If you read the warning on Hodgdon's site about not loading 296/H110 down more that 3%, it's because of the squibbing out issue. One of their techs once warned me that the warning really applies to any slow-for-application powder can. So Rg1's explanation is, indeed, a mechanism whereby a loading setup that worked fine with your other rounds might be made to produce squib loads.
In general, the slower the powder the nearer to maximum pressure you need to run it to get reliable performance. A heavier bullet gives it more time to build pressure, so that also helps. A magnum primer will increase the starting pressure, which also can help if there's a lot of unused room in the case. Since we don't know your load data or velocities, that's about all I can think to offer on that subject.
If the powder isn't slow, and this is just a fluke of charging, while the loading block suggestion is good, if you are using the turret press in auto-indexing mode that would defeat the purpose of the indexing mechanism (speed). I know several guys have mounted small LED lights over on their presses to get a better view down into the case. It can, in your case, be either at the front or the next station. You just have to remember to look.
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