You should be able to handle slightly heavier bullets with a 1:9 twist. Since the target is varmints, I would suggest 55 grains, and ballistic tips are pretty destructive, and then maybe some 60 grainers or so to compare. Each rifle can have kind of a funny appetite for bullets. Some like flat base bullets as opposed to boat-tails, eg. Some like heavy, some like light. It is truly trial and error. But with scope and a Savage rifle, the yote probably does not stand much of a chance unless he gets a sniff at the wrong moment.