Over all length OAL - Definition

Handloaded cartridges as well as commercially available cartridges normally are created with a maximum length standardized by SAAMI (Sporting Arms and Ammunition Manufactures' Institute). This over all length (OAL) is measured from the base of the brass shell casing to the tip of the bullet, seated into the brass case. A cartridge's OAL may be shorter than the maximum standard or be at the standardized maximum (and sometimes longer: read on). Maximum OAL can be dictated by the need to fit into a box magazine of standard manufacture. For example, the .223 Remington cartridge, when loaded for use in the AR-15 rifle (or the military's M-16 rifle), has to fit into the removable box magazine for that rifle. This dictates that the cartridge maximum OAL be no greater than 2.260". However, for competition purposes during off-hand and slow fire prone match stages, the .223 Remington (AKA the 5.56x45 NATO) is loaded one cartridge at a time into the rifles' receiver. This allows for these cartridges to be longer than the standardized 2.260" SAMMI Maximum OAL. These cartridges can be safely loaded to a length that has the ogive portion of the bullet just touching the rifle's lands. Many competitive shooters will make these cartridges 0.005" less than this truly maximum allowable OAL, for the sake of safety. It is desireable to have these single loaded cartridges have as little bullet jump as possible before the bullet's ogive begins to be engraved by the rifle's lands. This minimized bullet jump increases the accuracy of the rifle, all else being equal. This practice of long-loading a cartridge must be adjusted for each individual rifle, since there are variations from rifle to rifle as to how far down the barrel the rifling begins.