It is for that exact reason the police would never issue a certificate with .22cf.
Calibres are specific, commonly taken a .22rf would grant the authority to purchase .22cap, .22short, .22LR but not .22WMR. There can be no argument that a .22WMR is a rim fire cartridge and has a bullet diameter of .22", however no RFD in their right mind will sell a .22WMR to a certificate holder with the authority to purchase .22LR or .22rf and this is a fact, why? Well because I have tried it and was told by both the RFD & the Police, NO! If anyone has any doubts at all, just go and try to buy .22WMR am