It happens with loose and pellet powders.
After one shot it can be a nut wrencher to get the next charge down the bore. A good sealed up ignition system makes it worse due to all of the heat-gasses getting into the bore, VS a loose ignition system that allows a ton of blow by.
Years ago for example i had a Winchester X150 bolt action muzzy and it was filthy due to the slotted breech plug which dumped the primers heat and gasses into the muzzys action. I had zero issues with crud rings and never had to clean the bore between shots, or even after 20+ shots. But once the newer break actions with a tightly sealed up primer came out, it was a new game to learn again.