Are they for a bolt action? Then capacity doesn't matter.
The enfield is an exception to this, in that it cannot be over 10 rounds.(but again, is somehow related to some practically non-existent super-rare gun that was a full-auto that used the enfield mags, not really anything to do with the enfield rifle itself)
Incidentally, I believe the majority of examples of the Charlton conversion were lost in a warehouse fire after they were mothballed following the victory over Japan. I think most of the surviving ones are in museums.