As with all Glocks, the model 20 is a single action pistol with no external hammer or safety. the G20 is chambered for the powerful 10mm Auto. It measures 193mm long by 139mm tall and weighs only 28oz empty. A magazine loaded full of 10mm will add another 12 oz to that. In civilian form, maximum capacity is 1 in the chamber, 10 in the clip. Law enforcement gets 5 more rounds, for 16 total. (15 in the magazine, 1 in the pipe.). The 10mm Glock 20 is the most powerful Glock handgun made, accepting loads of Winchester SuperX 175 grain, 1290FPS jacketed hollow points that deliver 647 ft/lbs of muzzle energy. Wow. It's a Dirty Harry magnum for the bad cop of the 21st century.