JHP

A Jacketed Hollow Point, or JHP, bullet is designed to expand when it hits a target. The bullet's nose, rather than being pointed, is recessed (hence "hollow point"). When a JHP bullet penetrates soft tissue, the lead around this cavity is forced outward, causing the bullet to "mushroom," widening its diameter and resulting in a wider wound channel. However, the hollow cavity makes for very poor armor penetration, as the hollow cavity will cause the bullet to flatten prematurely upon hitting an hardened target, causing it to minimally penetrate. In Fallout and Fallout 2, this is reflected by having JHP bullets do more damage to a target than a FMJ round, but having sub-par armor penetration. This means that although you may hit a target for a large amount of damage, the target's armor may very well absorb a great deal of, if not all, damage.

Inconsistancy over effectiveness
While the JHP rounds are designed to be ineffective against armored targets and AP rounds would be ineffective against fleshy targets, they aren't. This is best observed while fighting the assault rifle-toting gaurds in Vault 15 in Fallout 2. Both rifles are initially loaded with 5mm JHP, and deal about 22 points of damage in a mid-ranged burst against Combat Armor. However, the guards only carry 5mm AP to reload with. Subsequent bursts from the same distance often fail to deal any damage at all.

Types of ammo

 * 10mm JHP
 * 5mm JHP
 * .44 JHP