What in the name of all that is holy...a pump-action homemade launcher for 30x29 VOG-17/30 grenades. Well, I'm guessing homemade because it looks like someone dug it out of a bog, but some real thought and work went into that monstrosity. Looks like a fully milled receiver loosely inspired by an M1918 BAR, straight-line stock like the M79 or the T25, looks like the pistol grip and trigger assembly were recycled from something else (but I can't place what), and...hold up, that forward grip looks somehow familiar. That pump grip is chopped out of something else entirely, either an older military rifle or SMG. Maybe a Beretta M1938 (somehow)? The whole thing is both absolutely hacked-together but also well-built and maybe even functional at a glance. I'm thinking this thing has to have come out of an underground arms plant in Chechnya or Georgia or somewhere. I know the criminal element over that way gets pretty creative at times.
No, wait, looking further up this thread I think it has to be some version of the ZiD 23mm you posted earlier. The receiver is too similar to not be, and while it's rusty and has had the furniture replaced, the two have to be related.
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Did some more digging. If your description of the ZiD as a 4-bore 26.5mm is correct we might be looking at something completely different here, 26.5mm is a standard European military flare size and a brief Google safari has turned up at least two long guns chambered for it. The CZ Brno RG-85, which is a single-shot break-action:
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And the utterly baffling 15-shot Polish RGA-86, which looks to be based on the Manville gun, which also came in 26.5mm.
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So here's my guess: the ZiD, much like the RGA-86 (and maybe the RV-85, can't find much detail on that) were 26.5mm riot guns capable of firing flare, smoke or tear gas rounds. Much like how the KS-23 can fire not only buckshot or slugs, but tear gas and flashbang shells. BUT the rounds shown with the rusty monstrosity are absolutely 30x29mm VOG-17/17M/30 grenades, so either someone is playing around or ZiD were trying to rechamber their unsuccessful riot gun for something with a bit more bite.
