I can shoot a prairie dog with a 3X-9X scope, about as far as I can stretch the .223, on a varmit weight gun. A 4X-12X is even better for small targets a log ways out.
My current .223 was acquired to shoot yotes and foxes, and an occassional ground hog. It's a little CZ American and weighs in at about 7lbs loaded with a sling, and a Leupold 3X-9X AO Compact. At 3X, I can still get on a moving yote at 25yds, and at 9X clearly line up a chuck at 300+.
Having owned a .222/.223 for the last 40 years of some type or another, I know you can cause a lot of varmit funeral's with a fixed 6X scope, right on out to 350-400yds if you guess the range correctly, and know your drop.