My CZ like SK ammo, and yes you need to clean them. If you build the carbon ring in front of the chamber, it will swedge the bullet small enough to get thru it. Lead is dead and unless the the muzzle is tighter than the carbon ring, the rifle will not shoot as well as you would hope.
I clean mine after every relay I shoot. With a CZ it has a tighter than normal bore and I have to use a 20 caliber rod to clean it with. A 22 caliber rod does not fit down the bore very well. I use Pro Shot 20 caliber rods, and 3/4 inch patches on a 22 caliber jag. 1 inch patches is too tight to get down the bore. 1 wet patch with Hoppes #9, brass brush (about 5 or 6 strokes), another couple of wet patches and 2 dry patches is my cleaning process.
