I acquired this projo at a small militaria show this morning and haven’t been able to identify it yet. Any help would be appreciated. The closest similar item I can find in my books is the HE slug for the 42-28mm L Pak. 41. But this one seems substantially larger in size.
Basic measurements are…
Top and bottom flange diameters…51.65mm
Center body diameter…36.9mm
This example has 8 holes around the top flange, unlike the 42-28mm which had 5. It has a similar screw-off windscreen (with 1.5mm pitch threads) but the aluminum dummy fuze or plug is much smaller than the AZ 5072 fuze shown in the manual. The inner cavity contains residue of a brittle, black creosote/tar type filler. The base has a female threaded cavity, presumably for a tracer, unlike the male threaded base of the 42-28mm type.
The only markings I can find on it are two small arrows on either side of the fuze plug wrench flats pointing toward the tip. Nothing at all anywhere on the body, but it’s sort of smooth and rounded like it was polished up at some time long ago, or was carried in someone’s pocket for a couple years. I suppose light markings could have been worn off or they were never there to begin with.
Any ideas? Did the Germans experiment with 52-37mm taper bore ammo? A German round without waffenampts? A U.S. experimental based on a German type?