Unidentified draw step

This came in a box of all sorts of cases and other stuff, it is some sort of draw step.

It is brass and berdan primed. The flash holes have not been drilled yet. OAL is 46.65mm. Inside neck diameter is approx. 5mm. Rim looks unfinished. It could possibly be a 5.56 NATO wthat has not had the neck fully necked out yet. Any ideas?

From the photo, it looks like it was intended to be a .223 (5.56 NATO). However, base diameter and the diameter right below the shoulder would be helpful, I would think.

It could also be for 4.85mm couldn’t it?


Base diameter: 9.62mm

Diameter below shoulder: Exactly 9mm

@gravelbelly: The neck is too short for a 4.85mm, I thought that, and compared it to a 4.85 I have here.