Unknown .50 cal (military?)

In case the dimensions are difficult to read: OAL 4.08 inch; .500 neck; 1.162 base rim; 2.905 top of extractor groove to neck. No HS, and primer seems larger in diameter than normal large rifle primer.
I hope some member can identify this for me. Thank you. Mike Carrick35

A guess on my part, this seems to be just the body of a plastic bodied case. With the saw-tooth grooves at the head to secure the metal? head to the body. That the “primer pocket” is large would be to allow ample room for the actual vent to work, and to perhaps save a wee-drab of plastic in manufacturing costs?

And it might not be a drawing of a finished or completed case, but just a production stage. Also the mouth being .500 is that an inside or exterior diameter? Or do you know with this being something sent in to ID?

Hope this is of help.

I’m not familiar with the case-type, so ???


How about some photos of that one? Maybe next to a .50 round or case.

Just tossing this out for consideration:


The case body is too big for .50 BMG, closer to 20mm, so could be one of the .60/.50 designs, though I’ve never seen one in a plastic body and metal case head like the drawing alludes to. Common now in the .50 BMG, Mk323 Ball, one company even doing 12.7x108 Russian, but nothing bigger unless you count the 14.5 Russian Plastic Case Dummy from E Germany.

Maybe a 14.5 Steyr?

Mike, it looks like a 20 mm-.50 Anzio, .50 Vulcan or smiliar wildcat based on a 20x102 M103 brass case. What is the neck length?

I want to thank all who helped me with this topic. I am on the staff at The American Rifleman magazine Q&A section, and my “specialty” is the editor sends me questions the other guys don’t want to answer. With this question, I only received the drawing with no comments on plastic or brass shell. The inquirer listed no phone or email, so I’m stuck with snail mail. Again, thanks for all your efforts. Mike.


If you ever make contact with the owner of the drawing and can obtain a photo of the cartridge case & headstamp (if there is one) please post it here as this is a very interesting cartridge case.
Also I hope you will post here on the Forum again, hard question or not!