The Kel-Tec RDB Defender is a semi-automatic bullpup rifle chambered in 5.56mm NATO (also compatible with .223 Rem.) with a 16-inch barrel in a 26.1-inch overall length. At 5.9 lbs, the bullpup layout puts 16 inches of barrel into a package shorter than most carbines. The tan Zytel synthetic stock and 4140 steel receiver are finished in salt bath nitride for corrosion resistance. 
 

Key Specifications: 

• Model: RDB Defender 
• Manufacturer: Kel-Tec 
• Caliber: 5.56mm NATO (also compatible with .223 Rem.) 
• Barrel Length: 16 inches 
• Total Length: 26.1 inches 
• Weight: 5.9 lbs (94.4 oz) 
• Capacity: 20 rounds 
• Action Type: Semi-Automatic 
• Finish Color: Tan 
• Receiver Material: 4140 Steel 
• Stock Material & Structure: Synthetic Zytel Bullpup 
• Safety Mechanism: Lever-style safety 
• Twist Rate: 1:7 RH 
   

Detailed Features: 

 
The RDB's forward-ejecting system is notable: spent casings eject downward through a chute below the action rather than to the side, which makes it genuinely ambidextrous with no case deflector needed. Multiple Picatinny rails allow optic and accessory mounting at front and rear positions. The lever-style safety is within thumb reach. The 1:7 twist handles heavier 5.56 loads well. 
 

Usage Scenarios: 

• Home Defense: 26.1 inches overall with a 16-inch barrel is shorter and more manageable in hallways than a standard carbine. 
• Range Shooting: Lightweight and accurate enough for general rifle practice. 
• Tactical Applications: The compact format and customizable rail system work for users who need a short-barreled-equivalent without the NFA paperwork.

The Kel-Tec RDB Defender draws a loyal following on the strength of its compact dimensions and forward-eject design, with recurring complaints about trigger feel and ergonomics.

The bullpup layout is the most consistently praised feature — owners who bought it specifically for the compact format are generally satisfied, and the forward-ejecting system gets real appreciation from left-handed shooters who can run it without modification. Lightweight at 5.9 lbs is also noted positively. Reliability with common 5.56 loads is reported as solid when the rifle is properly maintained. The customization options via the Picatinny rail system are appreciated by owners who want to add optics and accessories.

Trigger pull is the most common complaint. The bullpup action means the trigger linkage is longer, and the RDB's pull is frequently described as heavier and less crisp than users would prefer, especially compared to traditionally-stocked rifles. Ergonomics are polarizing: the bullpup layout works well for some shooters and not at all for others, and there is no easy way to know which camp you fall into without handling one first. Parts availability and aftermarket support are more limited than AR-platform alternatives, which is a practical consideration for long-term ownership.

For buyers who want the compact package and genuinely ambidextrous operation, the RDB Defender delivers. For those who prioritize trigger feel or broad aftermarket support, other platforms make more sense.