The Mountain Billy Gun Lab Goat-15 ATOM is a .22 LR pistol with a 7.8-inch barrel and an MLOK handguard. A rear rail is included for accessory mounting. The AR-15-pattern pistol format puts the controls in a familiar layout without the length of a rifle. 
 

Key Specifications 

• Brand: Mountain Billy Gun Lab 
• Model: Goat-15 ATOM 
• Caliber: .22 LR 
• Action: Semi Auto 
• Barrel Length: 7.8 in 
   

Detailed Features 

• 7.8-inch barrel in a pistol configuration 
• MLOK handguard for accessory attachment 
• Rear accessory rail 
• AR-15-pattern controls and ergonomics 
• .22 LR chambering

Owners of the Goat-15 ATOM appreciate the AR-15-style ergonomics in a compact .22 LR pistol package. The MLOK handguard gets consistent praise for keeping the overall weight down while allowing light and sight accessories to be added without bulk.

The 7.8-inch barrel length is a deliberate trade-off. Shooters who want a plinker that travels easily find the compact size ideal; those expecting rifle-style accuracy at distance note the shorter sight radius takes adjustment. Trigger feel on the ATOM splits opinion, with some owners finding it acceptable for a rimfire pistol and others recommending an aftermarket upgrade early.

Mountain Billy Gun Lab is a smaller manufacturer, and owners who went through the purchase process comment that availability and lead times can be inconsistent. Those who received the pistol generally report solid fit and finish for the price class, though support options are more limited than with larger brands.