XDA

The AFP photo to the left carries the following caption: A US marine sniper fires at insurgents with a 50mm caliber gun from a hideout on a rooftop near the town of al-Qaim at the Iraqi-Syrian border, in western Iraq.

Close. It's a .50 caliber rifle (a semi-auto Barrett Model 82). John Wayne at his most macho, pulling grenade rings with his teeth, couldn't fire a 50 mm from his shoulder. No human could.

Let's do some review. Caliber is the diameter of the bullet measured as a percentage of an inch. .50 caliber is a half inch in diameter. That doesn't tell the whole story (but I'll get to that). Millimeter (mm) is one thousandth of a meter. 10 millimeters is a centimeter; 2.54 centimeters is an inch. Most of the European cartridges are in mm. Most of the American cartridges are in caliber. Some of the more successful cartridges have both. The famous 30.06 cartridge (.30 caliber (little less than 1/3 of an inch) first made in 1906) is also known as 7,62 x 63mm in Europe (where they use a comma where we would use a period). The little .223 assault round, which we use in our M-16, is 5,56 x 45mm in Europe).

The Barrett Model 82 is chambered for .50 BMG which is the cartridge developed for the Browning M-2 .50 caliber machine gun (BMG--Browning Machine Gun), our WWII heavy machine gun. It is huge and really the last cartridge a man could fire effectively from his shoulder. After that the next bigger useful cartridge is 20mm. The first German tanks in WWII had a light machine gun and a 20mm at the beginning of the war. By the end of the war they carried the same light machine gun but an 88mm cannon. The automatic gun on wheels that chews up the 101st paratroopers on the faux Tiger tank in Saving Private Ryan was an automatic version of the 20mm cannon. It was on wheels on purpose as there are few hand held 20mm rifles, none of them very successful.

Why is the marine using the .50? The main reason is the the bullet goes a long way accurately. I've seen guys put 10 rounds on a metal disc a foot in diameter from 1,000 yards. Few people could do that with a 30.06. Armed with a .50, you could probably hit someone out to a mile and a half. The second reason is when the bullet gets there, the incredible kinetic energy it carries blows the target up. It's awful, but it's kinda cool too.

Here's why.

The .223 with a little bullet, 45 grains in weight goes fast, 3200 feet per second, but doesn't have a lot of power, just 965 foot pounds of energy You cannot legally hunt deer with .223 in this state; it just isn't powerful enough to kill them outright. The 30.06 kills deer just fine (and men too) if you hit them and its bullet, which weighs, say, 190 grains, goes slower 2700 feet per second but because it weighs more, it packs a bigger hit, 3076 foot pounds of energy. The .50 BMG, with a big 770 grain bullet, goes about as fast, 2769 feet per second but hits with an amazing 12,775 foot pounds of energy. That's why you blow up. Hydrostatic pressure caused by the round hitting the body makes all the blood and other fluids escape the body with explosive force. Parts fly off. Drudge had a link to a video of a .50 BMG sniper hitting a Taliban soldier in Afghanistan a few weeks back but I could never make it work. The teaser still photo was informative enough.