Non-standardised weaponry may be used by special operations units, or even regular line units as is convenient to do so. For example, in Iraq, we'd often capture RPD, RPK, and PK machine guns, and we'd often employ them if we were in a pitched firefight.
Cost.
there is an unknown amount of guns used by the American army
For the sake of producing a high volume of casualties on the battlefield. Even today, they serve the same function - in a US Army light infantry platoon, for example, the two medium/general purpose machine guns account for 70% of that platoon's overall firepower.
we just talked about this in Social Studies, machine guns, gas masks, and other stuff a can't remember. story of my life.
Ebay, or Toys R Us.
In World War 2, no, not necessarily better in terms of quality and performance, but US guns were simpler, and US industry could produce more of them. German factories worked by slave labor had trouble supplying the German Army with enough guns. In comparing the US M1 Garand rifle with the German Gewher 43, the G43 was actually a superior weapon, but the Germans managed to produce them only by the thousand while the US made over a million M1 rifles. In World War 1, both armies were equipped with guns which were roughly equal to each other, with a few exceptions. For example, the US M1911 pistol was much more rugged for trench warfare than the delicate German P-08. Yet, the Germans had much better machine guns than the horrible French Chauchat which US machine gunners were required to use. US Marines did a bit better, equipped with the British Lewis machine gun which was not perfect but much better than the French machine gun.
They use a lot of guns given them by the US BATF.
The US military and some law enforcement agencies use machineguns. Private collectors that have registered machineguns may also own them in most states.
The lights that com out of guns are only used by police officers and the US army.
no
During the Vietnam War era, "Gun" meant artillery. Small arms meant machine guns, rifles, pistols, etc. Today's "Gun's" in the US Army are hi-tech using smart projectiles and are mostly light weight improved versions from the Viet War. Mostly 105mm's and 155mm. During the Vietnam War the US Army fielded: 175mm self propelled guns; 8 inch self propelled guns; 155mm self propelled guns; 40mm Dusters (WWII pom pom guns AAA); towed 105mm field guns, towed 155mm field guns (referred to as "Split Trails") because the towing portion of the guns were split to support it when firing; put together for towing. US Army tank guns were the 90mm on the M48 Patton tank; 152mm for the M551 Sheridan tank. The US Army infantry in Vietnam initially fielded the M14 rifle, then transitioned onto the M16 rifle. The standard pistol for all GIs was the standard model 1911 .45 automatic. Recoilless rifles operated by the US Army were the 90mm and 106mm. Standard mortars were the 81mm and 4 deuce (4.2 inch mortar).
Tanks use cannons; and aircraft use machine guns or automatic cannons (small caliber such as 20mm, 30mm, etc). Tank cannons are called "main guns." During the Vietnam War, the US Patton tanks fired 90mm main guns; while the Australian Centurion tanks fired 84mm guns.