Re: need to trim new brass???
Trimming is a safety measure, and is required to ensure the case mouths don't encroach on the throat too much. The cases will tend to stretch a bit as they go through the firing/reloading cycles. Some calibers are worse about this than others, the intensity of the load as well as the way in which it was resized, and a host of other factors come into this as well. But new brass, right out of the box, should never need to be trimmed or sized. The variation you're seeing there won't be a problem at all.
We (Lapua) do recommend running new brass over an expander mandrel before the first loading, just to uniform neck tension and round out case mouths that may have been dinged or knocked out of round during shipment. Not really a reloading step per se, but just a little due diligence to make sure everything's "right" on that first go-round.