If the gun will shoot .5MOA, I don't see a reason to switch the barrels...
What if the barrel is a 1.5 MOA barrel? I would always wonder whether or not it's me or the gun.
I'd hate to spend a lot of time to find out what the gun likes, just to find out that the best it will do is 1.5MOA.
I'm with Hoser: Change it for a barrel of known quality and proven ability.