Out of interest Jer
screened porch
, where do you have your catch-box situated? I mainly use a catch-box indoors, and so I use plastic slingshot ammo, rather than clay. Used in this way, plastic ammo last virtually forever, and is more accurate, and less messy than clay ammo. I mainly use clay ammo when I am at the back of my house, or in local woods and parks, where steel ammo is potentially unsafe. The main advantages of clay ammo are that it explodes, or at least substantially degrades, on impact, and goes back to being mud, it's very inexpensive, and won't break windows, or hurt stray dogs, but in most cases, the size and weight varies, and it's rarely completely spherical
Just been cleaning out my indoor catch-box. I have a lot of plastic Wasp ammo, so I don't have to do this very often. I lose the odd ball to the vacuum-cleaner, but that's about it
The light clay and plastic balls actually drop much less than steel or lead ammo. Try raising your draw point very slightly 
I've hit my windows many, many times, when scaring off the pigeons in my garden, hit the back of my hand a couple of times too - no damage at all. It won't be long until every shot goes on target, but you still get ricochets 
So my daughter is buying one from simple shot and mailing it forward.
It seems particularly bizarre, considering how easy it is to MAKE a slingshot! 
