Whichever light machine gun fires the most powerful (in terms of force created when the propellant burns and the gas in the bore expands, pushing the bullet downrange) intermediate rifle cartridge.
As far as most effective, this would be a combination of the bullet design, external ballistics (the bullet's ballistic coefficient; how well it slices through air (effect of drag), how much the bullet is affected by wind, etc.), terminal ballistics (what it does to targets on impact), etc. In short, there is no one answer, as every cartridge has its strengths and weaknesses when compared to other cartridges, or even variants of the same cartridge.
us
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 lever
Eminent Tech TRW 17 is the worlds most powerful subwoofer.
United States Military
the most powerfull locomotive is soviet 2TE126
The Supermarine Spitfire. No question about that.
The United States of America China
500,000 euros
The most powerful light
Jennifer Lopez.
The most powerful light source known is a gamma-ray burst, which is a massive explosion of energy in space. These bursts can emit more light in a few seconds than the sun will emit in its entire lifetime.