I have an R9 in 177 that I shoot generic RWS super dome pellets from as they are available from Bass pro shop and accurate in the gun. I am getting a bit frustrated with it shooting squirrels off my bird feeder at 25 yards, unless I make a head shot it does not kill them fast enough and they run back into the woods. This bothers me as it is tough to get a follow up shot and then the animal dies a slow death, unsporting even on tree rats.

I am thinking of selling my .177 and buying a 20 cal R9.

Is this worth the effort in terms of better lethality?