I also have gone this route. You can shoot cb ammo from any 22 LR revolver. But... Quiet groundhog kills are difficult with CB type ammo. I bought a Remington 512 with a 24" barrel, and CBs are very quiet, but just didnt have the power to humanly kill a GH unless sniper accurate shots are taken.
IF legal in your state, and you are serious about stopping the GH invasion, a suppressed 22 rifle, with standard velocity ammo is very effective, and whisper quiet.
Well... now I see you are in the PRofNJ, so sorry... No suppressor for you. Good luck with the GHs