I have seen one from the air by Washington. It sits at most two miles west and just a little south of town. Looks like an asphalt county road. Just west of a railroad underpass and then a little north of the road. I can see the berms but can't tell if there are any benches. I think there is a long one for rifles and a short one for hand guns.
There is another good one that I have actually been to. It is east of Anamosa, somewhere around Stone City? I could drive there but I couldn't tell you how to get there. Its in a State or County Park. It is very nice. Benches with a roof. Rest rooms. It was clean and neat, but that was 3-4 years ago.
Sports Outfitters in CR has an indoor range. I used there hand gun range three years ago. Kinda musty, but functional. They have a range for rifles but don't know how long it is. 16th Ave. way at the west edge of town.
Now that I read back through the post it doesn't sound like much help. Just remember to turn by the old Bennet place and angle off by where the big Oak used to stand before the storm of '56 blew it down and when you get to the old white barn you are there.
The 'Bonker