<<Those of the M-16, OTOH being made of very thin aluminum sheet, were not up to the job.>>

Never seen an aluminum M-16 Magazine and I've seen at least thousands. In fact, the issue magazines are quite sturdy. Kind of apples-oranges comparison, as the submachine gun is not a rifle... both have applications in warfare and neither does tho other's job very well. (I do not care at all for the cut-down M16 variants; YMMV)

The Uzi feeds a short straight case directly forward and the magazines remind me of Sten magazines - they only need to hold a cartridge in the general vicinity of the path of the bolt (barrel breeches are actually coned or funneled to aid sloppy feeding). I agree that they are made of thicker metal, but that's not the whole story. The Uzi and Sten magazines are usually intentionally made from non-tempered (probably low carbon) steel that forms into the simple shape very readily - in fact, that lends itself to production in unsophisticated shops.

I believe the M-16 magazines are made from a different grade of steel. Feeding a bottle-necked case at a slight upwards angle out of the magazine into the chamber is a bit more finicky at the magazine end - bent feed lips are not good. I'd bet that it actually takes more force to permanently deform the feed lips on an issue M-16 magazine; it's just that Uzi-Sten requirements for feeding are less involved because of the path of the cartridges from magazine to chamber.

Pistol magazines (my beloved M1911A1 comes to mind) are another story - the geometry involved means that feed lips should be "perfect" or else. Eveyone with more than a couple of pistol magazines has at least one that won't reliably feed. Ironically, the ones I've run across with the best reliability have been WWII era magazines... perhaps only the "good" ones were kept? I function test ALL magazines...

None of them should be used as a bottle cap lifter, eh? I'll keep my SAK (with corkscrew, LoL!) on me...

Regards,

Tom