So what exactly is the difference between the .22LR and .223 cartridges? Both can be fired out of rifles, and both can be fired out of pistols. Both have been used historically by civilian and military shooters. Both can be used for hunting (.22LR for animals such as rats, squirrels, rabbits, ground hogs; .223 for larger animals including coyotes, and in some states deer). Both are extremely popular rounds — .22LR is by far the most popular rimfire cartridge, and .223 is near the top (if not at the top) of the list of most popular centerfire cartridges.
Well, there’s one difference right there. Rimfire is an older design, which for the most part has been replaced with centerfire. Almost all ammunition used now is centerfire. With rimfire, the firing pin impacts on the rim of the case. With centerfire, the firing pin impacts in the center of the case. Fairly self explanitory. But it doesn’t really explain the differences between the two cartridges very well.
As mentioned above, rimfire is an older technology than centerfire. The .22LR cartridge was introduced in 1887, while the .223 cartridge was designed in 1964, specifically for use in the M-16 rifle.
Nearly a century separates the two cartridges, but what makes them different? Size-wise, the newer cartridge is slightly larger. The caliber of the cartridge measures the diameter (in inches). So the newer cartridge is 0.003″ larger in diameter — who cares? A human hair is from 0.003″ to 0.005″ in diameter. Is such a slight increase in diameter really going to make a difference?
Below is a cardboard pizza box shot with a .22LR bullet. The entry point can be seen on the left and the exit on the right. A penny is used for reference.