text:  any of your AR frames, but the key here is to go to why 11 1⁄2 inch for 5.56? Why not shorter? Why not longer? Well, if a 10-inch gun is... A 10-inch gun is 4% shorter from muzzle to butt than an 11-inch gun, but it has 40% less dwell time. And that dwell time really is assisting the cycling of the gun. It's making it more forgiving to...