I’ve used a .177” CO2 pistol loaded with flat-head wadcutter pellets. At “powder burn” range, its power level is academic.
Distract Ratty by pushing a twig or piece of paper through the bars for him to attack; then, when he’s chewing on that, give him the good news in the top of the head. Job done.
(Hint: Place the trap & live rat inside a large plastic bag - l use one of those charity collection bags that come through the letter box about ten times per day - as Ratty will flop and spurt for a good while. Saves cleanup time.)
maximus otter