The Geissele GDP (Defense Pistol) is a semi-automatic AR-pattern pistol chambered in 5.56 NATO with an 8-inch barrel. The 8-inch short-barreled configuration places this in a restricted transfer category; additional federal paperwork is required. It holds 10+1 rounds and has a black finish throughout. 
 

Key Specifications 

• Brand: Geissele 
• Model: GDP (Defense Pistol) 
• Caliber: 5.56 NATO 
• Action: Semi Auto 
• Capacity: 10+1 
• Barrel Length: 8 inches 
• Color/Finish: Black 
   

Detailed Features 

• 8-inch barrel in an AR-pattern pistol configuration; transfer requires additional federal paperwork 
• 10+1 round capacity 
• Semi-automatic action 
• Black finish throughout 
• Geissele Defense Pistol (GDP) platform

Owners of the Geissele GDP tend to have a clear sense of what they bought: a compact AR-pattern pistol built to Geissele's known quality standard. The 8-inch barrel in 5.56 NATO is a deliberate trade between velocity and size, and most buyers understood that going in.

Build quality draws consistent praise. Geissele's fit and finish reputation carries over to the GDP, and owners note that tolerances feel tight. The trigger, as with most Geissele products, is a frequent highlight.

The 10+1 capacity and the regulatory transfer process are the predictable friction points. Some owners find the paperwork and wait acceptable given the platform; others suggest that buyers who want a higher-capacity option look at the full standard AR-pattern lineup instead. The GDP is a purpose-specific build and the reviews reflect that.