The .22 Long Rifle (.22 LR) is a rimfire cartridge featuring a unique heeled bullet with a standard maximum driving band diameter of .2255 inches (5.73 mm). The maximum case length is .613 inches (15.57 mm), and the maximum overall cartridge length is restricted to 1.000 inches (25.40 mm) to ensure compatibility with standard magazines and chambers. The cartridge utilizes a rim diameter of .278 inches (7.06 mm) and maintains a uniform straight body diameter of .226 inches (5.74 mm) from the base to the case mouth. Ammunition for this caliber is most commonly found in 36 grain and 40 grain bullet weights. Exact dimensions and operating pressures can vary slightly depending on manufacturing tolerances and whether you reference American SAAMI specifications or European C.I.P. standards.
.22 LR Dimensions
| Dimension | Specification | Source | Notes |
| Bullet Diameter | .2255 in (5.73 mm) | SAAMI | Heeled bullet design; measured at the external driving band. |
| Case Length | .613 in (15.57 mm) | SAAMI | Maximum case length. |
| Overall Cartridge Length | 1.000 in (25.40 mm) | SAAMI | Maximum overall length for standard chambers and magazines. |
| Rim Diameter | .278 in (7.06 mm) | SAAMI | Maximum rim diameter; contains the priming compound. |
| Rim Thickness | .043 in (1.09 mm) | SAAMI | Critical dimension for proper headspacing. |
| Case Diameter (Base) | .226 in (5.74 mm) | SAAMI | Maximum diameter measured at the base. |
| Shoulder Diameter | N/A | N/A | Straight walled cartridge; no shoulder. |
| Neck Diameter | .226 in (5.74 mm) | SAAMI | Maximum external diameter at the case mouth. |
| Base Diameter | .226 in (5.74 mm) | SAAMI | Uniform with the neck due to the straight walled design. |
| Maximum Pressure | 24,000 psi | SAAMI | C.I.P. maximum is 1,700 bar (approximately 24,656 psi). |
Understanding The .22 LR Dimensions
- Bullet Diameter: The measurement across the widest point of the bullet. For the .22 LR, this is specified as .2255 inches. Unlike most modern cartridges, the .22 LR uses a “heeled” bullet, meaning the rear portion of the bullet is stepped down to fit inside the case, while the exposed front portion is the same width as the outside of the brass case.
- Case Length: The length of the empty brass cylinder from the base to the case mouth, maxing out at .613 inches.
- Overall Cartridge Length (OAL): The total length of the fully assembled round from the base to the tip of the bullet, strictly capped at 1.000 inches. OAL directly influences whether a cartridge will fit into a box magazine or tubular magazine properly.
- Rim Diameter: The diameter of the flange at the very bottom of the case measuring .278 inches. Because this is a rimfire cartridge, this folded rim physically contains the impact sensitive priming compound.
- Rim Thickness: Measuring .043 inches, this is the thickness of the folded rim. This dimension is absolutely critical because the .22 LR headspaces on this rim.
- Case Diameter: The width of the cartridge body. The .22 LR is a straight walled case, meaning the base diameter (.226 inches) and the neck diameter (.226 inches) are identical.
- Maximum Pressure: The peak internal pressure generated when the cartridge is fired. Standard SAAMI limits set this at 24,000 psi to ensure standard blowback actions function safely.
.22 LR Cartridge Dimensions In Inches And Millimeters
For engineers, reloaders, and international shooters, below are the primary .22 LR measurements converted accurately between imperial and metric systems.
| Dimension | Inches (SAAMI Max) | Millimeters (Equivalent) |
| Bullet Diameter | .2255 in | 5.73 mm |
| Case Length | .613 in | 15.57 mm |
| Overall Length | 1.000 in | 25.40 mm |
| Rim Diameter | .278 in | 7.06 mm |
| Rim Thickness | .043 in | 1.09 mm |
| Case Diameter | .226 in | 5.74 mm |
.22 LR Case Dimensions
The .22 LR is defined by a rimmed, straight walled copper or brass case. The official maximum case length is .613 inches (15.57 mm). The base diameter measures .226 inches, and the rim extends slightly wider to .278 inches.
Unlike centerfire cartridges that feature a solid brass web and an extractor groove, the .22 LR utilizes a folded rim design. During manufacturing, the base of the thin brass or copper case is spun to distribute a wet priming compound directly into the hollow outer lip of the rim. Because the case walls are relatively thin to ensure the firing pin can crush the rim, the cartridge operates at a moderate 24,000 psi to prevent the case from rupturing upon ignition.
.22 LR Bullet Diameter
The standardized maximum bullet diameter for the .22 LR is .2255 inches (5.73 mm). The dimension that sets the .22 LR apart from almost all other modern cartridges is its heeled bullet design.
In a standard centerfire cartridge, the bullet slips inside the case mouth, meaning the bullet is narrower than the outside diameter of the brass case. In the .22 LR, the rear “heel” of the bullet is stepped down to roughly .207 inches to fit inside the case. The exposed driving band of the bullet remains .2255 inches wide, which matches the outside diameter of the .226 inch brass case.
The standard .22 LR barrel features a groove diameter of .222 inches and a bore or land diameter of .217 inches. Firing a .2255 inch bullet down a .222 inch groove diameter forces the soft lead bullet to engrave tightly into the rifling, creating the spin necessary for stabilization.
.22 LR Overall Length
The SAAMI maximum overall cartridge length (OAL) for the .22 LR is 1.000 inches (25.40 mm). This number is a hard limit designed to guarantee that the cartridge will feed perfectly through the massive variety of semi automatic, bolt action, and lever action firearms chambered for it.
Typical factory cartridge length varies based on the bullet profile. A classic 40 grain solid round nose bullet often measures extremely close to the 1.000 inch maximum. In contrast, lightweight 36 grain hollow points or 32 grain hyper velocity rounds often measure slightly shorter, sitting closer to .980 inches to ensure proper feeding angles up the feed ramp.
.22 LR Chamber And Cartridge Dimensions
The relationship between the .22 LR cartridge and the firearm chamber is heavily dependent on the rim. The .22 LR cartridge headspaces entirely on the front face of its .278 inch rim.
This means the protruding rim physically stops against the rear face of the barrel chamber. The rim thickness (.043 inches) dictates the exact headspace tolerance. If a firearm has excessive headspace, the firing pin may not strike the rim with enough force to crush the priming compound, leading to a misfire. The chamber itself must fully support the thin case walls. If the cartridge fires slightly out of battery, the unsupported brass will violently rupture.
.22 LR Dimensions vs Similar Cartridges
To understand the .22 LR size profile, it is helpful to compare it against other rimfire cartridges in the .22 caliber family. Note that dimensional similarities do not imply ammunition interchangeability.
| Cartridge | Bullet Diameter | Case Length | Overall Length | Case / Base Diameter | Maximum Pressure | Source |
| .22 LR | .2255 in | .613 in | 1.000 in | .226 in | 24,000 psi | SAAMI |
| .22 Short | .2255 in | .423 in | .695 in | .226 in | 21,000 psi | SAAMI |
| .22 Long | .2255 in | .613 in | .880 in | .226 in | 24,000 psi | SAAMI |
| .22 WMR | .2240 in | 1.055 in | 1.350 in | .242 in | 24,000 psi | SAAMI |
| .17 HMR | .1720 in | 1.058 in | 1.349 in | .242 in | 26,000 psi | SAAMI |
.22 LR vs .22 WMR Dimensions
The .22 Long Rifle and the .22 Winchester Magnum Rimfire (.22 WMR or 22 Mag) are frequently confused, but they are physically very different cartridges.
- Bullet Design: The .22 LR uses a .2255 inch heeled lead bullet. The .22 WMR uses a modern .224 inch jacketed bullet that sits entirely inside the case mouth without a heel.
- Case Width: Because the .22 WMR bullet sits inside the case, the brass case itself must be wider. The .22 WMR base diameter is .242 inches, while the .22 LR base diameter is .226 inches.
- Length: The .22 WMR is significantly longer, featuring a 1.055 inch case and a 1.350 inch overall length, compared to the .613 inch case and 1.000 inch overall length of the .22 LR.
Due to the wider case diameter of the .22 WMR, you cannot safely fire a .22 LR cartridge inside a .22 WMR chamber. The narrower .22 LR case will split or burst upon firing because the wider chamber walls cannot support the thin brass.
.22 LR SAAMI vs C.I.P. Dimensions
Cartridge dimensions and safe pressure limits are governed by SAAMI in the United States and C.I.P. in Europe.
The physical dimensional specifications for the .22 LR are functionally identical between the two governing bodies to ensure global compatibility. SAAMI lists the maximum average pressure for standard .22 LR at 24,000 psi, measured via conformal piezoelectric transducers. C.I.P. lists the maximum pressure for the exact same cartridge at 1,700 bar, which translates to approximately 24,656 psi. Ammunition loaded to SAAMI specs is completely safe in C.I.P. proofed firearms, and vice versa.
.22 LR Bullet Weight And Dimensions
The .22 LR is widely loaded in several common bullet weights, which slightly alter the external bullet profile while keeping the brass dimensions identical.
- 40 grain: The traditional standard weight for target and hunting ammunition. This solid lead round nose bullet typically pushes the cartridge to its maximum 1.000 inch length.
- 36 grain: Extremely common for hollow point hunting rounds. The missing lead from the hollow tip reduces the weight and sometimes results in a slightly shorter overall length.
- 60 grain: Highly specialized subsonic rounds, such as the Aguila Sniper Subsonic, use a massive 60 grain bullet. To maintain the 1.000 inch maximum overall length, these rounds utilize the much shorter .423 inch case from the .22 Short but pair it with a bullet that is physically twice as long.
Bullet weight does not change the standardized external brass case diameter, but radical bullet weights require unique bullet seating depths to ensure the loaded round still cycles safely.
Why .22 LR Dimensions Matter
Understanding the specific .22 LR measurements is essential for several practical reasons.
- Feeding Reliability: The 1.000 inch overall length is the most critical dimension for semi automatic firearms. Ammunition that is manufactured too short or features an aggressive hollow point can crash into the feed ramp instead of gliding smoothly into the chamber.
- Headspace Safety: The .043 inch rim thickness is all that prevents the firing pin from striking the steel barrel face in many designs. Proper rim dimensions ensure reliable primer ignition and safe locking.
- Bore Fouling: Because the heeled bullet is exactingly matched to the case diameter, any deformation of the soft lead driving band during feeding can result in poor accuracy and heavy lead fouling inside the barrel grooves.
Manufacturer Specifications vs Independent Measurements
If you use calipers to measure factory .22 LR ammunition from companies like CCI, Federal, or Winchester, the numbers will rarely match the SAAMI maximum specifications exactly.
SAAMI publishes maximum allowable dimensions to ensure absolute safety and compatibility across millions of firearms. Ammunition manufacturers purposefully produce their cases slightly smaller than these maximums. For example, measuring a factory cartridge and finding a case length of .605 inches or an OAL of .990 inches does not mean the ammunition is defective. It means the manufacturer built in a reliable negative tolerance margin to guarantee the ammunition will load easily into tight match grade rifle chambers.
Common Questions
What are the dimensions of the .22 LR?
The key maximum dimensions are a bullet diameter of .2255 inches, a case length of .613 inches, and an overall cartridge length of 1.000 inches.
What is the .22 LR case length?
The maximum SAAMI case length is .613 inches (15.57 mm).
What is the .22 LR overall length?
The maximum overall length (OAL) is 1.000 inches (25.40 mm).
What is the .22 LR bullet diameter?
The standard heeled bullet diameter is .2255 inches, matching the outside width of the brass case.
What is the .22 LR rim diameter?
The rim diameter measures .278 inches (7.06 mm).
What is the .22 LR case diameter?
The .22 LR is a straight walled cartridge, meaning the case diameter is uniformly .226 inches from the base to the case mouth.
How do .22 LR and .22 WMR dimensions compare?
The .22 WMR is significantly larger in every dimension. It features a wider .242 inch base diameter, a longer 1.055 inch case, and a longer 1.350 inch overall length compared to the smaller .22 LR.
What is a heeled bullet in .22 LR?
A heeled bullet means the rear of the bullet is stepped down to fit inside the case mouth, leaving the exposed front portion of the bullet flush with the outside diameter of the brass case.
What is the maximum overall length of the .22 LR?
The absolute maximum allowed by SAAMI is 1.000 inches to ensure the bullet fits inside standard box and tubular magazines.
What is the .22 LR maximum pressure?
The SAAMI maximum average pressure is 24,000 psi.