A man look at different rental guns displayed during the Big Sandy Shoot in Mohave CountyBy Steve Holland WASHINGTON (Reuters) – President Barack Obama tried on Thursday to inject recent momentum into efforts to go gun-keep watch over regulation, pleading with U.S. lawmakers to not forget these shot to dying in Newtown, Connecticut three months ago. Amid indicators that he may have to accept a scaled-down version of gun legislation, Obama sounded a be aware of frustration in calling upon American citizens to demand action from the U.S. Congress in the weeks beforehand. He mentioned the regulation's opponents, the highly effective U.S. …