here is one way to tell for sure; dude if you are driving down a 2 laner, or highway, or driving in front of some farming/ranching property, and you see oblong/circle-ish looking shapes in short grass, that appears about 5 to 10 feet in diameter, and all turned up, like someone took a plow to it, in just that circular spot, and you start to see several of those spots, you got hogs turning up your ground , baby!!!!
I like the 20 grainers for headshots, and heartshots, I like the 17 grainers for ear/neck shots, turns those parts into a blender...