A:
This is a subjective question that you will get different answers from different people. The .260 caliber is smaller than the most popular calibers for deer. Some people hunt with quarter-bore guns (versions of the .25 caliber), so it is big enough to kill a deer with a good kill shot.
You also need to check your local wildlife regulations and laws. It's possible it may be deemed too small to be legal for deer hunting in your town, county, or state.