WASHINGTON (AP) — President Joe Biden is ordering a half-dozen executive actions aimed at addressing what he calls an “epidemic and an international embarrassment” of gun violence in America. But Thursday’s modest moves underscore the limitations of his power to act alone. He faces difficult politics in getting significant firearms legislation passed in Congress. Biden’s actions include a move to crack down on “ghost guns,” homemade firearms that lack serial numbers and are often purchased without a background check. He also announced tighter regulations on pistol-stabilizing braces like the one used in Boulder, Colorado, in a shooting last month that left 10 dead.