I read on sites about fire forming, i am assuming this is done by firinf the round through your gun, and that it forms to your chamber. I am also assuming that as long as you are shooting it in the same gun you do not have to full size the cartrigde. Let me now if I got any of this correct.
Thanks in advance
First part you are correct.
Second part your just a little off. Take the 308 win for example. I have found out that you can only neck size about 5 times. Then you need to full length resize the brass. This will also vary by how hot you like your loads. I have some 223 loads pushing 3500 fps. These are for spectacular red misting varmints with 50gr V-Max bulelts. not a candidate for neck sizing.