It happens more often when oils & solvents still exist in there. Just prior to leaving for the range or woods, run both sides of a damp rubbing alcohol patch to remove any oils.

Some solvents make the bore tacky also with sabots. That includes alot of various blackpowder-labeled cleaners. Your bore should be absent of everything before loading that sabot - for easiest loading.

Alot of us use either the MMP three petals or Harvesters crush ribs with those .452 SSTs. Another way to alleviate all that grunting is buying bullets that are.451 -- also purchasing a T-handle or palm-saver for your ramrod.