As far as I can tell paintballs can move back untill they're jammed even with the plastic ball thingy, like a line could almost go through both centers perpindicular to the feed tube. Then the other paintballs have enough force when I am running and pumping my arms with the gun that they slam into the paintball and it gets by the detent and the process starts over agian. Atleas that is my theory. How hard would it be to get a speedloader with a detent on both sides?