By Will Dabbs, MD Photos By Sarah DabbsThe LAR PDS is a compact .300 AAC AR pistol incorporating Rock River’s proprietary front-mounted piston-driven operating system. Compact? Yes. Powerful? Very! There isn’t any real reason why anybody would need to pack a .300 AAC AR pocket howitzer in a shoulder rig for personal protection. However, you also don’t need a car capable of doing more than 75 mph, high-speed internet, more than one TV channel, shampoo with conditioner, or ice cream on your apple pie.