Did another round today, ran up to 52.5 H1000 (pretty crunchy) and only saw some mild pressure signs at the top (slightly flat primers, light swipe marks. No heavy bolt, no heavy swipes, no craters). Groups were just meh today with both bullets, but the 108 still grouped better than the 106. Magnetospeed on the barrel though, not putting too much stock in a 2 grain span group with the Chrono on.
Big velocity bump from 52.0 (lightly compressed) to 52.5 (moderately compressed. Don't think I'll try to stuff any more in than that). I'm guessing I broke enough kernels to meaningfully change the amount of surface area present, rather than a transition from a "flat spot" or "node" (becoming more and more of the opinion that those don't really exist) to a higher "node" due to charge weight.
I'm planning to try loading 10 at 51.5 or 52.0 and see what kind of groups I get.