Use a temporary throw rug over your carpet.
Hey posigian, Back many years ago, there was a fine young fellow who used to reload shotgun shells on the living room floor with a Pacific Press. His fine press (which he still has) was mounted to a board which he sat on while reloading. For some reason, there was a slight mishap where some of the Lead Shot got loose and into the popular Shag carpet of that era. His "Honey" was not pleased and he ended up spending a good bit of time trying to find all of the loose #8 pellets.
Couple of weeks pass and the same fiasco repeated itself. After spending LOTS and LOTS of time recovering Lead Shot in the Shag, his "Honey" made him reload on top of a sheet spread over the carpet first. Saved a whole lot of time recovering spills. (Name withheld to avoid "my" embarrassment!)
Being sharp enough to know a good thing (when I'm beat over the head with it), I now have a nice throw rug situated under my Rock Chucker. Every once in awhile something goes bonkers and a bit of powder spills, or a spent primer or two goes onto the rug. It is a simple matter to gather the rug up and go give it a good shaking in the yard. (Do not do this when the "Honey" is at home unless you enjoy snide comments!)
I also would not want to toss "Live Primers" out in the yard, but otherwise, a nice throw rug "on top of your carpet" (while you are reloading) will save you a good bit of grief (verbal too).
Good hunting and clean 1-shot kills, Hot Core