Harrell will bore a tuner to fit your barrel.
I doubt if you will see much of a group size change on a CZ, though....I am not downing a CZ, either. I have several 452's and have had others. They are fantastic guns. They are accurate for a sporter. They will hold their own in a sporter benchrest match with most sporters of any make. Howerever, putting a tuner on them will never make them competitive with the heavy barrel target guns or custom built bench guns.