I have just had a PacNor fitted chambered in 6BR. It has only fired 45 rounds and still being run in so its a bit early to tell how it cleans up at this stage. No load i have put through it has gone over 1/2" at the moment including a load using 5 different types of projectile.
No problem at the time, but now Aust post has added restrictions it maybe a big problem. They usually ship as steel tubes, but if Aust post think that it is a firearm part they will confiscate and you will have done your money.