Jerry .. there is a fair amount of private farm land around Ritzville but you shouldn't have a problem finding a spot to stump shoot. You might post this in Pow Wow as not too many WA guys visit this forum it seems. I'm a west side guy so I don't know what ranges, clubs might be over there. You might try a PM to James Berry, he lives in Medical Lake just east of Ritzville. There is a wildlife refuge in Cheney you might check out, that's before you get to Spokane and is within reasonable driving distance.
It will most likely be hunting season with some weapon or another when you go, so if you go stump shooting don't have any BH's with you ... late archery season in any of the open units starts around the 25th of Nov
good luck, Ken