Explaining American Rifle Ammo Designations

On today's Gun Nuts TV clip, Dave explains the system by which centerfire cartridges are named. I have to admit, I am envious of gun writers like Dave who were smart enough to choose rifles as their primary subject matter. There is a seemingly endless supply of rifle calibers to write about as opposed to only six shotgun gauges.

In an ideal world there would be as many shotgun gauges as there are rifle calibers so I would never run out of column material. I could write "The 15 ½ Gauge vs. the 15.375x76mm" then follow up with "Does Remington's New 13 Gauge make the 12 Obsolete?" Alas, I chose poorly.

Here's Dave to explain cartridge terminology.