Powder actuated guns are used to fasten construction materials and fixtures to concrete and steel substrates with hardened steel pins. These guns rely on a controlled powder explosion to forcibly drive the tool's piston onto the head of a specially hardened pin designed to penetrate tough surfaces like steel, concrete or masonry. If you need help deciding which tool (.22 caliber or .27) or which pins to use, we can lend a hand. At Allfasteners, we have decades of experience with helping customers specify the correct tools and hardware for a great variety of jobs. We have backgrounds in building, engineering, safety and many other trades, so the advice you get from us is from first-hand experience.