The press is making hay out this guy being caught with a .50 caliber rifle. I know that you in the press don't know the difference, and aren't really interested in the difference, but .50 caliber refers to quite a few different cartridges, and there is a large difference between them:
The round most people think of when they hear 50 caliber, is the .50 BMG. This round is used in heavy machine guns and in the Barret rifle. It fires a 647 grain bullet at 3000 feet per second, which equates to over 13,000 foot pounds of force. While there are ways to convert an AR-15 frame to fire this round, such a rifle is not going to be light, and a person will not be able to hide it under a coat.
More likely, the cartridge we are talking about is the .50 Beowolf. It fires a 325 grain bullet at 2,000 feet per second, developing 2900 foot-pounds of force. To compare this, the .30 06, a common round used in hunting, fires a 200 grain bullet at just over 2500 feet per second, thus generating about 2900 foot pounds of force.
There are even pistol cartridges that are technically .50 caliber, such as the .50 Action Express, a pistol round fired by the Desert Eagle. Firing a 325 grain bullet at 1400 feet per second, it develops about 1400 ft/lbs of energy. There is also the .500 Smith and Wesson, firing a 400 grain bullet at 1800 feet per second, and delivering just under 2900 foot pounds of force.
Even the grenade launcher is said to be a 37mm grenade launcher. Except it isn't. The 37mm launcher is not classed as a grenade launcher (destructive device) by the Bureau of Alcohol, Tobacco, Firearms, and Explosives. According to them, it is a FLARE LAUNCHER, and there are not even any grenades available for it, just flares and smoke signaling devices.
In other words, this guy was not in possession of anything out of the ordinary. Heck, I have better weapons in my gun safe. The problem is that the truth here does not fit in with the agenda of the press: create pants-wetting hysteria in the public, so you can influence opinion in an uneducated populous to advance your agenda.