222 to 223
How far are you willing to go?
You can have the barrel opened to 223, as it is right now. if it leaves a slight step in the chamber, wich is not unsafe for firing factory cartridges, then setting the barrel back one thread will fix that.
Any changes made to a rifle can change how it shoots. Once changed it is changed, going back, NOT!
For me, something that was my dads or gramppa's is going to stay the way it is right now, and I will find or build the variation on something else if that is what floats my boat. Because changing the connection with the past, takes away from the past,, some will say it makes the connection stronger, That may be if it works, If it doesn't there is an ugly break from the past!