IF IT HAD TRACKS A GUN AND ARMOR IT WAS USED AS A 'TANK'USA ground forces seemed to have a pragmatic concept that anything with tracks, armor, and a gun was used as a tank. While this was sometimes unwise, it often proved successful and thus was encouraged. The M-10 and M-36 gun motor carriages used by USA tank destroyer units were designed with the secondary role of mobile artillery if no tanks were available to fight. There are pictures of M-10s with stacks of ammo tubes around them from this use (and also pictures of Shermans with stacks of ammo around them from being used like this). The M-10 and M-36 were not given .30-caliber coaxial nor bow machine guns, extremely useful for fending off infantry - perhaps as a cost cutting step or to save space. This also hindered their use in ground support by reducing their ability to drive off hostile infantry - and given the open roof of their turrets, that was a major concern. (One might think the designers purposefully left out the .30s to try to prevent their use as tanks.) And yet they were used for infantry support.The 105-mm M-7 howitzer motor carriage was not merely a self propelled artillery unit, it was also used for direct fire against hostile vehicles. While not as often as might be thought, this occurred more often than most discussions of armored vehicles indicates. On page 37 of the 93rd Armored Field Artillery Battalion History there is the note:The best shooting in the history of the battalion was enjoyed for the next two days. One tank, and one M-7 were moved up onto the ridge overlooking the valley road and the helpless German column. At a range of less than a thousand yards, these guns blasted at the enemy. They scored hits on enemy ammunition half tracks, thereby jamming traffic on the road so that the battalion was able to smother them with fire.The same unit was also tasked to carry infantry forward on occasion, the same way infantry sometimes road tanks.M-7s were used as tank destroyers and general assault guns in the Pacific.The M-3 Gun Motor Carriage (half track with a 75-mm gun) was first built for the tank destroyers until the M-10 came into service. It is dismissed thereafter by some because in the European theater they were immediately put into the role of artillery support once M-10s came into use. In the Pacific they soldiered on and (while vulnerable to attack) served with the Marines in many battles to secure islands.The M-16 multiple gun motor carriage was a half track with with 4 x .50-caliber machine guns in an open turret on back intended for anti-aircraft use. While it served well for that purpose, it was notorious as the "meat grinder", turning its guns on German positions with devastating effect. German infantry disliked the single .50-caliber machine guns mounted on most USA tanks and gun motor carriages and gun motor carriages - and facing four was enough to cause panic for many.