Unknown rolling block caliber

[tjack]

I suspect your question got lost here in the pistol section. If your chamber cast indicates a .600 NE then it can not be a .58 Berdan. The .600 has a rim dia of approx .805" and the Berdan .740". The .600 has a base dia of approx .697" and the Berdan .646". Remington made Rolling Blocks in the Berdan caliber, both rifle ctgs and carbine ctgs but not the .600 NE. I'm not familiar with commercial Rolling Blocks but at 3.00" case length and OAL of 3.59" it may not chamber; may be too fat and too long.