All rifles I have ever shot with CBs have used gas checks (or paper patching). I am therefore hesitant to go without a checked design. It's one thing cleaning lead out of a short handgun barrel and another chore entirely with a rifle.
Plus the at the greater pressures and smaller diameters (reduced lube) it seems like one should really err with the side of gas checks.
Are there examples though of shooting CBs in rifles at solid rifle velocities/pressures (like 2000 FPS and 40k PSI) without leading?