.22LR Round

The .22LR round is a type of ammunition in Fallout: New Vegas.

Characteristics
The .22LR is a very low powered round, especially when compared to the more common 5.56mm, .308, .44, or .45 Auto cartridges that are also used in the post-war world. The .22LR was used as a commercial small game hunting round, but wasn't as common on the East Coast as the .32. It has a self-contained "rimfire" primer and thus cannot be broken down to gain small pistol primers, nor can it be crafted.

Weapons using this ammunition

 * Silenced .22 pistol
 * Silenced .22 SMG

Breakdown
Breaking down a standard .22LR round yields:

.22LR, hollow point
Hollow point bullets mushroom and break up on impact, causing massive trauma on fleshy, unarmored targets. However, this also means they break up when they hit things like armor plating, drastically reducing the weapon's penetrating power.

.22LR, plinking
Plinking is an onomatopoetic name, referring to the metallic "plinking" sound of the ammunition as it hits tin cans or other, similar objects. Though less harmful than standard .22-caliber ammunition, plinking ammunition can usually be found in abundance. A single box of .22LR plinking ammunition will spawn 100 rounds when added to the player character's inventory.

.22LR round (junk)
The Junk Rounds perk from the Dead Money add-on was at one point intended to create ammunition of a special subtype, called "junk" or "JNK", these rounds all provided the same modifiers regardless of caliber: x 0.75 to damage and 1.5x to condition. The rounds still remain present in game files but are not utilized within the game itself, and if obtained cannot be used in any weapons, even those chambered for the correct caliber.

The presence of .22LR-caliber junk rounds indicates that the perk was to provide a recipe for crafting .22LR rounds, though the final version of the perk does not include one.

Behind the scenes
During development, the varmint rifle was meant to be chambered for the .22LR round, which would have made the ammunition much more commonly available. However, the inherent reduced limb damage penalty for .22LR rounds (prior to patch 1.3.0.4xx) made the weapon so unpopular that "no one wanted to use it", according to J.E. Sawyer. The weapon was changed to a 5.56mm/.223 weapon instead.