Fallout: New Vegas ammunition

Overview
Ammunition or ammo is the term used for expendable ordnance material used in charging firearms of all kinds; as powder, balls, shot, shells, percussion caps, rockets, missiles, energy, etc. The purpose of ammunition is to project force against a selected target or area.

Currently the Pip-Boy 3000 menu displays ammunition of any given type by the combined weight of all rounds of the same type, and not the per round weight.

Other

 * Note: camera film is actually classed as a form of gun ammunition.

Ammunition boxes

 * Note: Weight only applies while playing on Hardcore mode.
 * ¹ Compatible with weapons that use 5.56mm rounds.
 * ² Compatible with weapons that use .357 magnum rounds.

Notable Vendors
These are vendors carrying large amounts of certain ammunition types.
 * .308 round: Daniel Contreras at Camp McCarran and Quartermaster Bardon at Hoover Dam.
 * 12.7mm round: Daniel Contreras at Camp McCarran and Quartermaster Bardon at Hoover Dam.
 * 12 gauge shotgun shell: Quartermaster Bardon at Hoover Dam.
 * 25mm grenade, .50 BMG: Vendortron at Gun Runners, Alexander at 188 Trading Post, and Quartermaster Bardon at Hoover Dam.
 * 40mm grenade: Cliff Briscoe at Novac, Vendortron at Gun Runners, Lacey at Mojave Outpost, Boomer munitions manager at Nellis Air Force Base, and Quartermaster Bardon at Hoover Dam.
 * Flamer fuel: Chet at Goodsprings and Johnson Nash at Primm
 * Great Khan armorer at Great Khan armory has large quantities of all ammunition except missiles and flamer fuel
 * HE and HV missiles: Vendortron at Gun Runners.

Loading
To load different ammunition, go into the Pip-boy, scroll to the "Ammunition" section and select from the list any compatible ammunition type for the currently equipped weapon. Outside of the Pip-boy, use the hot-key to switch ammunition types for the currently equipped weapon.

Bugs

 * The pop-up describing ammunition that appears when selecting the "Ammo" tab in the Pip-Boy for the first time states that armor piercing rounds do slightly more damage than standard rounds.
 * When transferring ammunition to a companion in hardcore mode and you get a message that the transfer will overload them (which is correct), try reducing the amount you're giving them at once. For instance, Boone might not like you lumping 200 microfusion cells on him at once, so try maybe 20 or 50 at a time. You can keep trickling them in at this reduced amount until they're all transferred. You can then proceed to transfer in different ammunition types in the same trade session, but once you exit, you'll have to take some weight off him to bring him under 220WG to 'overload' him with ammunition again. Note: On the character wheel, it will still display his maximum full weight (220/220 WG) though what he's truly carrying could now be far exceeding this.