What powders were you using? Reason I ask is I use to use IMR 4350 for the 270. This was back in the 70's and early 80's. Loads that were good in winter, spring and autumn were hot in summer cause sticky extraction and extremely flat primers. I lived in Victoria, Australia then. Started using AR2209 no problems. No chrony back then so do not know the velocities. The primers when using 2209 were just starting to flatten so I would say it was near max load.