I pulled these off of the Iowa Firearms Coalition website forums. Some of these I have no idea about, they were discussed in a thread there. Also the DNR has some places designated as shooting ranges around the state. I put the link to that info at the bottom of this list.
O’Brian County Range northeast of Sheldon near the airport
Spring Run southeast of Spirit Lake (not sure if this one is free)
Ocheyedan west of Spencer on B24
Plymouth county - Oyens north of Oyens on K64. This range has those concrete tubes or did
ML Stub Grey off hwy 31 south of Correctionville on O’Brian Ave (again, not sure this one is free)
I was told of a range north of Plymouth northeast of Mason City close to the junction of S56 and Hwy 9 but I have not been there yet.
Brushy Creek – Hwy 20 to P73 east of Ft Dodge then south on P73. East on D46 north on Brushy creek rd.
Blackhawk Park northwest of Cedar Falls (I haven’t been to this one and I don’t know if it is free)
Bruggerman northeast of Dunkerton (northeast of Waterloo) on Wheeler Rd north off of C66 (again I have not been to this range and don’t know if it is free
Another range I was told about but have not visited is south of Gilbertville (southeast of Waterloo) west off of 218 on Miller Creek Rd
Otter Creek northeast of Tama/Toledo. The area is accessed north off of E43 on N Ave.
Hawkeye Wildlife area northwest of North Liberty turn west off of 965 onto F20
Mastell Bridge off of E28 north west of Anamosa
Scott County Princeton Range north of Princeton right on the Mississippi. North on 67, turn on 285th Ave then east on 266th
Hull – west of Oskaloosa on 92, south on Ford then back east on 260th.