Almost everyone cleans the barrel. Almost nobody cleans the action, and it is the part where fouling actually changes how the rifle behaves.
Carbon, unburnt powder, brass shavings and old grease collect in the places a cleaning rod never reaches: the locking lug recesses, the bolt raceway, the back of the chamber, the extractor cut. Build-up in the lug recesses is the one that matters most — it prevents the lugs seating fully and consistently, which means the bolt is closing on a slightly different bearing surface from one shot to the next. That is a repeatability problem masquerading as a load problem, and no amount of barrel cleaning fixes it.
Action cleaning tools exist because the geometry defeats a patch on a jag. They reach into a blind recess, apply pressure where you need it, and pull residue out rather than pushing it deeper into the action.
This is maintenance for the shooter who has already tightened up everything else — the one chasing consistency rather than chasing a first zero. It is also the right move on any rifle that has been shot hard, hunted in dust or snow, or bought used with an unknown history.
Pair it with a solvent appropriate to what you are removing; carbon in an action responds to a dedicated carbon remover, while general grime will come out with a standard bore cleaner.

