Anyone ever tried a small nylon mesh bag supported by a wire frame to catch multiple empties from an auto? I saw a setup like this on an AR-15. The guy was a fox/coyote hunter. He claimed it worked well. A home-made rig.
Jim, such brass catchers have been around, both commercially and homemade for quite a few years. The problem with using one for a shotgun is that it would have to be attached to the gun itself (the handgun catchers come in models attaching to the gun or to the wrist of the shooter).
So, unless there was a real fast way to get the hull out of the "bag" and into a pouch and reload before it was your turn to shoot you would either have four other annoyed squad mates or you would have up to 24 hulls swinging below your gun as you tried to shoot the targets.
Shellcatchers, from rubber bands to plastic or plastic and metal are about the only choice if you want to keep your hulls from hitting the ground.
Tron, for example, installs a little "knob" (he may call it something different) that he regulates to drop your hulls in one spot, but they still hit the ground and lots of clubs, mine included, will not allow you to pick them up.
Piano/Spring wire, .055". It can be had at most hobby shops in sufficient lengths to make enough wires to last for years. Drilling the holes correctly is the first trick. The second is bending the wire properly to stay put and function as intended.
Good advice Quack Shootist. There's more to having one installed properly than just drilling holes in the barrel extension/floating chambers and bending the wire on the ends. Like Quack says, done right, they will last a long time!!