presents itself. A common doctrine is "shoot one, load one": load a shell immediately after every shot (when this does not jeopardize the operator's safety), to ensure that the shotgun is fully loaded at all times; this ensures that the operator has a full magazine at their disposal in case of emergencies when they may not be able to reload in between shots. A pistol is also advised as a backup weapon, should the operator empty the magazine and not have time to reload. A sling to carry the shotgun is essential if it is to be used in conjunction with another weapon, so that the shotgun may be readily accessible. The bulk and weight of shotgun ammunition also limits its utility as a general-issue weapon. Weight per 100 rounds of an average 12-gauge 00-buck shell is ; for an average .223/5.56 round, weight per 100 rounds is about or a 3.8:1 weight ratio of 12-gauge buckshot and 5.56×45mm. This means just eight 12-gauge buckshot shells weigh approximately the same () as thirty 5.56×45mm rifle cartridges. While an individual soldier can easily carry several hundred rifle or pistol cartridges in box magazines, only a few dozen shotshells can be carried practically. Effectiveness A Joint Service Combat Shotgun Program report on the lethality of shotguns in war states, in support of the use of the shotgun in warfare, "the probability of hitting a man-sized target with a shotgun was superior to that of all other weapons", and goes on to support this with statistics compiled by the British from the conflict in Borneo in the 1960s - Operation Claret. The buckshot typically used in a combat shotgun spreads out to a greater or lesser degree depending on the barrel choke, and can be effective at ranges as far as 70 m (75 yards). The delivery of the large number of projectiles simultaneously makes the shotgun the most effective short range weapon commonly used, with a hit probability 45% greater than a sub-machine gun (5-round burst), and twice as great as an assault rifle (3-round burst). While each pellet is only roughly as effective as a small caliber handgun round, and offers very poor penetration against an armored target, the multiple projectiles increases the likelihood of one or more peripheral wounds. A number of compromises are involved in choosing a shot size: Smaller pellets lose velocity more rapidly and penetrate the target