On the range, with iron sites, I had no problem putting 6 of 10 shots quickly into a pie plate at 100 yards. Adding basic optics, it would become scary accurate at typical ranges (25-100 yds) most encountered in the thick Maine woods. Even when working extended ranges (100-300 yds) found when hunting frozen lakes and power lines, the zippy (2,820 FPS in 70 grain loads) .223 could deliver a terminal payload into the vitals of coyotes, bobcats and fox with ease.
The obvious “classic” choice of AR15 is the .223 round mimicking the military 5.56 mm cartridge. With ammo available through a wide selection of manufacturers, it is both cheap and easy to obtain. Bullet grain weights range from 55 to 75 grains providing plenty of room to fine tune your loads to the game animal you intend to pursue. Fox hunting use the 55-grain load to cut down on hide damage. Want to add a little more knockdown power for coyotes upgrade to the 75-grain. Need better performance? Many ammunition companies offer high-end selections to this popular caliber.
Shooting the .223 is a dream for those used to shooting larger calibers as recoil is practically nominal. The basic ballistics of the .223 make it a formidable predator hunting selection. At 100, 200 and 300 yards bullet drop is 0, -4 and -15 inches. Zeroing in the .223 round at 200 yards would make the “kill zone” much bigger and distance calculations easier. Due to its lightweight, shooting long ranges in windy conditions may require significant windage calculations.
For the survivalist minded crowd, the AR15 is “THE” rifle to own (http://www.shtfblog.com/shtf-blogs-top-ten-best-guns-for-survival/). Available in apocalypse, world ending 30 round clips and zombie horde stomping100 round drums, make it additionally a serious home defense weapon.