Having swaged open the chambers on..
RG34, to where a .22Mag can partially chamber, using CCI Mini-mags and Federal Hi-power for plinking.
I would say that most likely you need to chuck a new bore bore in a cordless drill and SLOWLY spin it in each chamber WITH PLENTY OF SOLVENT. Just sounds like the CCI are sticking to the walls possibly due to some residue of using .22 shorts, where the Federal is not sticking as much.
Also, read about the "cool down" period, might be a good idea to back off the rapid fire.
post some pic's!