I' ve had many a time when I couldn' t reach the stated velocities published in a handbook. The good news is that you' re being a smart handloader and stopping because of the pressure signs and not the published data.

There have been a few times when I went several grains above max.....especially with a .257 Roberts and a .300 H&H.

I sure hope someone posts with an explanation of these things.....but from my perspective " stuff happens" and we may never know why.......but accept that you have done your job well.

Not every question has an answer.