I sat for several hours with the affable James Edmiston - and still speak to him fairly regularly - about this and other stuff. But factually, we had/saw the first F1 guns in, I would guess in 1968ish and they had Sterling magazines then because the SMG of the time was still the Owen (both of which were being made redundant by our 'new' AR15's). He explained to me that he came away from the meeting legless after a good meal and they came away with the deal of a lifetime. He had just taken over the company at the time and it was the former Sterling Armaments Co* that was bogged down. James had just re-filled the order books and could afford a degree of generosity
*whatever it was called. It had several reincarnations in its life
It would seem highly improbable that the MoS blocked the magazine deal while they weren't the patent holders but, rather the pirates! It'd be like someone trying to sell your car to someone else - when they didn't own it in the first place! Believe me, the MoS had already been pulled sharply into line with massive legal costs and compensation for this foolish piracy by the mid 60's and didn't come back for more argy-bargey with Sterling. David Howroyd called this tpiracy by the MoS their '.....severe arsx kicking' Well, don't mince words David! The real irony was, was that even before the case the two legal teams virtually admitted that the MoS really didn't have a legal leg to stand on. But they STILL carried on. It's easy when it's not your money.......
Sterling had already allowed Canada to manufacture the SMG using their own techniques/methods to suit their needs - with conditions of course and on that basis would seem unlikely to baulk at the magazine too. Making it cheaper would seem to be the obvious or sensible reason.