The RSC 1917 was a french semi automatic battle rifle deployed in WW1, being the first ever semi automatic rifle deployed anywhere.
It had a pretty complicated loading mechanism (as depicted in this contraption) which wasn't handy in the trenches, there were later iterations of the 1917 and then later the 1918 that made this mildly better, but still was a hassle to reload.
It didn't earn a good reputation for its reliability either, it was prone to jamming especially in the muddy trenches of WW1.
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Controls:
Hold main stock piece and press F: fire