If a shooter is planning on turning the neck on their brass is it best to turn neck before or after fire forming? Also will it do any good to trim the neck on brass that has been fired 5 or 6 times? How much do you trim if you have a chamber that does not require neck trimming before firing? I have never done the neck trimming thing before but have talked to some shooters that say I always trim my neck.
Surrell, if your chamber is for a no Turn neck; I would take off just enough to clean up the cartridge neck about 75% of its surface. Maybe Wynne could post a video of a”clean up” neck turn.
If you know your chamber neck diameter; you will likely have good luck with a neck diameter, with a bullet seated, of 2 thousands less than chamber dimensions. NOTE: Two thousands work for my 6mm and four thousands works in my .284 Shehane.
Im sure that you have figured out by now that knowing chamber dimensions and having the tools and ability to measure your cases and loaded ammo precisely is an absolute must.
Al has very good advice. I would agree that before doing anything to the brass, make sure that you know what the chamber neck size is and not take anymore off the neck than necessary. With that being said, I do think that having all of your match brass the same is important. With the scores and group sizes being shot now days, consistency is a must. I have heard it mentioned that a loaded round .002 to .003 less than neck diameter is about where one needs to be. Good luck. WWE