On the top of the turret it had one browning m2 50. cal machine gun in the turret it had one 75mm tank gun and one browning 30. cal machine gun and in the body it had another browning 30. cal machine gun
The first true machine gun was invented by Hiram Maxim in the United Kingdom.
No published data
light machine gun is the m249 a medium machine gun is the m240 and the heavy machine gun is the browning m2 50. cal machine gun
The first was the gatling gun invented in 1862
50 cal. machine gun. i don't know who decided to use it.
If you are referring to the present, today's most powerful sub-machine gun is the H&K UMP .45 cal sub-machine gun, or the Kriss Vector SMG. if you are referring to the past however then its undeniably the Tommy Gun. also a .45 cal sub-machine gun.
The stick magazine fed hand cranked gatling gun was probably the first machine gun produced.These were in use around 1875-1880.
Maxim
John Moses Browning
The .50 cal Browning Machine Gun cartridge made for the US military with a silver painted tip is Armor Piercing Incendiary
7400 meters.