about . Long Rifle, M24 (Jacketed Bullet), propellant: 2.5 gr smokeless, bullet: 40.5 gr, overall length: . The first type specifies standard or target velocity .22 LR while the second is common high velocity commercial ammo. While these soft lead round nose bullet types were suitable for training or target practice, they are not legal for use in a war zone. Since .22 LR air crew survival weapons would probably be used in a war zone and could be used for defense, the M24 round is loaded with a hard lead-antimony alloy core bullet with a gilding metal jacket. Tracer Tracer ammunition is also available in .22 Long Rifle rimfire. Cartridge construction The traditional .22 rimfire cartridges (BB, CB, short, long, extra long, and long rifle) differ in construction from more modern cartridges in the way the bullet is constructed and held in the case. Bullets for traditional .22 rimfires are the same outside diameter as the case but are constructed with a narrower cupped "heel" on the base of the bullet which is inserted into the case. The case mouth is then crimped around the heel, leaving exposed the majority of the bullet bearing surface that contacts the barrel of the gun. The bearing surface of .22 rimfire bullets is often lubricated and the surface is exposed to contamination. This was a common design in the early black powder cartridge era. In later cartridges including the .22 WRF and .22 WMR rimfires and modern centerfires, the bullet body is a uniform diameter and the bearing surface is inserted completely within the neck of the cartridge case, held in place by tension from the case neck around the bullet bearing surface (in some cartridges the case mouth may also be crimped into a cannelure (groove) in the bullet). The heeled bullet cartridge is considered weaker than the uniform diameter bullet cartridge which encloses the bearing surface of the bullet within the cartridge neck. Overall reliability of heeled bullet rimfire ammunition is high, but it is lower than the reliability of most centerfire ammunition. Cartridge length The .22 LR uses a straight-walled case. Depending upon the type and the feed mechanism employed, a firearm that is chambered for .22 LR may also be able to safely chamber and fire the following shorter rimfire cartridges: .22 BB, in cap, short, and long lengths .22 CB, in cap, short, long, and long rifle