SL1 the only times I have seen bridging it was in the powder funnel. Happens for me when I am loading with Trail Boss in .30 cal rifle cases. I have to tap the funnel, and case to help settle the powder in. Longer stick powders will do it for me when loading in .22 cal bottle neck cases as well.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.