Any FFL licenced firearms dealer can order one, although you can't buy one in California. Additionally, you can check Gun Broker, Auction Arms, Guns America, and other websites, although you'll still have to have any firearms you order online received by an FFL licenced dealer.
45 caliber Machine Gun and 50 caliber machine gun
.50 caliber Browning machine guns. A LOT of them!
Mostly all of the paintball guns made today are .68 caliber. Though with the recent changes in paintball some guns are being made with .50 caliber. Though by the year of this gun, it is 100% of .68 caliber.
.50 caliber machine guns, unguided rockets, and unguided bombs.
No. most guns are .68 caliber, however there are some .50 and .43 caliber markers and pistols.
$7,325, they only made 11,870 of them. It was one of the first 50 caliber guns made.
A pair of M2 .50 caliber machine guns.
Caliber refers to the diameter of the bullet. A 50 caliber bullet is .50 of an inch (half an inch) in diameter. It's also used to refer to a gun that shoots a 50 caliber bullet. The problem with the word "caliber" is that it has two different and confusing meanings. In small arms, "caliber" usually refers to the diameter of the bullet, NOT the casing, and is measured in inches (i.e. .50 caliber is 50/100ths of an inch, or a half-inch). [Note: your original question should be ".50" caliber, not "50" caliber.] The biggest problem with this usage is that it's not exact - the most common .50 caliber bullet (the .50 BMG of the Browning .50-caliber Heavy Machinegun) is actually .510 inches at the widest point. The other use of the word caliber is the ratio of the barrel bore (inside) diameter to its length. For instance, the huge 16" guns on the US's Iowa-class battleships are properly classified as 16"/50-caliber guns, which means that the barrel length is 15 times the bore length; thus, the 16/50 is 800 inches long (66 feet, 8 inches). While this usage of caliber is most common for cannon (and not small arms), it nonetheless can be found in discussions of rifles.
Yes.
No such thing. You can have small caliber but not low caliber.
The biggest caliber an American civilian shooter can easily get is .50 BMG. This is the round that .50 Browning machine guns use. There are bigger calibers out there. Some elephant rifles use cartridges that fire a .60 caliber bullet. If you have the right paperwork and permits from the federal government, you can buy a small cannon and shoot 30mm or larger rounds. But among "common" rifle and pistol calibers, the .50 BMG is king of the hill.
Air guns and air rifles come in many sizes. BB guns are .177. Pellet guns & rifles are made in .177, .20, .22, .25, 9MM, 357 Cal, 45 Cal and 50 Caliber. The last four sizes are usually restricted to the PCP (PreCharged Pneumatic) class of air guns. (Big Boar)