https://en.wikipedia.org/wiki/Steyr_AUG
LARPfag here. The StG77 is the only rifle I know, but I can't believe you can ask for more.
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Look through telescope
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Put center of crosshairs over target
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Pull trigger
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See target pop
Muzzle velocity is 970m/s -- no imagination or mental acrobatics required for targets closer than a hundred yards. Aim a palm or so higher for each extra hundred yards. The rifle is mostly made of plastic and absolutely no burden, not even on 30 ml walks. Careful cleaning is a requirement for automatic action, though, especially for and after using blinds.
How does that compare to U.S. army rifles? Or a Kalashnikov? A problem for guerilleros might be that all parts are machine-tooled, so you need special equipment for making spares.
Thinking about it, you can probably cut it with a a tap-and-die [1] like a thread for a screw. (Been there, done that, btw.)
The part in pic looks indeed complicated. Beats me how you make the inside cogs without a CNC mill.
Thanks for your patience. I'm feeling awkward for lack of vocabulary and metalworks knowledge. War is hell. It's an interesting subject, though.
[1] If this makes no sense, I have to look up all the technical terms.