If they are intended for anti-personnel (that's killing people), they are the same size as rifle bullets. The US .50 round (half-inch bore diameter) was larger and developed after World War 1 for shooting down aircraft, but the Russians and British had even bigger machine guns than that. When the the bore diameter is 20mm or more, it is considered a cannon instead of a machine gun, even if it shoots faster.
The machine gun evolved from the Gattling gun, a device that that rapidly fired bullets when cranked. WWI saw the first true machine guns, liquid and air cooled. http://en.wikipedia.org/wiki/Gatling_gun Another example is the french Mitralleuse, used in the Franco/Prussian war of 1870/71.
Panzers can shoot bullets. Gun bullets.
Machine gun, airplane, rifles, swords/knives, submarines, bullets, chains, barbed wire, tanks
It's when a machine gun enters the nose.
They don't- but are most effective when firing over ground that uniformly slopes away from the gun. This permits "grazing" fire- all bullets travel at the height of a man.
300-a few thousand depending on the machine gun.
Depending on the gun, no limit. A belt fed machine gun can have a belt added to a belt added to a belt.
Fire a lot of bullets very quickly.
The machine gun can shoot 400 to 500 bullets per minute, however, it wasn't that accurate.
They both fire things called 'Bullets'
The question can't be answered as asked. How big/thick is the tree? What kind of tree? What caliber machine gun? What are the specifications of the cartridge being fired? Even with that information, it will be hard to answer.
As few as 2 and upwards of 200
it shoots a lot of bullets in a short time
Ameli Rifles use .45 CAL bullets. This type of ammunition is very expensive to buy however you can get these at your local gun store. Ameli machine guns use .22 rounds that are a lot cheaper.
720 rounds a minute approximately
The Metal Storm is the World's fastest machine gun. It fires 1660 bullets in every second up to 1 million rounds per minute without having someone to crank it up. The Metal Storm can be an unmanned machine gun and can open fire automatically because the computer is operating the machine gun. No other machine gun in the World can fire as fast as the metal storm at that kind of firing speed. Metal Storm is one of the fastest machine gun in the World and can fire more bullets much faster than other machine guns. Metal Storm is not an actual machine gun. It is a volley gun. See the Related Question below for a better discussion of what a real machine gun is, and which has the highest rate of fire.
Bullets. From a gun. Bullets. From a gun.