10mm

10mm is an ammunition type found in Fallout, Fallout 2, Fallout 3, Fallout: New Vegas, Fallout 4, Fallout 76, and Van Buren.

Background
Before the War, the powerful 10mm Automatic round was the standard ammunition for the Bureau of Alcohol, Drugs, Tobacco, Firearms and Lasers and other federal agencies, while the military was more reliant on experimental energy weapons (although it remained the round of choice for conventional pistols and submachine guns). The G brand of ammunition was one of the most popular, offering excellent centerfire cartridges for a variety of applications.

10mm Auto, full metal jacket (FMJ)


The basic 10mm Automatic round is a standard full metal jacket bullet: A soft metal core surrounded by a jacket made from tougher metal. This allows for higher muzzle velocities and greater damage, as well as increased performance against armor. The increased damage is reduced somewhat by the fact that the metal jacket limits the expansion, resulting in less kinetic energy transferred to the target.

10mm Auto, armor piercing (AP)


A softer metal jacket covers a dense penetrator, while the bullet is loaded with a higher powder load, leading to improved muzzle velocity. However, improved performance against armored targets leads to impaired performance against softer targets, as the higher velocity reduces the amount of kinetic energy transferred to the target on impact.

10mm Auto, jacketed hollow point (JHP)


A hollow point 10mm bullet, where the hard metal jacket is applied specifically to increase bullet strength and create a middle ground between damage potential and penetration.

10mm Auto, hollow point (HP)


10mm hollow point rounds feature a pit or a hollowed out shape at the tip of the bullet. As a result, the bullet expands upon impact, delivering more kinetic energy to the target and disrupting tissue more extensively. However, this same property also leads to dramatically reduced penetrative power, as the bullet will be stopped by armor more easily due to its properties.

Behind the scenes

 * Source for the above statement: DAC