How many times can brass be used and

[Bassfish1952]

"Is there a neck sizer      out for the 6arc ?"

If there is you should not be interested IMHO. A slight shoulder bump back (.002") & body size, will offer the optimum accuracy.

As precisely round, as your chamber is, it is probably not perfect. With this said if you do not size the body of the brass you would need to clock the brass in the chamber the same,  each time you fire the brass to achieve top accuracy. Perhaps  even to fit the brass in the chamber.

Not sure I understand, after firing I remove the brass casing but if I then put it back in the rifle it will chamber it. After I resize it full length it no longer fits and I have to trim it to fit. So if I neck size it then check case length it should fit everything else should be the same ?

Reason I say this is I took my once fired Hornady brass and ran it thru the action again and it fit . I resized it and it didn't till I tried the neck

Now I have the lee case trimmer that you insert the case tighten down and trim the neck with .  If I take the center depth gauge out and attach to a drill I should be good to anneal ?