Ken Buck of Colorado posts video in which he takes a decorative AR-15 rifle off a wall in his Washington DC office and posesA Colorado Republican has posted a video of an AR-15 rifle on the wall of his Washington DC office and dared Democratic frontrunner Joe Biden and his putative gun rights czar Beto O’Rourke to “come and take it”.But reporters, and the internet in general, were quick to point out the weapon would not only usually be illegal under DC law – it also wasn’t loaded.What, one Twitter user asked, was congressman Ken Buck going to do if Biden or O’Rourke did show up looking to take his gun?“Chase Beto around [and] try to poke his eye?”Biden has emerged as the favorite for the Democratic nomination to face Donald Trump at the polls in November. O’Rourke, a former Texas congressman, is one of a number of moderates who initially ran against the former vice-president but have now come out to back him.Last August, O’Rourke’s home town, El Paso, was the scene of a mass shooting a...