Help for identify cartridge case

Hi every one.
I found a cartridge case. It seems like a cal 50 or 12.7 mm or 12.7×77
I will be thankful if give me exact information about that.

If I had to guess, I’d say it is a .50 M48 spotter round.

No real need to guess. You are correct.

12.7x76 M48

Thanks for your helping