That's a pretty opened ended question because of so many variables that are present. Barrels are all different, some have more/less tapering to the lands, and various primers perform at different pressure/pressure curves. And then there are the variables with jackets some heavier/lighter. And distance to lands is variable also.
Personally, I've never had a squib in the 30 or so years of loading metalic, so I can't even relate to this question with experience. But my real concern here is the frequency at which I see squibbs occuring by reloaders , seasoned as well as new guys. I know now days many guys are trying to increase productivity because they shoot a lot. I'm certain if I had a need for high production I would be doing the same thing.
But aren't there some safe guards or fail safe steps and tools that will nearly completely eliminate the occurance? In the same manner by which I've avoided squibbs, can't the standard of looking at each powder charge be incorporated into any process, or not? This topic is important to me because of the alarming number of squibbs that are happening, and some that are resulting in serious injury. And I get the feeling that a lot of the cause is the equipment and not always operator error too, which concerns me even more.