450 is pistol calibers. 550 will do your 223 as well. Along with a whole host of other pistol and rifle calibers. If you were just doing pistol calibers, I'd say 450 good to go.

I reload 9 calibers on a 550B. 223 isn't one of them. I'm too old - old reloaders have a preference for large primers and larger cailber bullets cause we can see them and pick them up easier... I have a ton of 223 brass however I buy lots of mil-surp to shoot up by the case. If I was loading up 223, it would be for some varmint loads or hunting loads and I end up picking up the 7.62x51 if I'm doing those activities. Dillon is highly recommended in my book.