I have a Herter's J-9 in 6mm Remington, that I bought new when I was 16 ( now 54). It has been so long since I had a place to shoot, that now I do have a place to shoot and from all I can tell the 6mm Remington is considered obsolete. So what caliber(s) can this mauser actioned rifle be easily converted to? Hopefully with just a barrel replacement and a headspace.