Move over Dirty Harry. . .

It's been years since I went into a gun store. I recently purchased a Remington Model 597 .22 caliber rifle for the sole purpose of exterminating a couple of pesky beavers that have moved into the dam of my father's pond. During the paperwork process, I noticed this contraption. Can you say bang? Has anyone shot this thing? And if so, do they still have their arms or hearing?