The Kel-Tec RDB is a bullpup semi-automatic rifle chambered in 5.56x45mm NATO / .223 Remington with a 20.5-inch barrel in a 30.4-inch overall package. 
 

Key Specifications 

• Caliber: 5.56x45mm NATO / .223 Remington 
• Action: Semi-Automatic 
• Barrel Length: 20.5 inches 
• Overall Length: 30.4 inches 
• Weight: 6.9 lbs. 
• Capacity: 20 rounds (1 magazine included) 
• Finish: Black 
   

Detailed Features 

The bullpup layout puts the action behind the pistol grip, which is how a 20.5-inch barrel fits in a 30.4-inch overall length. Brass ejects downward rather than to the side, which eliminates the typical lefty-shooter problem with AR-pattern rifles and keeps ejected cases out of other people's space. Controls are fully ambidextrous. The receiver is 4140 steel; the stock and grip are Zytel polymer. Picatinny rails at front and rear positions accept optics and accessories -- there are no built-in sights. 
 

Usage 

The RDB trades the familiar AR layout for a more compact form factor without giving up barrel length. The downward ejection system makes it genuinely ambidextrous. It is a useful option for home defense or range work where a shorter overall footprint matters.

The bullpup layout and resulting compact size are the most-discussed positives. Owners who prioritize maneuverability in tight spaces find it genuinely useful. The downward ejection system draws consistent praise from left-handed shooters and in shared-lane range settings.

Lightweight construction and acceptable accuracy at range are other positives. Affordability compared to other semi-autos in the class is mentioned favorably.

On the downside, reliability concerns appear more often than with more established platforms -- some owners report feeding or cycling issues under certain conditions or with specific ammunition. Trigger quality is the second most common criticism, with many finding the pull heavy or rough compared to AR-15 alternatives. Aftermarket support is limited compared to the AR-15 ecosystem, which frustrates owners who want to customize. Ergonomics are not universally liked -- control placement and stock feel vary between users.