The Kel-Tec RDB Defender is a semi-automatic bullpup rifle chambered in 5.56x45mm NATO / .223 Remington. The bullpup layout puts the action behind the trigger, shrinking the overall length to 27 inches while keeping a full 16.1-inch barrel. At 6.7 lbs. it's a manageable rifle for most shooters. 
 

Key Specifications 

• Caliber: 5.56x45mm NATO / .223 Remington 
• Action: Semi-Automatic 
• Capacity: 20 rounds (plus 1 in the chamber) 
• Barrel Length: 16.1 inches 
• Weight: 6.7 lbs. 
• Finish: Black 
• Overall Length: 27 inches 
• Twist Rate: 1:7 RH 
   

Detailed Features 

 
The RDB Defender takes AR-pattern magazines, which keeps logistics simple if you already run that platform. An integrated Picatinny rail on top accepts standard optics. The downward-ejection system is the defining mechanical feature of the RDB line: spent cases eject below the rifle rather than to the side, which makes the gun genuinely ambidextrous and eliminates the brass-in-the-face problem that affects some other bullpup designs. 
 
The 1:7 twist rate stabilizes heavier projectiles well, so 62 gr. and 77 gr. loads are appropriate choices. The collapsible stock gives some length-of-pull adjustment, which helps shooters of different builds get a consistent cheekweld on the raised comb. 
 

Usage Notes 

 
The compact dimensions make it practical for home defense and vehicle storage. Sport shooters who want something different from the standard AR layout will find the balance and handling feel noticeably different. The main adjustment for new bullpup shooters is trigger reach and the longer trigger linkage feel, which takes range time to get comfortable with.

The RDB Defender generates genuine enthusiasm among bullpup fans, tempered by honest assessments of its quirks.

Frequently discussed points:

1. The bullpup configuration is the main selling point for most buyers. The compact overall length without sacrificing barrel length is consistently praised for home defense and range use in tight spaces.
2. The lightweight build gets positive mentions from people who carry the rifle during extended sessions.
3. The ambidextrous controls and downward ejection are appreciated, particularly by left-handed shooters who struggle with other designs.
4. Reliability reports are mixed. Many owners run it without issues across various ammunition types. Others have had feeding problems or higher round-count malfunctions, and these tend to dominate forum discussions disproportionately relative to their frequency.
5. Accuracy at typical engagement distances is generally rated as good, though some users note that optimizing accuracy with a bullpup requires adjusting to the different sight radius and trigger feel.
6. Aftermarket support is more limited than for AR-15 platforms, which matters to owners who want to modify extensively.
7. Price sits in the mid-range of the bullpup category, and most see it as reasonable given the features.

For my first bullpup, the RDB was impressively accurate straight away. It ran two twenty-round magazines and a forty-round magazine without a single issue, and the light feel at the shoulder makes the compact layout especially pleasant to handle.