The Kel-Tec RDB-S is a bullpup semi-automatic rifle chambered in 5.56 NATO / .223 Remington. The bullpup layout puts the action behind the trigger, which gets a 16.1-inch barrel into a 26.1-inch overall package -- about the same length as a typical 10-inch AR pistol with a brace. It weighs 5 lbs 14 oz (94.4 oz) and accepts standard STANAG magazines. The receiver has a salt bath nitride finish. 
 

Key Specifications: 

• Model: RDB-S 
• Caliber: 5.56 NATO / .223 Remington 
• Barrel Length: 16.1 inches 
• Overall Length: 26.1 inches 
• Capacity: 20 rounds (plus one in the chamber) 
• Weight: 5 lbs 14 oz (94.4 oz) 
• Action Type: Semi-Automatic 
• Finish: Black with Salt Bath Nitride on the receiver 
• Safety Type: Manual Lever Safety 
   

Detailed Features: 

The bullpup configuration gives the RDB-S its main advantage: full-length barrel in a package shorter than most conventional rifles. Front and rear sights are folding and adjustable. The synthetic stock is durable and keeps the weight below 6 lbs. The design is ambidextrous, which benefits left-handed shooters who find typical ejection patterns problematic with bullpups. Optics and lights mount via a standard rail.

The Kel-Tec RDB-S draws a generally positive reception with a consistent set of criticisms.

Buyers consistently appreciate the bullpup layout -- the combination of a 16.1-inch barrel in a 26.1-inch package is the core reason most people choose it. Lightweight at under 6 lbs loaded is another regular mention. The ambidextrous design gets specific praise from left-handed shooters, and reliability with a variety of ammunition types is generally reported as adequate.

Critical feedback hits the same notes across most reviews: the trigger is heavier than shooters used to traditional rifles expect, and the bullpup layout requires adjustment time. Aftermarket parts specific to the RDB-S are limited compared to AR-platform rifles, which frustrates buyers who want to customize heavily. A few reviewers question the price-to-performance ratio relative to other compact rifle platforms.

For buyers specifically looking for a compact, lightweight 5.56 bullpup, the RDB-S is one of the few practical options in that market. Those expecting an AR-equivalent trigger feel or aftermarket ecosystem will need to adjust expectations.