JHP



A jacketed hollow point (JHP) bullet is designed to cause severe damage, more than normal ammunition, by expanding on impact with its target. In Fallout, Fallout 2, and Fallout Tactics, this is reflected by having JHP bullets do more damage to a target than a FMJ round, but having less-than-standard 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.

Characteristics
They were designed in an attempt to reduce collateral damage, as their penetration is impaired by the function of the hollow cavity. The bullet's nose, rather than being pointed, is recessed (hence "hollow point"). Unlike regular hollow-point ammo, JHP bullets are coated with a harder metal known as the "Jacket" or "Plate". This is to increase bullet strength and an effort to protect the barrel of the gun from lead residue/cast-off and striping. When a JHP bullet penetrates soft tissue, the lead around the hollow cavity is forced outward, causing the bullet to "mushroom" and fragment, increasing 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 a hardened target, causing minimal penetration.

Inconsistency over effectiveness
While the JHP rounds are designed to be ineffective against armored targets and AP rounds are ineffective against fleshy targets, they aren't. This is best observed while fighting the K-112 assault rifle-toting guards 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 carry only 5mm AP to reload with. Subsequent bursts from the same distance often fail to deal any damage at all.