do I need these? I just ordered a 12BR in 6mmbr. Lapua brass will be ordered. With my 12LRPV in 223 all I ever do is neck size. Are the chambers for 6mmbr more critical or will I be able to just neck size my new 6mmbr brass. I do have a neck turning set from Sinclair and will probably go over all the new brass first after trimming all to equalize.