Originally Posted by rjmarine
... but if you have a factory chamber say in 308 you could use 358 brass . when you size the 358 brass down to your 308 you end up with a thicker neck and then you could size this neck to be say .001 - .0015 smaller then the chamber neck.
i hope this helps lol
I've done this with my 7mm RM, shooting in factory Tikka T3 rifles. My brass is head stamped 338 Win Mag. Necked it down and then outside neck turned to clean up about 90% of the case necks. It did help remove some excess clearance between the chamber neck and the outside of the case neck, because the case necks are now a little thicker. Don't gain as much neck thickness as you'd imagine. Seem to recall that neck thickness increased enough that I use a 1 or 2 thou larger diameter neck bushing with the Redding Neck Bushing resizing die.
Dunno if it was a good idea or not. Seems like I've read where some don't think this is a good idea, but it seems to have gone will for me. I annealed the case necks after sizing down. I can say that the seated bullets in these cases are very concentric. Using K&M neck turning tool and mandrels.