Last year a fellow guest hunter at a deer camp showed me his allegedly AI'd 300 RUM. He told me of the marvelous velocities he was getting, something like 4000 fps with 180s. I asked to see a piece of fireformed brass and he didn't have any on him. When I asked about load data he said he didn't load any yet. So I had to ask where the velocity numbers came from. According to him when the charge first ignites it generates enough pressure to form the brass to the vastly improved AI configuration. Then the remainder of the charge burns so much more efficiently that it gives the major velocity boost.
mathman
