Guess Which One?

Which one’s which?

Find the M-16 and the AR-15.

And, did you know?

ALL parts are interchangeable on the M-16 and the AR-15.

Every single one of them.

Why is that?

When Eugene Stoner (1922-1997) of the Armalite corporation originally designed the weapon, it was at the behest of the United States Department of Defense which sought a firearm that was lightweight (under 6 pounds) had a high-capacity magazine (30 rounds), and could penetrate BOTH sides of a steel helmet at 500 yards. It was called the AR15, for Armalite Rifle version 15. There had been several previous iterations to the rifle, all of which were intended exclusively for military use.

The .223 caliber round (the bullet, not the shell/casing) had been introduced to market and made available to the civilian market by Remington, which commercially introduced the .222 Remington as a varmint cartridge in 1950 – a round intended for pest control.

Bullets are measured in size, which is called “caliber,” and refers to its diameter/circumference, and weight, which is measured in “grains.” So, a 60 grain bullet would weigh 3.887935 grams.

Sometimes also called “ball ammo,” bullets so described are lead bullets completely covered with metal, also known as FMJ, or Full Metal Jacket. Unlike hollow point bullets – bullets which have a hollowed-out center – ball ammo/FMJ bullets do not expand upon impact. Instead, they penetrate a target and quite possibly even penetrate the object behind the target.

There are also numerous varieties and shapes of ball ammunition which range from “boat tails,” flat nose (sometimes called dum-dum bullets), and ones with truncated cones. Each shape has a specific use, but all are made for one purpose in mind: Penetration.

Though the years, the development of the .223 caliber round, and the Armalite Rifle proceeded. The military was increasingly interested in both.

In 1957, events began to accelerate with development of both. Eugene Stoner had developed a rifle called the AR-10 in response to the Army’s request for a “small-caliber, high-velocity” (SCHV) cartridge – the entire shell casing and round, filled with gunpowder, a primer, and bullet. And that year, the Infantry Board had agreed upon the preliminary specifications, which called for a 6 pound, select-fire .22″ rifle with a conventional stock and a 20 round magazine. The proposed chambering had to penetrate the standard issue steel helmet, body armor, and a .135″ steel plate at 500 yards, while maintaining the trajectory and accuracy of M2 ball from a M1 Garand, and equaling or exceeding the “wounding” ability of the .30 Carbine.

In January 1963, just as the Vietnam “conflict” was simmering slightly below a boil, U.S. Secretary of Defense Robert McNamara ordered the AR-15 adopted to replace the M14 which had been the standard issue infantry rifle, and standard issue for all branches of service for several years. His decision was based upon