The exact .22 LR (Long Rifle) bullet diameter is 0.223 inches, which converts to 5.66 millimeters. While .22 LR ammunition is available with different bullet weights and velocities, the cartridge’s nominal projectile diameter remains consistent across standard factory loads. This measurement refers specifically to the width of the bullet itself, which differs from the internal dimensions of the barrel. Specifically, a standard .22 LR firearm utilizes a narrower bore diameter of 0.217 inches and a groove diameter of 0.222 to 0.223 inches to ensure a tight gas seal upon firing.
.22 LR Bullet Diameter
| Specification | .22 LR |
| Nominal Bullet Diameter | 0.223 inches |
| Bullet Diameter In Inches | 0.222″ to 0.223″ |
| Bullet Diameter In Millimeters | 5.64 to 5.66 mm |
| Groove Diameter | 0.222 – 0.223 inches |
| Bore Diameter | 0.217 inches |
| Typical Bullet Weights | 29 gr to 40 gr |
| Case Length | 0.613 inches |
| Overall Cartridge Length | 0.985 inches |
| Maximum Pressure (SAAMI) | 24,000 PSI |
What Is The .22 LR Bullet Diameter?
The .22 LR bullet diameter is the physical width of the unfired projectile seated in the cartridge case. Introduced in 1887 by J. Arms Corporation and Stevens Arms, the .22 Long Rifle is the most popular and widely consumed ammunition cartridge in the world. Unlike centerfire cartridges where the primer is centered in the case base, the .22 LR is a rimfire cartridge, meaning the priming compound is spun directly into the rim of the brass case. The bullet is a “heeled” design, meaning the rear portion of the bullet that fits into the case has a reduced diameter matching the inside of the case, while the exposed front part of the bullet measures a true 0.223 inches.
.22 LR Bullet Diameter In Inches
According to the official Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) specifications, the .22 LR bullet diameter in inches is standard at 0.223 inches (with a tolerance range typically between 0.222″ and 0.223″). Most standard lead round nose or copper-plated hollow point bullets adhere strictly to this sizing.
.22 LR Bullet Diameter In Millimeters
For those using metric measurements, the .22 LR bullet diameter in mm is approximately 5.66 mm. Because 1 inch equals 25.4 millimeters, multiplying a 0.223-inch bullet by 25.4 yields 5.6642 mm, which rounds cleanly to 5.66 mm (frequently designated internationally as 5.6×15mmR).
.22 LR Bullet vs Bore Diameter
A common point of confusion is the difference between the bullet’s width and the barrel’s internal dimensions. The .22 LR bore diameter is 0.217 inches. The bore diameter measures the distance directly across the “lands” (the raised portions of the rifling inside the barrel). The unfired .22 LR projectile diameter (0.223″) is deliberately wider than the bore so the soft lead or copper-washed rifling can firmly bite into the bullet, imparting the stabilizing spin required for accuracy.
.22 LR Groove Diameter
The .22 LR groove diameter measures between 0.222 and 0.223 inches. The groove diameter measures the distance across the deepest cuts inside the rifled barrel. When the 0.223-inch bullet is fired, it swages into the barrel and completely fills the grooves. This creates a tight pressure seal that traps the expanding powder gases directly behind the bullet, preventing velocity loss and maintaining consistency.
.22 LR Bullet Weights
While the cartridge diameter is fixed, you can select different projectile masses depending on your application. The .22 LR bullet weight typically ranges from lightweight 29-grain high-speed or hyper-velocity loads up to standard 40-grain solid lead rounds and heavy 45-grain subsonic loads designed for suppressed shooting. Changing the weight alters the bullet’s length, velocity, and trajectory, but the outer diameter remains fixed.
Bullet Diameter vs Other Cartridges
Shooters must be careful when comparing caliber names, as small-bore cartridge names frequently vary slightly from their actual physical dimensions. Here is how the .22 LR compares to other small-caliber rounds:
| Cartridge | Bullet Diameter | Diameter In mm |
| .22 LR | 0.223″ | 5.66 mm |
| .22 WMR (Magnum) | 0.224″ | 5.69 mm |
| .223 Remington / 5.56 NATO | 0.224″ | 5.70 mm |
| .22 Short | 0.223″ | 5.66 mm |
| .17 HMR | 0.172″ | 4.37 mm |
| 9mm Luger | 0.355″ | 9.02 mm |
Notice that the .22 LR shares nearly identical projectile dimensions with centerfire heavy hitters like the .223 Remington (0.224″), though the .22 LR case is vastly smaller, rimfire-primed, and operates at a fraction of the power.
Bullet Weight
Ammunition manufacturers produce an enormous variety of .22 LR loads tailored for target shooting, small game hunting, and plinking.
| Bullet Weight | Example Load | Bullet Type | Advertised Velocity |
| 29 grain | CCI Velocitor | Hollow Point (Hyper-Velocity) | 1,435 fps |
| 36 grain | Federal Copper-Plated | Hollow Point (High-Velocity) | 1,260 fps |
| 40 grain | CCI Standard Velocity | Lead Round Nose | 1,070 fps |
| 45 grain | CCI Quiet-22 | Lead Round Nose (Subsonic) | 710 fps |
Velocities represent typical factory test barrel data, generally from a standard rifle barrel.
Dimensions
To understand how the rimfire cartridge fits into rifle chambers and tubular or box magazines, here are the complete SAAMI-verified .22 LR dimensions:
| Dimension | Measurement |
| Bullet Diameter | 0.223″ |
| Groove Diameter | 0.222″ – 0.223″ |
| Bore Diameter | 0.217″ |
| Case Length | 0.613 inches |
| Overall Length | 0.985 inches |
| Base / Rim Diameter | 0.226 inches |
| Maximum Pressure (SAAMI) | 24,000 PSI |
.22 LR vs .22 WMR
Because both cartridges are popular rimfire rounds designed for small-caliber shooting, many shooters frequently compare the .22 LR and .22 WMR (.22 Winchester Magnum Rimfire).
Despite both being rimfire rounds, they are entirely incompatible and built for different performance tiers:
- Case Size: The .22 WMR features a significantly longer (1.055 inches) and wider case compared to the tiny .22 LR case (0.613 inches).
- Bullet Diameter: The .22 WMR uses a slightly wider bullet measuring 0.224 inches, compared to the 0.223-inch bullet of the .22 LR. Furthermore, .22 WMR bullets are typically jacketed, whereas .22 LR bullets are usually bare lead or copper-washed.
- Power and Velocity: The .22 WMR operates at much higher pressures and pushes bullets at velocities exceeding 2,000 fps, offering flatter trajectories and more energy at 100+ yards than a standard .22 LR.
You can never fire a .22 WMR cartridge in a firearm chambered for .22 LR, as the casing is too large and the pressures are too high.
.22 LR Bullet Diameter: Exact Measurement
The exact .22 LR bullet diameter is 0.223 inches, or 5.66 millimeters.
While the actual projectile measures 0.223 inches across, it is pushed through a barrel with a 0.217-inch bore diameter and a 0.222–0.223-inch groove diameter. Because standard .22 LR bullets are constructed of soft lead, they easily swage down to fit the barrel’s rifling perfectly. This creates a reliable gas seal behind the projectile, preventing the 24,000 PSI of expanding gases from blowing past the bullet while ensuring it stabilizes accurately for target shooting and small game hunting.
FAQs
What is the bullet diameter of .22 LR?
The nominal bullet diameter is 0.223 inches.
What is .22 LR bullet diameter in mm?
In metric measurements, the diameter translates to 5.66 mm.
Is .22 LR actually .22 inches?
Yes. The actual projectile measures 0.223 inches across, making it a true .22-caliber round.
What is the bore diameter of .22 LR?
The barrel’s internal bore diameter (measured land-to-land) is 0.217 inches.
What is the groove diameter of .22 LR?
The barrel’s internal groove diameter (measured groove-to-groove) is 0.222 to 0.223 inches.
What bullet weights are available for .22 LR?
Factory loads typically range from light 29-grain hyper-velocity rounds up to standard 40-grain solid lead bullets and 45-grain subsonic loads.
What is the case diameter of .22 LR?
The case is a rimfire design measuring approximately 0.226 inches at the rim, tapering slightly down to 0.223 inches along the straight-walled brass tube.
How does .22 LR bullet diameter compare with .223 Remington?
The .22 LR (0.223″) and .223 Remington (0.224″) have almost identical bullet diameters, but the .223 Remington is a high-powered centerfire rifle cartridge with vastly more energy and velocity.