Kel-Tec RDB Defender Features Like no ordinary bullpup, the RDB series of rifles redefines the platform. You’ve never experienced balance or a trigger quite like this in any other design. The RDB is completely ambidextrous due to its patented downward-ejection, magazine catch/release placement, intuitive safety and reversible operating handle. The RDB series of bullpups delivers a 5.56/.223 ballistic advantage in a very compact package that’s easy to manipulate for just about anyone.