I obtained some empty brass cartridges at an estate sale that I believe are factory rejects or I believe these were pulled from the assembly line, possibly due to an inspection and defects found. They do not have the primmer flash hole in them and some have nicks and dents. I have many caliber cartridges like this that were also obtained at the Estate sale. One that sticks out and I cannot Identify is a case without the primer flash hole that is smaller in diameter at its base than a 223(5.56) and appears to be 20 caliber. It is stamped “R A 6 5”. I have several of them and I also have some 5.56 that are stamped “R A 6 6” which do not have their flash holes but have bullets seated in them. Did Remington attempt to develop a 20 caliber round for the government to use during the Vietnam conflict? I have never seen a cartridge matching the dimensions of the little 20 cal. round. If my eyes are not deceiving me, I measured a primer pocket at .137"; the base of the shell at .332"; the body, just below the shoulder is .321"; case neck length .285"; outside neck diameter is .237"; and inside neck diameter is .212". Any idea what I may have?
PS: Forgot to say that the cases measure between 1.782 and 1.80 in length. I have 5 of them. Most are around the 1.80 length.
Here are pictures of the 20’s beside the 5.56.