Caldwell 223 5.56 .308 Picatinny Rail Brass Catcher, Black - 530143. The Caldwell Picatinny Rail Brass Catcher offers a convenient, consistent and easy to use method of collecting brass while shooting at the range. Unlike traditional brass catchers that attach using a non-adjustable, flimsy wire frame and one hook-&-loop fastener strap, this variant from Caldwell mounts securely to a .223/5.56 rifle equipped with a Picatinny rail system via a 2-piece aluminum clamp. This brass catcher's frame and clamp are fully adjustable to fit rifles equipped with a variety of optics. Several integral detent locks within the frame can accommodate rifle receivers of varying thicknesses. The brass catcher's nylon mesh bag is heat resistant and features a zipper on the bottom for easy removal of trapped brass. The brass catcher can hold up to 100 empty 5.56x45mm or 223 Rem cases.