You're over thinking it. Not sure there's any difference in force and if so it's negligible. Considering that most eastern European military ammo is not brass and they don't typically baby their equipment. Also, if you look around you'll find tests that have been done on the hardness of brass vs steel case and you'd be surprised that more often than not the brass is as hard and sometimes harder than steel.
Where are you finding cheetah ammo? Nothing on vector's web site about it and I thought Vector closed after that whole selling repackaged Chinese ammo to the US government fiasco
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