You cannot reload a modern centerfire bolt-action rifle without the detachable mag. You can ONLY CHAMBER ONE ROUND. There are ZERO production trapdoor/floorplate/internal mag rifles other than lever-actions.
"Top-loading" can be done with MANY actions; ARs (DI and piston); handguns, bolt guns, and obviously single-shot like the TC Contender.
Lever-action rifles feed into a tubular mag/mag-tube like a shotgun. Either directly into the tube (Henry Rifles) or from a slot in the receiver (Marlin).
Like I said. Internal magazine. Amazing that both you and tsing toe didn't know the term.
https://www.google.com/search?q=int...35i39l2j0l2.5199j0j7&sourceid=chrome&ie=UTF-8