Back in the 90`s I bought the PiggyBack II Conversion that attaches to the Rock Chucker.
Its a 5 station progressive set up that makes progressive reloading possible. I use it for handgun cartridge reloading and is still in use.
Not for rifle reloading though. It detaches easily making my Rock Chucker a single stage unit for rifle loading.
I dont know if it is still offered by RCBS but I like my set up.
Jim