Congrats on your first handloads. Feels great, doesn't it?
I tried one of those stiff mesh tarps like the one in unclebob's link, but it didn't work well on un-even ground and they're too bulky when folded. Plus they grab too much dirt/snow.
I'm looking at a nylon mesh that's big enough to hold centerfire cases, but will be less bulky and less stiff and will not hold as much debris. Something like this;
10'X10' would be about $43. It would fold up a lot smaller and would work better on snow (a big bonus for me).