Do you believe it's common to get sticky bolts because the load is over pressure?
I've been loading 6MM Remington cases for decades, new cases are fired, neck sized, all cases trimmed to the exact same length then loaded.
Many are shot in excess of 20-25 times and never trimmed or resized, recycled when the neck splits. I have never had a sticky bolt when chambering or extracting a fired case.
Load is a Reloder 19, with 75 grain VMAX at 3,900 FPS, tested pressure on my first barrel was right at max average 65,000 PSI. I had to take the smiths words on that as I was not there. I shot enough rounds, slowly to burn out a barrel. Chucks, deer, no dog towns or competitions.
I believe if your neck sized brass is moving I'd back off pressure. Something's wrong, the heat and pressure is too much for the brass and or the receiver.