I'm an avid coyote caller and a gun nut/loonie. My favorite calling guns for brush country is a combo or drilling. My loads are 1 oz of NP BB's in the 2 1/2" 16ga and 1 1/4 oz on the 12ga 2 3/4", while they seem light for coyotes I just use them on the close in stuff as I have the rifle barrel on the same gun. These loads are easy on the gun, the shooters should and hard on the coyotes.
12ga/5.6x50R Magnum
12ga/5.6x52R(22 Savage Highpower)
16ga/16ga/6.5x58R Sauer
These are all with the shotgun barrels