The Rock Island Armory STK100 is a semi-automatic pistol chambered in 9mm Luger with a 4.5-inch barrel, 17+1 capacity, and a weight of 28.8 oz. The frame and slide are both black anodized aluminum. The slide has an optic cut and serrations. Sights are fixed 3-dot. The frame has a beavertail, lightening cuts, and a Picatinny rail. Action is DA/SA. 
 

Key Specifications 

• Model: STK100 
• Caliber: 9mm Luger (9x19 Para) 
• Barrel Length: 4.5 inches 
• Overall Length: 7.9 inches 
• Capacity: 17+1 rounds 
• Weight: 28.8 oz 
• Frame Material: Aluminum, Black Anodized 
• Slide Material: Aluminum, Black Anodized 
• Sights: Fixed 3-dot 
• Action: DA/SA 
• Rail: Picatinny 
   

Features 

The aluminum frame is the differentiating detail here — most pistols in this class use polymer. The aluminum construction adds rigidity and a different feel in the hand, and the lightening cuts keep the weight manageable at 28.8 oz. 
 
The optic-ready slide accepts a red dot without an adapter plate. The Picatinny rail accommodates lights and lasers. Fixed 3-dot sights are usable as backup when running an optic. 
 
The DA/SA action requires familiarization — the first shot double-action pull is heavier than subsequent single-action pulls. Shooters coming from striker-fired pistols will need to adjust their trigger management.

The Rock Island STK100 gets broadly positive reviews given its price point, with the aluminum frame and optic-ready slide drawing the most interest.

Value is the most frequently cited strength. Buyers report solid build quality and reliable function at range sessions, and the aluminum frame is seen as a genuine differentiator from the sea of polymer-framed competitors at similar prices. The optic-ready slide is popular — many owners mount a red dot and use the fixed sights as backup.

Ergonomics get mixed marks. Grip texture and overall feel vary by hand size, and some users suggest the grip could be improved. The DA/SA action is well-regarded by those familiar with the manual of arms, but occasionally mentioned as a learning curve for newer shooters.

Break-in period comes up in several reviews — some owners note the pistol benefited from 100-200 rounds before achieving consistent reliability. Customer service experiences with Rock Island vary, and parts availability is flagged as a concern for some owners.