Your hunting with basically a generic M4 rifle. The 16 inch barrel will serve you just fine. I've killed lots of coyotes with both the 16 and 20 inch barrels. Most of my shots are at 200 yards or less, the 16 incher with your stock will handle better if your calling them as you may be in brush, edge of a corn field, etc and you can shoulder it easier. If your shooting say--over 200 yards, the 20 incher will help a bit but not so much to not take the shot with your M4. My son has the 1 incher where I have the 20 incher, NOT THAT MUCH DIFFERENCE if you know your abillities. On another matter, I have killed as many coyotes with full metal jackets as with soft points in my 30 years of calling. A soft point traveling at 3200 FPS will drop a "dog" and not tear ;up the hide as much if your going to save it.