Some interesting guns from the back yard of the Artillery museum in St.Petersburg. This part is normally not accessible for the visitors

experimental 37-mm quad AA gun, 1959

experimental 76mm automatic AA gun, 1954

25mm quad AA gun, 1948

Thanks Max, I've not seen those before.

I'm curious about that quad 25 mm mounting.  The barrels seem significantly longer than those for the 25 mm/79 2M or the 25 mm 72-K.  I would think that there would be significant dispersion problems with them as they are slender and unsupported.  Also wondering if the traveling brace is missing a piece to support the upper barrels.