pierce armor (they do not have the internal mechanics that API rounds have to penetrate armor, only raw explosive material)
 * HE rounds are only available on weapons that use .50 and 12.7mm
 * You can craft them in the Weapon Lab

RAD Rounds

 * Adds radiation damage, but reduces ballistic damage
 * Irradiated rounds are only available on weapons that use .38 rounds

Pulse Rounds

 * Adds energy damage, but reduces ballistic damage
 * Deals +50% damage against Robots and Synths
 * Pulse rounds are only available on weapons that use .44 rounds
 * Has a graphical EMP effect upon impact

VENOM Rounds

 * Adds 40 poison damage over 10 seconds, but reduces ballistic damage
 * VENOM rounds are only available on weapons that use .44 rounds
 * Has a graphical green cloud effect upon impact

Ammo Boxes

 * Standard/Raider Ammo Boxes: Most types of ammo can now drop earlier
 * Standard/Raider Ammo Boxes: A small amount of bonus ammo is more random now (slightly less on average)
 * Standard/Raider Ammo Boxes: Increased chance of getting ammo scrap instead of generic junk

Ammo Crafting

 * All ammo is now sorted into multiple categories: Ballistic, Energy, Contracted Work, Imported
 * Most ammo crafting recipes now give ammo packs, so you can see how many rounds you're getting per craft
 * Ballistics, Science and Magazines grants access to ammo crafting recipes
 * crafting Materials you should focus on: Aluminum, Copper, Lead, Smokeless Powder and many more

Ammo Field Switching

 * You can now use a device called the "Weapon Toolkit" to switch ammo and firing modes on certain weapons
 * The device is located in the AID tab, and can be assigned to your favorites bar
 * Certain ammo types may require an "Advanced Conversion Kit"

= Common Types = Ammo in Horizon follows different tiers. This is a general ranking of how powerful each caliber is. Note that the more powerful a caliber, the more it weighs and the more expensive it is to buy it or craft it. A rule of thumb to keep in mind is that the more Smokeless Powder a weapon uses, the more damage it does. Weapons also have three tiers of ammo that can be chambered. The first tier is common, light, low damage but with added fire rate. Next is the mid tier, which is usually what the caliber was in vanilla Fallout 4, and as such, has damage and fire rate compared to vanilla. Lastly is high tier, which is with expensive ammo that does a lot of damage at a reduced fire rate.

.22 LR
.22 LR rounds are now dirty rounds that deal 4 Rad damage but have reduced ballistic damage and reduced recoil
 * .22 LR RAD

.38

 * .38
 * .38 RAD

5mm

 * 5mm
 * 5mm RAD
 * 5mm CRYO
 * 5mm API

9mm

 * 9mm rounds are now hollow points (HP) and deal 4 bleeding damage over 10 seconds, but have reduced range
 * 9mm ammo is properly named "9mm JHP"
 * bleed damage takes damage resistance into account
 * 9mm

10mm

 * 10mm
 * 10mm CRYO

.357

 * .357

.45

 * .45
 * .45 CRYO
 * .45 API

12 Gauge

 * 12 Gauge
 * 12 Gauge Terror Shells
 * 12 Gauge Mind Cloud
 * 12 Gauge RAD
 * 12 Gauge CRYO
 * 12 Gauge Double Slug
 * 12 Gauge API

.44

 * .44
 * .44 VENOM
 * .44 PULSE

12.7

 * 12.7
 * 12.7 HE

5.56

 * 5.56
 * 5.56 API

.308

 * .308
 * .308 API

.45-70

 * .45-70

7.62

 * 7.62
 * 7.62 API

2mm EC

 * 2mm EC
 * 2mm EC AP

.50
.50 API rounds used in an LMG only provides -75% AP
 * .50
 * .50 API
 * .50 HE

Fusion Core

 * This option is toggled in the Field Kit instead of an item
 * Nuclear Physicist 3 no longer automatically grants Fusion Core ejections

Fusion Cells

 * Fusion Cell
 * Fusion Cell MX
 * Heavy Fusion Cell
 * Heavy Fusion Cell MX

Plasma Cartridge

 * Plasma Cartridge
 * Fiery Plasma Cartridge

VICE Cartridge

 * 2mm VICE Cartridge
 * 2mm VICE MX Cartridge

Special

 * Alien Blaster
 * Gamma Rounds

Fuels

 * Cryo Cells
 * Flamer Fuel

40mm

 * 40mm Grenade
 * 40mm Venom Slug
 * 40mm Cryo
 * 40mm Incendiary
 * 40mm Irradiated Shotgun
 * 40mm Heated Flechette
 * 40mm Pulse
 * 40mm Plasma
 * 40mm Mininuke
 * 40mm RPG
 * 40mm RPG API
 * 40mm RPG Seeking

Missiles

 * Missile
 * Missile API
 * Missile (Nuclear)

Bolts

 * Bolt: Standard damage
 * Bolt (Cryo): Adds cryo damage and a chance to slow or freeze targets, reduced ballistic damage
 * Bolt (Heated): Adds fire damage, reduced ballistic damage
 * Bolt (Shock): Adds energy damage, increased damage against robots/synths, reduced ballistic damage
 * Bolt (Explosive): Area damage on impact, chance to knockdown some targets
 * Bolt (AP): Increased damage, -50% armor penetration
 * Bolt (Whisper): Emmits no sound, adds Rad damage, reduced ballistic damage
 * Bolt (Venom): Emmits no sound, adds Poison damage, reduced ballistic damage