[Briareos]

Carbine? Interesting...

I've heard the term, "carbine" before, but I never knew that the M4 was a carbine. I thought that it was a conventional rifle.

According to Wikipedia, a carbine, by definition, is a "light, short-barreled rifle." Although, I think that a carbine is designed for combat at a closer range in comparison to a conventional rifle.

I guess a little explanation is in order. Rifle originally referred to rifling the barrel, as opposed to a smoothbore musket. Rifling helped to stabilize the bullet improving long range accuracy, at the expense of being a bigger pain in the butt to load and clean, at least until the development of the so called Minie ball, and eventually breach loading rifles like the Martin-Henrys the British were using at the Battle of Islandlwana.

The definition you're thinking of is basically Cooper's. Cooper made a distinction between things like a AR-15 or Model 94 Winchester, and what he considered true rifles based on the range they were meant to be used at. By his deifinition true rifles were basically bolt actions, while assault rifles fell under carbines. He made the distinction, because they serve very different roles.

In common vernacular it however refers to barrel length. A carbine has a shorter barrel length then standard to increase handiness at the expense of muzzle velocity. Currently that's considered to be around the legal limit established by the National Firearms Act of 1934 at 16" for civilians.