can be efficiently fed by an en-bloc clip, external magazine, or stripper clip. The self-loading design was a successor to earlier rifles that required manual cycling of the weapon after each shot, such as the bolt-action rifle or repeating rifles. The ability to automatically load the next round results in an increase in the rounds per minute the operator can fire. Advantages The primary advantage of self-loading rifles is the possibility of increasing the number of effective shots fired within any given time period by avoiding the necessity for changing the aiming position of the rifle to manually chamber new cartridges. The actual number of hits per unit of time depends upon the magazine capacity and the availability of detachable magazines, but semi-automatic rifles can typically more than double the number of hits from comparable manually-loaded rifles at close range and increase the number of hits by about 50 percent at longer distances which require more precise aiming. Firing for prolonged periods may increase this advantage as the manual-loading process can cause fatigue. The additional weight of springs and fittings using a portion of the cartridge energy to reload self-loading rifles have the additional advantage of reducing recoil. Disadvantages The self-loading mechanism tuned for cartridges of specified dimensions and power may fail to reload dirty or bent cartridges that will otherwise fire satisfactorily. The self-loading mechanism may fail to extract empty low-power cartridge cases useful for training, and high-power cartridges useful at longer ranges may damage the self-loading mechanism. Some self-loading rifles require externally lubricated cartridges vulnerable to dirt adhesion. Any reliability problems causing failure of the self-loading mechanism to function as designed may eliminate the advantage of increased hits per unit of time, and may actually reduce the comparative rate of fire below what is possible with manually-loaded rifles if the self-loading rifle is not designed for convenient manual-loading. The United Kingdom regarded the reliable rate of fire from manually-loaded rifles to be nearly as high as self-loading rifles as recently as World War II. Semi-automatic rifles are uniquely susceptible to slamfire malfunctions caused by abrupt cartridge acceleration during self-loading. Slamfire discharges are unlikely to hit the target, and may cause collateral damage. The time required for changing or reloading magazines can weaken the effectiveness of a rifle, as it imposes an effective duration limit on the continuous rate of fire of any rifle. High-capacity magazines increase the weight