In our army, every weapon except one had a part that was known as the 'master component' which was never available as a spare part. This prevented anyone making a weapon up from spares. The exception was the old .50" short M8C spotting rifle. Not that anyone would find a use for one even if they did make one up! Australiaicon and NZ were the same too. How Canadaicon fared with this quartermasters nightmare is anyones guess.