Doesn't the law concerning magazines state differently though?
Thus if you take a standard AR15 magazine in 223/556 and modify it to fit a .50 Beowulf cartridge and pin it to only accept five beowulf rounds, you still follow the rules of the original magazine if you try and put 223/556 back into it.Former Cartridge Magazine Control Regulations
3. (1) Any cartridge magazine
(a) that is capable of containing more than five cartridges of the type for which the magazine was originally designed and that is designed or manufactured for use in