I used a .30 cal mod on a .243 for years and it was listed on my ticket as '.243 moderator' as well. When I got rid of that particular .243 I wanted it listed as a .30 cal moderator so explained to the FLD that it was suitable 'up to and including'. They re-listed it with no other questions asked. Problem is that the law is so poorly thought out that most RFDs are not going to sell you a .30 cal moderator for use on/to be listed as a smaller cal. for fear of falling foul of the law (or the police interpretation of it).