300 BO to 204 Ruger

[KnotRight]

I have a carbine length 300 BO for over 3 years and it might have 100 rounds through the barrel. Besides the barrel, what else is needed to change it to a 204 Ruger. I think the magazines are the same (but heard the metal work better). How about the BCG?

 

[telephoneman]

Bcg is the standard 5.56 that you already have. I’m not sure what mags work best for 204.