A build-up of residue in primer pockets can cause misfires.
A couple of twists with the RCBS Primer Pocket Brush and residue is easily cleaned out.
Brushes have stainless bristles and interchangeale mounts for large and small primer pockets.

RCBS Primer Pocket Brush Combo comes with Large Brush, Small Brush and a no-roll RCBS Accessory Handle.